ModernGL#

ModernGL is a high performance rendering module for Python.

Install#

From PyPI (pip)#

ModernGL is available on PyPI for Windows, OS X and Linux as pre-built wheels. No complication is needed unless you are setting up a development environment.

$ pip install moderngl

Verify that the package is working:

$ python -m moderngl
moderngl 5.6.0
--------------
vendor: NVIDIA Corporation
renderer: GeForce RTX 2080 SUPER/PCIe/SSE2
version: 3.3.0 NVIDIA 441.87
python: 3.7.6 (tags/v3.7.6:43364a7ae0, Dec 19 2019, 00:42:30) [MSC v.1916 64 bit (AMD64)]
platform: win32
code: 330

Note

If you experience issues it’s probably related to context creation. More configuration might be needed to run moderngl in some cases. This is especially true on linux running without X. See the context section.

Development Environment#

Ideally you want to fork the repository first.

# .. or clone for your fork
git clone https://github.com/moderngl/moderngl.git
cd moderngl

Building on various platforms:

On Windows you need visual c++ build tools installed: https://visualstudio.microsoft.com/visual-cpp-build-tools/
On OS X you need X Code installed + command line tools (xcode-select --install)
Building on linux should pretty much work out of the box
To compile moderngl: python setup.py build_ext --inplace

Package and dev dependencies:

Install requirements.txt, tests/requirements.txt and docs/requirements.txt
Install the package in editable mode: pip install -e .

Using with Mesa 3D on Windows#

If you have an old Graphics Card that raises errors when running moderngl, you can try using this method, to make Moderngl work.

There are essentially two ways,

Compiling Mesa yourselves see https://docs.mesa3d.org/install.html.
Using msys2, which provides pre-compiled Mesa binaries.

Using MSYS2#

Download and Install https://www.msys2.org/#installation
Check whether you have 32-bit or 64-bit python.

32-bit python#

If you have 32-bit python, then open C:\msys64\mingw32.exe and type the following

pacman -S mingw-w64-i686-mesa

It will install mesa and its dependencies. Then you can add C:\msys64\mingw32\bin to PATH before C:\Windows and moderngl should be working. Also, you should set an environment variable called GLCONTEXT_WIN_LIBGL which contains the path to opengl32 dll from mesa. In this case it should be GLCONTEXT_WIN_LIBGL=C:\msys64\mingw32\bin\opengl32.dll.

64-bit python#

If you have 64-bit python, then open C:\msys64\mingw64.exe and type the following

pacman -S mingw-w64-x86_64-mesa

It will install mesa and it’s dependencies. Then you can add C:\msys64\mingw64\bin to PATH before C:\Windows and moderngl should be working. Also, you should set an environment variable called GLCONTEXT_WIN_LIBGL which contains the path to opengl32 dll from mesa. In this case it should be GLCONTEXT_WIN_LIBGL=C:\msys64\mingw64\bin\opengl32.dll

Using ModernGL in CI#

Windows CI Configuration#

ModernGL can’t be run directly on Windows CI without the use of Mesa. To get ModernGL running you should first install Mesa from the MSYS2 project and adding it to the PATH.

Steps#

Usually MSYS2 project should be installed by default by your CI provider in C:\msys64. You can refer the documentation on how to get it installed and make sure to update it.
Then login through bash and enter pacman -S --noconfirm mingw-w64-x86_64-mesa.
```
C:\msys64\usr\bin\bash -lc "pacman -S --noconfirm mingw-w64-x86_64-mesa"
```
This will install Mesa binary, which moderngl would be using.
Then add C:\msys64\mingw64\bin to PATH.

$env:PATH = "C:\msys64\mingw64\bin;$env:PATH"
Warning

Make sure to delete C:\msys64\mingw64\bin\python.exe if it exists because the python provided by them would then be added to Global and some unexpected things may happen.

Then set an environment variable GLCONTEXT_WIN_LIBGL=C:\msys64\mingw64\bin\opengl32.dll. This will make glcontext use C:\msys64\mingw64\bin\opengl32.dll for opengl drivers.
Then you can run moderngl as you want to.

Example Configuration#

A example configuration for Github Actions:

name: Hello World
on: [push, pull_request]

jobs:
  build:
    runs-on: windows-latest
    steps:
      - uses: actions/checkout@v2
      - name: Set up Python
        uses: actions/setup-python@v2
        with:
          python-version: 3.9
      - uses: msys2/setup-msys2@v2
        with:
          msystem: MINGW64
          release: false
          install: mingw-w64-x86_64-mesa
      - name: Test using ModernGL
        shell: pwsh
        run: |
          Remove-Item C:\msys64\mingw64\bin\python.exe -Force
          $env:GLCONTEXT_WIN_LIBGL = "C:\msys64\mingw64\bin\opengl32.dll"
          python -m pip install -r requirements.txt
          python -m pytest

Linux#

For running ModernGL on Linux CI, you would need to configure xvfb so that it starts a Window in the background. After that, you should be able to use ModernGL directly.

Steps#

Install xvfb from Package Manager.
```
sudo apt-get -y install xvfb
```
The run the below command, to start Xvfb from background.
```
sudo /usr/bin/Xvfb :0 -screen 0 1280x1024x24 &
```
You can run ModernGL now.

Example Configuration#

A example configuration for Github Actions:

name: Hello World
on: [push, pull_request]

jobs:
  build:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v2
      - name: Set up Python
        uses: actions/setup-python@v2
        with:
          python-version: 3.9
      - name: Prepare
        run: |
            sudo apt-get -y install xvfb
            sudo /usr/bin/Xvfb :0 -screen 0 1280x1024x24 &
      - name: Test using ModernGL
        run: |
          python -m pip install -r requirements.txt
          python -m pytest

macOS#

You won’t need any special configuration to run on macOS.

The Guide#

An introduction to OpenGL#

The simplified story#

OpenGL (Open Graphics Library) has a long history reaching all the way back to 1992 when it was created by Silicon Graphics. It was partly based in their proprietary IRIS GL (Integrated Raster Imaging System Graphics Library) library.

Today OpenGL is managed by the Khronos Group, an open industry consortium of over 150 leading hardware and software companies creating advanced, royalty-free, acceleration standards for 3D graphics, Augmented and Virtual Reality, vision and machine learning

The purpose of OpenGL is to provide a standard way to interact with the graphics processing unit to achieve hardware accelerated rendering across several platforms. How this is done under the hood is up to the vendors (AMD, Nvidia, Intel, ARM .. etc) as long as the the specifications are followed.

OpenGL have gone though many versions and it can be confusing when looking up resources. Today we separate “Old OpenGL” and “Modern OpenGL”. From 2008 to 2010 version 3.x of OpenGL evolved until version 3.3 and 4.0 was released simultaneously.

In 2010 version 3.3, 4.0 and 4.1 was released to modernize the api (simplified explanation) creating something that would be able to utilize Direct3D 11-class hardware. OpenGL 3.3 is the first “Modern OpenGL” version (simplified explanation). Everything from this version is forward compatible all the way to the latest 4.x version. An optional deprecation mechanism was introduced to disable outdated features. Running OpenGL in core mode would remove all old features while running in compatibility mode would still allow mixing the old and new api.

Note

OpenGL 2.x, 3.0, 3.1 and 3.2 can of course access some modern OpenGL features directly, but for simplicity we are are focused on version 3.3 as it created the final standard we are using today. Older OpenGL was also a pretty wild world with countless vendor specific extensions. Modern OpenGL cleaned this up quite a bit.

In OpenGL we often talk about the Fixed Pipeline and the Programmable Pipeline.

OpenGL code using the Fixed Pipeline (Old OpenGL) would use functions like glVertex, glColor, glMaterial glMatrixMode, glLoadIdentity, glBegin, glEnd, glVertexPointer, glColorPointer, glPushMatrix and glPopMatrix. The api had strong opinions and limitations on what you could do hiding what really went on under the hood.

OpenGL code using the Programmable Pipeline (Modern OpenGL) would use functions like glCreateProgram, UseProgram. glCreateShader, VertexAttrib*, glBindBuffer*, glUniform*. This API mainly works with buffers of data and smaller programs called “shaders” running on the GPU to process this data using the OpenGL Shading Language (GLSL). This gives enormous flexibility but requires that we understand the OpenGL pipeline (actually not that complicated).

Beyond OpenGL#

OpenGL has a lot of “baggage” after 25 years and hardware have drastically changed since its inception. Plans for “OpenGL 5” was started as the Next Generation OpenGL Initiative (glNext). This Turned into the Vulkan API and was a grounds-up redesign to unify OpenGL and OpenGL ES into one common API that will not be backwards compatible with existing OpenGL versions.

This doesn’t mean OpenGL is not worth learning today. In fact learning 3.3+ shaders and understanding the rendering pipeline will greatly help you understand Vulkan. In most cases you can pretty much copy paste the shaders over to Vulkan.

Where do ModernGL fit into all this?#

The ModernGL library exposes the Programmable Pipeline using OpenGL 3.3 core or higher. However, we don’t expose OpenGL functions directly. Instead we expose features though various objects like Buffer and Program in a much more “pythonic” way. It’s in other words a higher level wrapper making OpenGL much easier to reason with. We try to hide most of the complicated details to make the user more productive. There are a lot of pitfalls with OpenGL and we remove most of them.

Learning ModernGL is more about learning shaders and the OpenGL pipeline.

Creating a Context#

Before we can do anything with ModernGL we need a Context. The Context object makes us able to create OpenGL resources. ModernGL can only create headless contexts (no window), but it can also detect and use contexts from a large range of window libraries. The moderngl-window library is a good start or reference for rendering to a window.

Most of the example code here assumes a ctx variable exists with a headless context:

# standalone=True makes a headless context
ctx = moderngl.create_context(standalone=True)

Detecting an active context created by a window library is simply:

ctx = moderngl.create_context()

More details about context creation can be found in the Context Creation section.

ModernGL Types#

Before throwing you into doing shaders we’ll go through some of the most important types/objects in ModernGL.

Buffer is an OpenGL buffer we can for example write vertex data into. This data will reside in graphics memory.
Program is a shader program. We can feed it GLSL source code as strings to set up our shader program
VertexArray is a light object responsible for communication between Buffer and Program so it can understand how to access the provided buffers and do the rendering call. These objects are currently immutable but are cheap to make.
Texture, TextureArray, Texture3D and TextureCube represents the different texture types. Texture is a 2d texture and is most commonly used.
Framebuffer is an offscreen render target. It supports different attachments types such as a Texture and a depth texture/buffer.

All of the objects above can only be created from a Context object:

The ModernGL types cannot be extended as in; you cannot subclass them. Extending them must be done through substitution and not inheritance. This is related to performance. Most objects have an extra property that can contain any python object.

Shader Introduction#

Shaders are small programs running on the GPU (Graphics Processing Unit). We are using a fairly simple language called GLSL (OpenGL Shading Language). This is a C-style language, so it covers most of the features you would expect with such a language. Control structures (for-loops, if-else statements, etc) exist in GLSL, including the switch statement.

Note

The name “shader” comes from the fact that these small GPU programs was originally created for shading (lighting) 3D scenes. This started as per-vertex lighting when the early shaders could only process vertices and evolved into per-pixel lighting when the fragment shader was introduced. They are used in many other areas today, but the name have stuck around.

Examples of types are:

bool value = true;
int value = 1;
uint value = 1;
float value = 0.0;
double value = 0.0;

Each type above also has a 2, 3 and 4 component version:

// float (default) type
vec2 value = vec2(0.0, 1.0);
vec3 value = vec3(0.0, 1.0, 2.0);
vec4 value = vec4(0.0);

// signed and unsigned integer vectors
ivec3 value = ivec3(0);
uvec3 value = ivec3(0);
// etc ..

More about GLSL data types can be found in the Khronos wiki.

The available functions are for example: radians, degrees sin, `cos, tan, asin, acos, atan, pow exp, log, exp2, log2, sqrt, inversesqrt, abs, sign, floor, ceil, fract, mod, min, max, clamp, mix, step, smoothstep, length, distance, dot, cross, normalize, faceforward, reflect, refract, any, all etc.

All functions can be found in the OpenGL Reference Page (exclude functions starting with gl). Most of the functions exist in several overloaded versions supporting different data types.

The basic setup for a shader is the following:

#version 330

void main() {
}

The #version statement is mandatory and should at least be 330 (GLSL version 3.3 matching OpenGL version 3.3). The version statement should always be the first line in the source code. Higher version number is only needed if more fancy features are needed. By the time you need those you probably know what you are doing.

What we also need to realize when working with shaders is that they are executed in parallel across all the cores on your GPU. This can be everything from tens, hundreds, thousands or more cores. Even integrated GPUs today are very competent.

For those who have not worked with shaders before it can be mind-boggling to see the work they can get done in a matter of microseconds. All shader executions / rendering calls are also asynchronous running in the background while your python code is doing other things (but certain operations can cause a “sync” stalling until the shader program is done)

Vertex Shader (transforms)#

Let’s get our hands dirty right away and jump into it by showing the simplest forms of shaders in OpenGL. These are called transforms or transform feedback. Instead of drawing to the screen we simply capture the output of a shader into a Buffer.

The example below shows shader program with only a vertex shader. It has no input data, but we can still force it to run N times. The gl_VertexID (int) variable is a built-in value in vertex shaders containing an integer representing the vertex number being processed.

Input variables in vertex shaders are called attributes (we have no inputs in this example) while output values are called varyings.

import struct
import moderngl

ctx = moderngl.create_context(standalone=True)

program = ctx.program(
    vertex_shader="""
    #version 330

    // Output values for the shader. They end up in the buffer.
    out float value;
    out float product;

    void main() {
        // Implicit type conversion from int to float will happen here
        value = gl_VertexID;
        product = gl_VertexID * gl_VertexID;
    }
    """,
    # What out varyings to capture in our buffer!
    varyings=["value", "product"],
)

NUM_VERTICES = 10

# We always need a vertex array in order to execute a shader program.
# Our shader doesn't have any buffer inputs, so we give it an empty array.
vao = ctx.vertex_array(program, [])

# Create a buffer allocating room for 20 32 bit floats
buffer = ctx.buffer(reserve=NUM_VERTICES * 8)

# Start a transform with buffer as the destination.
# We force the vertex shader to run 10 times
vao.transform(buffer, vertices=NUM_VERTICES)

# Unpack the 20 float values from the buffer (copy from graphics memory to system memory).
# Reading from the buffer will cause a sync (the python program stalls until the shader is done)
data = struct.unpack("20f", buffer.read())
for i in range(0, 20, 2):
    print("value = {}, product = {}".format(*data[i:i+2]))

Output the program is:

value = 0.0, product = 0.0
value = 1.0, product = 1.0
value = 2.0, product = 4.0
value = 3.0, product = 9.0
value = 4.0, product = 16.0
value = 5.0, product = 25.0
value = 6.0, product = 36.0
value = 7.0, product = 49.0
value = 8.0, product = 64.0
value = 9.0, product = 81.0

The GPU is at the very least slightly offended by the meager amount work we assigned it, but this at least shows the basic concept of transforms. We would in most situations also not read the results back into system memory because it’s slow, but sometimes it is needed.

This shader program could for example be modified to generate some geometry or data for any other purpose you might imagine useful. Using modulus (mod) on gl_VertexID can get you pretty far.

Rendering#

import moderngl
import numpy as np

from PIL import Image

ctx = moderngl.create_standalone_context()

prog = ctx.program(
    vertex_shader='''
        #version 330

        in vec2 in_vert;
        in vec3 in_color;

        out vec3 v_color;

        void main() {
            v_color = in_color;
            gl_Position = vec4(in_vert, 0.0, 1.0);
        }
    ''',
    fragment_shader='''
        #version 330

        in vec3 v_color;

        out vec3 f_color;

        void main() {
            f_color = v_color;
        }
    ''',
)

x = np.linspace(-1.0, 1.0, 50)
y = np.random.rand(50) - 0.5
r = np.ones(50)
g = np.zeros(50)
b = np.zeros(50)

vertices = np.dstack([x, y, r, g, b])

vbo = ctx.buffer(vertices.astype('f4').tobytes())
vao = ctx.simple_vertex_array(prog, vbo, 'in_vert', 'in_color')

fbo = ctx.simple_framebuffer((512, 512))
fbo.use()
fbo.clear(0.0, 0.0, 0.0, 1.0)
vao.render(moderngl.LINE_STRIP)

Image.frombytes('RGB', fbo.size, fbo.read(), 'raw', 'RGB', 0, -1).show()

Program#

ModernGL is different from standard plotting libraries. You can define your own shader program to render stuff. This could complicate things, but also provides freedom on how you render your data.

Here is a sample program that passes the input vertex coordinates as is to screen coordinates.

Screen coordinates are in the [-1, 1], [-1, 1] range for x and y axes. The (-1, -1) point is the lower left corner of the screen.

The program will also process a color information.

Entire source

import moderngl

ctx = moderngl.create_standalone_context()

prog = ctx.program(
    vertex_shader='''
        #version 330

        in vec2 in_vert;
        in vec3 in_color;

        out vec3 v_color;

        void main() {
            v_color = in_color;
            gl_Position = vec4(in_vert, 0.0, 1.0);
        }
    ''',
    fragment_shader='''
        #version 330

        in vec3 v_color;

        out vec3 f_color;

        void main() {
            f_color = v_color;
        }
    ''',
)

Vertex Shader

in vec2 in_vert;
in vec3 in_color;

out vec3 v_color;

void main() {
    v_color = in_color;
    gl_Position = vec4(in_vert, 0.0, 1.0);
}

Fragment Shader

in vec3 v_color;

out vec3 f_color;

void main() {
    f_color = v_color;
}

Proceed to the next step.

VertexArray#

import moderngl
import numpy as np

ctx = moderngl.create_standalone_context()

prog = ctx.program(
    vertex_shader='''
        #version 330

        in vec2 in_vert;
        in vec3 in_color;

        out vec3 v_color;

        void main() {
            v_color = in_color;
            gl_Position = vec4(in_vert, 0.0, 1.0);
        }
    ''',
    fragment_shader='''
        #version 330

        in vec3 v_color;

        out vec3 f_color;

        void main() {
            f_color = v_color;
        }
    ''',
)

x = np.linspace(-1.0, 1.0, 50)
y = np.random.rand(50) - 0.5
r = np.ones(50)
g = np.zeros(50)
b = np.zeros(50)

vertices = np.dstack([x, y, r, g, b])

vbo = ctx.buffer(vertices.astype('f4').tobytes())
vao = ctx.simple_vertex_array(prog, vbo, 'in_vert', 'in_color')

Proceed to the next step.

Topics#

The Lifecycle of a ModernGL Object#

From moderngl 5.7 we support three different garbage collection modes. This should be configured using the Context.gc_mode attribute preferably right after the context is created.

The current supported modes are:

None: (default) No garbage collection is performed. Objects needs to to be manually released like in previous versions of moderngl.
"context_gc": Dead objects are collected in Context.objects. These can periodically be released using Context.gc().
"auto": Dead objects are destroyed automatically like we would expect in python.

It’s important to realize here that garbage collection is not about the python objects itself, but the underlying OpenGL objects. ModernGL operates in many different environments were garbage collection can be a challenge. This depends on factors like who is controlling the existence of the OpenGL context and challenges around threading in python.

Standalone / Headless Context#

In this instance we control when the context is created and destroyed. Using "auto" garbage collection is perfectly reasonable in this situation.

Context Detection#

When detecting an existing context from some window library we have no direct control over the existence of the context. Using "auto" mode is dangerous can can cause crashes especially on application exit. The window and context is destroyed and closed, then moderngl will try to destroy resources in a context that no longer exists. Use "context_gc" mode to avoid this.

It can be possible to switch the gc_mode to None when the window is closed. This can still be a problem if you have race conditions due to resources being created in the render loop.

The Threading Issue#

When using threads in python the garbage collector can run in any thread. This is a problem for OpenGL because only the main thread is allowed to interact with the context. When using threads in your application you should be using "context_gc" mode and periodically call Context.gc for example during every frame swap.

Manually Releasing Objects#

Objects in moderngl don’t automatically release the OpenGL resources when gc_mode=None is used. Each type has a release() method that needs to be called to properly clean up everything:

# Create a texture
texture = ctx.texture((10, 10), 4)

# Properly release the opengl resources
texture.release()

Detecting Released Objects#

If you for some reason need to detect if a resource was released it can be done by checking the type of the internal moderngl object (.mglo property):

>> import moderngl
>> ctx = moderngl.create_standalone_context()
>> buffer = ctx.buffer(reserve=1024)
>> type(buffer.mglo)
<class 'mgl.Buffer'>
>> buffer.release()
>> type(buffer.mglo)
<class '_moderngl.InvalidObject'>
>> type(buffer.mglo) == moderngl.mgl.InvalidObject
True

Context Creation#

Note

From moderngl 5.6 context creation is handled by the glcontext package. This makes expanding context support easier for users lowering the bar for contributions. It also means context creation is no longer limited by a moderngl releases.

Note

This page might not list all supported backends as the glcontext project keeps evolving. If using anything outside of the default contexts provided per OS, please check the listed backends in the glcontext project.

Introduction#

A context is an object giving moderngl access to opengl instructions (greatly simplified). How a context is created depends on your operating system and what kind of platform you want to target.

In the vast majority of cases you’ll be using the default context backend supported by your operating system. This backend will be automatically selected unless a specific backend parameter is used.

Default backend per OS

Windows: wgl / opengl32.dll
Linux: x11/glx/libGL
OS X: CGL

These default backends support two modes:

Detecting an exiting active context possibly created by a window library such as glfw, sdl2, pyglet etc.
Creating a headless context (No visible window)

Detecting an existing active context created by a window library:

import moderngl
# Create the window with an OpenGL context (Most window libraries support this)
ctx = moderngl.create_context()
# If successful we can now render to the window
print("Default framebuffer is:", ctx.screen)

A great reference using various window libraries can be found here: https://github.com/moderngl/moderngl-window/tree/master/moderngl_window/context

Creating a headless context:

import moderngl
# Create the context
ctx = moderngl.create_context(standalone=True)
# Create a framebuffer we can render to
fbo = ctx.simple_framebuffer((100, 100), 4)
fbo.use()

Require a minimum OpenGL version#

ModernGL only support 3.3+ contexts. By default version 3.3 is passed in as the minimum required version of the context returned by the backend.

To require a specific version:

moderngl.create_context(require=430)

This will require OpenGL 4.3. If a lower context version is returned the context creation will fail.

This attribute can be accessed in Context.version_code and will be updated to contain the actual version code of the context (If higher than required).

Specifying context backend#

A backend can be passed in for more advanced usage.

For example: Making a headless EGL context on linux:

ctx = moderngl.create_context(standalone=True, backend='egl')

Note

Each backend supports additional keyword arguments for more advanced configuration. This can for example be the exact name of the library to load. More information in the glcontext docs.

Context Info#

Various information such as limits and driver information can be found in the info property. It can often be useful to know the vendor and render for the context:

>>> import moderngl
>>> ctx = moderngl.create_context(standalone=True, gl_version=(4.6))
>>> ctx.info["GL_VENDOR"]
'NVIDIA Corporation'
>>> ctx.info["GL_RENDERER"]
'GeForce RTX 2080 SUPER/PCIe/SSE2'
>>> ctx.info["GL_VERSION"]
'3.3.0 NVIDIA 456.71'

Note that it reports version 3.3 here because ModernGL by default requests a version 3.3 context (minimum requirement).

Texture Format#

Description#

The format of a texture can be described by the dtype parameter during texture creation. For example the moderngl.Context.texture(). The default dtype is f1. Each component is an unsigned byte (0-255) that is normalized when read in a shader into a value from 0.0 to 1.0.

The formats are based on the string formats used in numpy.

Some quick example of texture creation:

# RGBA (4 component) f1 texture
texture = ctx.texture((100, 100), 4)  # dtype f1 is default

# R (1 component) f4 texture (32 bit float)
texture = ctx.texture((100, 100), 1, dype="f4")

# RG (2 component) u2 texture (16 bit unsigned integer)
texture = ctx.texture((100, 100), 2, dtype="u2")

Texture contents can be passed in using the data parameter during creation or by using the write() method. The object passed in data can be bytes or any object supporting the buffer protocol.

When writing data to texture the data type can be derived from the internal format in the tables below. f1 textures takes unsigned bytes (u1 or numpy.uint8 in numpy) while f2 textures takes 16 bit floats (f2 or numpy.float16 in numpy).

Float Textures#

f1 textures are just unsigned bytes (8 bits per component) (GL_UNSIGNED_BYTE)

The f1 texture is the most commonly used textures in OpenGL and is currently the default. Each component takes 1 byte (4 bytes for RGBA). This is not really a “real” float format, but a shader will read normalized values from these textures. 0-255 (byte range) is read as a value from 0.0 to 1.0 in shaders.

In shaders the sampler type should be sampler2D, sampler2DArray sampler3D, samplerCube etc.

dtype	Components	Base Format	Internal Format
f1	1	GL_RED	GL_R8
f1	2	GL_RG	GL_RG8
f1	3	GL_RGB	GL_RGB8
f1	4	GL_RGBA	GL_RGBA8

f2 textures stores 16 bit float values (GL_HALF_FLOAT).

dtype	Components	Base Format	Internal Format
f2	1	GL_RED	GL_R16F
f2	2	GL_RG	GL_RG16F
f2	3	GL_RGB	GL_RGB16F
f2	4	GL_RGBA	GL_RGBA16F

f4 textures store 32 bit float values. (GL_FLOAT) Note that some drivers do not like 3 components because of alignment.

dtype	Components	Base Format	Internal Format
f4	1	GL_RED	GL_R32F
f4	2	GL_RG	GL_RG32F
f4	3	GL_RGB	GL_RGB32F
f4	4	GL_RGBA	GL_RGBA32F

Integer Textures#

Integer textures come in a signed and unsigned version. The advantage with integer textures is that shader can read the raw integer values from them using for example usampler* (unsigned) or isampler* (signed).

Integer textures do not support LINEAR filtering (only NEAREST).

Unsigned#

u1 textures store unsigned byte values (GL_UNSIGNED_BYTE).

In shaders the sampler type should be usampler2D, usampler2DArray usampler3D, usamplerCube etc.

dtype	Components	Base Format	Internal Format
u1	1	GL_RED_INTEGER	GL_R8UI
u1	2	GL_RG_INTEGER	GL_RG8UI
u1	3	GL_RGB_INTEGER	GL_RGB8UI
u1	4	GL_RGBA_INTEGER	GL_RGBA8UI

u2 textures store 16 bit unsigned integers (GL_UNSIGNED_SHORT).

dtype	Components	Base Format	Internal Format
u2	1	GL_RED_INTEGER	GL_R16UI
u2	2	GL_RG_INTEGER	GL_RG16UI
u2	3	GL_RGB_INTEGER	GL_RGB16UI
u2	4	GL_RGBA_INTEGER	GL_RGBA16UI

u4 textures store 32 bit unsigned integers (GL_UNSIGNED_INT)

dtype	Components	Base Format	Internal Format
u4	1	GL_RED_INTEGER	GL_R32UI
u4	2	GL_RG_INTEGER	GL_RG32UI
u4	3	GL_RGB_INTEGER	GL_RGB32UI
u4	4	GL_RGBA_INTEGER	GL_RGBA32UI

Signed#

i1 textures store signed byte values (GL_BYTE).

In shaders the sampler type should be isampler2D, isampler2DArray isampler3D, isamplerCube etc.

dtype	Components	Base Format	Internal Format
i1	1	GL_RED_INTEGER	GL_R8I
i1	2	GL_RG_INTEGER	GL_RG8I
i1	3	GL_RGB_INTEGER	GL_RGB8I
i1	4	GL_RGBA_INTEGER	GL_RGBA8I

i2 textures store 16 bit integers (GL_SHORT).

dtype	Components	Base Format	Internal Format
i2	1	GL_RED_INTEGER	GL_R16I
i2	2	GL_RG_INTEGER	GL_RG16I
i2	3	GL_RGB_INTEGER	GL_RGB16I
i2	4	GL_RGBA_INTEGER	GL_RGBA16I

i4 textures store 32 bit integers (GL_INT)

dtype	Components	Base Format	Internal Format
i4	1	GL_RED_INTEGER	GL_R32I
i4	2	GL_RG_INTEGER	GL_RG32I
i4	3	GL_RGB_INTEGER	GL_RGB32I
i4	4	GL_RGBA_INTEGER	GL_RGBA32I

Normalized Integer Textures#

Normalized integers are integer texture, but texel reads in a shader returns normalized values ([0.0, 1.0]). For example an unsigned 16 bit fragment with the value 2**16-1 will be read as 1.0.

Normalized integer textures should use the sampler2D sampler type. Also note that there’s no standard for normalized 32 bit integer textures because a float32 doesn’t have enough precision to express a 32 bit integer as a number between 0.0 and 1.0.

Unsigned#

nu1 textures is really the same as an f1. Each component is a GL_UNSIGNED_BYTE, but are read by the shader in normalized form [0.0, 1.0].

dtype	Components	Base Format	Internal Format
nu1	1	GL_RED	GL_R8
nu1	2	GL_RG	GL_RG8
nu1	3	GL_RGB	GL_RGB8
nu1	4	GL_RGBA	GL_RGBA8

nu2 textures store 16 bit unsigned integers (GL_UNSIGNED_SHORT). The value range [0, 2**16-1] will be normalized into [0.0, 1.0].

dtype	Components	Base Format	Internal Format
nu2	1	GL_RED	GL_R16
nu2	2	GL_RG	GL_RG16
nu2	3	GL_RGB	GL_RGB16
nu2	4	GL_RGBA	GL_RGBA16

Signed#

ni1 textures store 8 bit signed integers (GL_BYTE). The value range [0, 127] will be normalized into [0.0, 1.0]. Negative values will be clamped.

dtype	Components	Base Format	Internal Format
ni1	1	GL_RED	GL_R8
ni1	2	GL_RG	GL_RG8
ni1	3	GL_RGB	GL_RGB8
ni1	4	GL_RGBA	GL_RGBA8

ni2 textures store 16 bit signed integers (GL_SHORT). The value range [0, 2**15-1] will be normalized into [0.0, 1.0]. Negative values will be clamped.

dtype	Components	Base Format	Internal Format
ni2	1	GL_RED	GL_R16
ni2	2	GL_RG	GL_RG16
ni2	3	GL_RGB	GL_RGB16
ni2	4	GL_RGBA	GL_RGBA16

Overriding internalformat#

Context.texture() supports overriding the internalformat of the texture. This is only necessary when needing a different internal formats from the tables above. This can for example be GL_SRGB8 = 0x8C41 or some compressed format. You may also need to look up in Context.extensions to ensure the context supports internalformat you are using. We do not provide the enum values for these alternative internalformats. They can be looked up in the registry : https://raw.githubusercontent.com/KhronosGroup/OpenGL-Registry/master/xml/gl.xml

Example:

texture = ctx.texture(image.size, 3, data=srbg_data, internal_format=GL_SRGB8)

Buffer Format#

Description#

A buffer format is a short string describing the layout of data in a vertex buffer object (VBO).

A VBO often contains a homogeneous array of C-like structures. The buffer format describes what each element of the array looks like. For example, a buffer containing an array of high-precision 2D vertex positions might have the format "2f8" - each element of the array consists of two floats, each float being 8 bytes wide, ie. a double.

Buffer formats are used in the Context.vertex_array() constructor, as the 2nd component of the content arg. See the Example of simple usage below.

Syntax#

A buffer format looks like:

[count]type[size] [[count]type[size]...] [/usage]

Where:

count is an optional integer. If omitted, it defaults to 1.
type is a single character indicating the data type:
- f float
- i int
- u unsigned int
- x padding
size is an optional number of bytes used to store the type. If omitted, it defaults to 4 for numeric types, or to 1 for padding bytes.

A format may contain multiple, space-separated [count]type[size] triples (See the Example of single interleaved array), followed by:
/usage is optional. It should be preceded by a space, and then consists of a slash followed by a single character, indicating how successive values in the buffer should be passed to the shader:
- /v per vertex. Successive values from the buffer are passed to each vertex. This is the default behavior if usage is omitted.
- /i per instance. Successive values from the buffer are passed to each instance.
- /r per render. the first buffer value is passed to every vertex of every instance. ie. behaves like a uniform.
When passing multiple VBOs to a VAO, the first one must be of usage /v, as shown in the Example of multiple arrays with differing /usage.

Valid combinations of type and size are:

	size
type	1	2	4	8
f	Unsigned byte (normalized)	Half float	Float	Double
i	Byte	Short	Int	-
u	Unsigned byte	Unsigned short	Unsigned int	-
x	1 byte	2 bytes	4 bytes	8 bytes

The entry f1 has two unusual properties:

Its type is f (for float), but it defines a buffer containing unsigned bytes. For this size of floats only, the values are normalized, ie. unsigned bytes from 0 to 255 in the buffer are converted to float values from 0.0 to 1.0 by the time they reach the vertex shader. This is intended for passing in colors as unsigned bytes.
Three unsigned bytes, with a format of 3f1, may be assigned to a vec3 attribute, as one would expect. But, from ModernGL v6.0, they can alternatively be passed to a vec4 attribute. This is intended for passing a buffer of 3-byte RGB values into an attribute which also contains an alpha channel.

There are no size 8 variants for types i and u.

This buffer format syntax is specific to ModernGL. As seen in the usage examples below, the formats sometimes look similar to the format strings passed to struct.pack, but that is a different syntax (documented here.)

Buffer formats can represent a wide range of vertex attribute formats. For rare cases of specialized attribute formats that are not expressible using buffer formats, there is a VertexArray.bind() method, to manually configure the underlying OpenGL binding calls. This is not generally recommended.

Examples#

Example buffer formats#

"2f" has a count of 2 and a type of f (float). Hence it describes two floats, passed to a vertex shader’s vec2 attribute. The size of the floats is unspecified, so defaults to 4 bytes. The usage of the buffer is unspecified, so defaults to /v (vertex), meaning each successive pair of floats in the array are passed to successive vertices during the render call.

"3i2/i" means three i (integers). The size of each integer is 2 bytes, ie. they are shorts, passed to an ivec3 attribute. The trailing /i means that consecutive values in the buffer are passed to successive instances during an instanced render call. So the same value is passed to every vertex within a particular instance.

Buffers contining interleaved values are represented by multiple space separated count-type-size triples. Hence:

"2f 3u x /v" means:

2f: two floats, passed to a vec2 attribute, followed by

3u: three unsigned bytes, passed to a uvec3, then

x: a single byte of padding, for alignment.

The /v indicates successive elements in the buffer are passed to successive vertices during the render. This is the default, so the /v could be omitted.

Example of simple usage#

Consider a VBO containing 2D vertex positions, forming a single triangle:

# a 2D triangle (ie. three (x, y) vertices)
verts = [
     0.0, 0.9,
    -0.5, 0.0,
     0.5, 0.0,
]

# pack all six values into a binary array of C-like floats
verts_buffer = struct.pack("6f", *verts)

# put the array into a VBO
vbo = ctx.buffer(verts_buffer)

# use the VBO in a VAO
vao = ctx.vertex_array(
    shader_program,
    [
        (vbo, "2f", "in_vert"), # <---- the "2f" is the buffer format
    ]
    index_buffer_object
)

The line (vbo, "2f", "in_vert"), known as the VAO content, indicates that vbo contains an array of values, each of which consists of two floats. These values are passed to an in_vert attribute, declared in the vertex shader as:

in vec2 in_vert;

The "2f" format omits a size component, so the floats default to 4-bytes each. The format also omits the trailing /usage component, which defaults to /v, so successive (x, y) rows from the buffer are passed to successive vertices during the render call.

Example of single interleaved array#

A buffer array might contain elements consisting of multiple interleaved values.

For example, consider a buffer array, each element of which contains a 2D vertex position as floats, an RGB color as unsigned ints, and a single byte of padding for alignment:

position		color			padding
x	y	r	g	b	-
float	float	unsigned byte	unsigned byte	unsigned byte	byte

Such a buffer, however you choose to construct it, would then be passed into a VAO using:

vao = ctx.vertex_array(
    shader_program,
    [
        (vbo, "2f 3f1 x", "in_vert", "in_color")
    ]
    index_buffer_object
)

The format starts with 2f, for the two position floats, which will be passed to the shader’s in_vert attribute, declared as:

in vec2 in_vert;

Next, after a space, is 3f1, for the three color unsigned bytes, which get normalized to floats by f1. These floats will be passed to the shader’s in_color attribute:

in vec3 in_color;

Finally, the format ends with x, a single byte of padding, which needs no shader attribute name.

Example of multiple arrays with differing `/usage`#

To illustrate the trailing /usage portion, consider rendering a dozen cubes with instanced rendering. We will use:

vbo_verts_normals contains vertices (3 floats) and normals (3 floats) for the vertices within a single cube.
vbo_offset_orientation contains offsets (3 floats) and orientations (9 float matrices) that are used to position and orient each cube.
vbo_colors contains colors (3 floats). In this example, there is only one color in the buffer, that will be used for every vertex of every cube.

Our shader will take all the above values as attributes.

We bind the above VBOs in a single VAO, to prepare for an instanced rendering call:

vao = ctx.vertex_array(
    shader_program,
    [
        (vbo_verts_normals,      "3f 3f /v", "in_vert", "in_norm"),
        (vbo_offset_orientation, "3f 9f /i", "in_offset", "in_orientation"),
        (vbo_colors,             "3f /r",    "in_color"),
    ]
    index_buffer_object
)

So, the vertices and normals, using /v, are passed to each vertex within an instance. This fulfills the rule that the first VBO in a VAO must have usage /v. These are passed to vertex attributes as:

in vec3 in_vert;
in vec3 in_norm;

The offsets and orientations pass the same value to each vertex within an instance, but then pass the next value in the buffer to the vertices of the next instance. Passed as:

in vec3 in_offset;
in mat3 in_orientation;

The single color is passed to every vertex of every instance. If we had stored the color with /v or /i, then we would have had to store duplicate identical color values in vbo_colors - one per instance or one per vertex. To render all our cubes in a single color, this is needless duplication. Using /r, only one color is require the buffer, and it is passed to every vertex of every instance for the whole render call:

in vec3 in_color;

An alternative approach would be to pass in the color as a uniform, since it is constant. But doing it as an attribute is more flexible. It allows us to reuse the same shader program, bound to a different buffer, to pass in color data which varies per instance, or per vertex.

Techniques#

Headless on Ubuntu 18 Server#

Dependencies#

Headless rendering can be achieved with EGL or X11. We’ll cover both cases.

Starting with fresh ubuntu 18 server install we need to install required packages:

sudo apt-install python3-pip mesa-utils libegl1-mesa xvfb

This should install mesa an diagnostic tools if needed later.

mesa-utils installs libgl1-mesa and tools like glxinfo`
libegl1-mesa is optional if using EGL instead of X11

Creating a context#

The libraries we are going to interact with has the following locations:

/usr/lib/x86_64-linux-gnu/libGL.so.1
/usr/lib/x86_64-linux-gnu/libX11.so.6
/usr/lib/x86_64-linux-gnu/libEGL.so.1

Double check that you have these libraries installed. ModernGL through the glcontext library will use ctype.find_library to locate the latest installed version.

Before we can create a context we to run a virtual display:

export DISPLAY=:99.0
Xvfb :99 -screen 0 640x480x24 &

Now we can create a context with x11 or egl:

# X11
import moderngl
ctx = moderngl.create_context(
    standalone=True,
    # These are OPTIONAL if you want to load a specific version
    libgl='libGL.so.1',
    libx11='libX11.so.6',
)

# EGL
import moderngl
ctx = moderngl.create_context(
    standalone=True,
    backend='egl',
    # These are OPTIONAL if you want to load a specific version
    libgl='libGL.so.1',
    libegl='libEGL.so.1',
)

Running an example#

Checking that everything works can be done with a basic triangle example.

Install dependencies:

pip3 install moderngl numpy pyrr pillow

The following example renders a triangle and writes it to a png file so we can verify the contents.

import moderngl
import numpy as np
from PIL import Image
from pyrr import Matrix44

# -------------------
# CREATE CONTEXT HERE
# -------------------

prog = ctx.program(vertex_shader="""
    #version 330
    uniform mat4 model;
    in vec2 in_vert;
    in vec3 in_color;
    out vec3 color;
    void main() {
        gl_Position = model * vec4(in_vert, 0.0, 1.0);
        color = in_color;
    }
    """,
    fragment_shader="""
    #version 330
    in vec3 color;
    out vec4 fragColor;
    void main() {
        fragColor = vec4(color, 1.0);
    }
""")

vertices = np.array([
    -0.6, -0.6,
    1.0, 0.0, 0.0,
    0.6, -0.6,
    0.0, 1.0, 0.0,
    0.0, 0.6,
    0.0, 0.0, 1.0,
], dtype='f4')

vbo = ctx.buffer(vertices)
vao = ctx.simple_vertex_array(prog, vbo, 'in_vert', 'in_color')
fbo = ctx.framebuffer(color_attachments=[ctx.texture((512, 512), 4)])

fbo.use()
ctx.clear()
prog['model'].write(Matrix44.from_eulers((0.0, 0.1, 0.0), dtype='f4'))
vao.render(moderngl.TRIANGLES)

data = fbo.read(components=3)
image = Image.frombytes('RGB', fbo.size, data)
image = image.transpose(Image.FLIP_TOP_BOTTOM)
image.save('output.png')

Reference#

moderngl#

Attributes#

Attributes available in the root moderngl module. Some may be listed in their original sub-module, but they are imported during initialization.

Context Flags#

Also available in the Context instance including mode details.

moderngl.NOTHING: moderngl.Constant#: Represents no states. Can be used with Context.enable_only() to disable all states.

moderngl.BLEND: moderngl.Constant#: Enable/disable blending

moderngl.DEPTH_TEST: moderngl.Constant#: Enable/disable depth testing

moderngl.CULL_FACE: moderngl.Constant#: Enable/disable face culling

moderngl.RASTERIZER_DISCARD: moderngl.Constant#: Enable/disable rasterization

moderngl.PROGRAM_POINT_SIZE: moderngl.Constant#

Enables gl_PointSize in vertex or geometry shaders.

When enabled we can write to gl_PointSize in the vertex shader to specify the point size for each individual point.

If this value is not set in the shader the behavior is undefined. This means the points may or may not appear depending if the drivers enforce some default value for gl_PointSize.

When disabled Context.point_size is used.

Type: Context flag

Primitive Modes#

Also available in the Context instance including mode details.

moderngl.POINTS: moderngl.Constant#: Each vertex represents a point

moderngl.LINES: moderngl.Constant#: Vertices 0 and 1 are considered a line. Vertices 2 and 3 are considered a line. And so on. If the user specifies a non-even number of vertices, then the extra vertex is ignored.

moderngl.LINE_LOOP: moderngl.Constant#: As line strips, except that the first and last vertices are also used as a line. Thus, you get n lines for n input vertices. If the user only specifies 1 vertex, the drawing command is ignored. The line between the first and last vertices happens after all of the previous lines in the sequence.

moderngl.LINE_STRIP: moderngl.Constant#: The adjacent vertices are considered lines. Thus, if you pass n vertices, you will get n-1 lines. If the user only specifies 1 vertex, the drawing command is ignored.

moderngl.TRIANGLES: moderngl.Constant#: Vertices 0, 1, and 2 form a triangle. Vertices 3, 4, and 5 form a triangle. And so on.

moderngl.TRIANGLE_STRIP: moderngl.Constant#: Every group of 3 adjacent vertices forms a triangle. The face direction of the strip is determined by the winding of the first triangle. Each successive triangle will have its effective face order reversed, so the system compensates for that by testing it in the opposite way. A vertex stream of n length will generate n-2 triangles.

moderngl.TRIANGLE_FAN: moderngl.Constant#: The first vertex is always held fixed. From there on, every group of 2 adjacent vertices form a triangle with the first. So with a vertex stream, you get a list of triangles like so: (0, 1, 2) (0, 2, 3), (0, 3, 4), etc. A vertex stream of n length will generate n-2 triangles.

moderngl.LINES_ADJACENCY: moderngl.Constant#: These are special primitives that are expected to be used specifically with geomtry shaders. These primitives give the geometry shader more vertices to work with for each input primitive. Data needs to be duplicated in buffers.

moderngl.LINE_STRIP_ADJACENCY: moderngl.Constant#: These are special primitives that are expected to be used specifically with geomtry shaders. These primitives give the geometry shader more vertices to work with for each input primitive. Data needs to be duplicated in buffers.

moderngl.TRIANGLES_ADJACENCY: moderngl.Constant#: These are special primitives that are expected to be used specifically with geomtry shaders. These primitives give the geometry shader more vertices to work with for each input primitive. Data needs to be duplicated in buffers.

moderngl.TRIANGLE_STRIP_ADJACENCY: moderngl.Constant#: These are special primitives that are expected to be used specifically with geomtry shaders. These primitives give the geometry shader more vertices to work with for each input primitive. Data needs to be duplicated in buffers.

moderngl.PATCHES: moderngl.Constant#: primitive type can only be used when Tessellation is active. It is a primitive with a user-defined number of vertices, which is then tessellated based on the control and evaluation shaders into regular points, lines, or triangles, depending on the TES’s settings.

Texture Filters#

Also available in the Context instance including mode details.

moderngl.NEAREST: moderngl.Constant#: Returns the value of the texture element that is nearest (in Manhattan distance) to the specified texture coordinates.

moderngl.LINEAR: moderngl.Constant#: Returns the weighted average of the four texture elements that are closest to the specified texture coordinates. These can include items wrapped or repeated from other parts of a texture, depending on the values of texture repeat mode, and on the exact mapping.

moderngl.NEAREST_MIPMAP_NEAREST: moderngl.Constant#: Chooses the mipmap that most closely matches the size of the pixel being textured and uses the NEAREST` criterion (the texture element closest to the specified texture coordinates) to produce a texture value.

moderngl.LINEAR_MIPMAP_NEAREST: moderngl.Constant#: Chooses the mipmap that most closely matches the size of the pixel being textured and uses the LINEAR criterion (a weighted average of the four texture elements that are closest to the specified texture coordinates) to produce a texture value.

moderngl.NEAREST_MIPMAP_LINEAR: moderngl.Constant#: Chooses the two mipmaps that most closely match the size of the pixel being textured and uses the NEAREST criterion (the texture element closest to the specified texture coordinates ) to produce a texture value from each mipmap. The final texture value is a weighted average of those two values.

moderngl.LINEAR_MIPMAP_LINEAR: moderngl.Constant#: Chooses the two mipmaps that most closely match the size of the pixel being textured and uses the LINEAR criterion (a weighted average of the texture elements that are closest to the specified texture coordinates) to produce a texture value from each mipmap. The final texture value is a weighted average of those two values.

Blend Functions#

Also available in the Context instance including mode details.

moderngl.ZERO: moderngl.Constant#: (0,0,0,0)

moderngl.ONE: moderngl.Constant#: (1,1,1,1)

moderngl.SRC_COLOR: moderngl.Constant#: (Rs0/kR,Gs0/kG,Bs0/kB,As0/kA)

moderngl.ONE_MINUS_SRC_COLOR: moderngl.Constant#: (1,1,1,1) - (Rs0/kR,Gs0/kG,Bs0/kB,As0/kA)

moderngl.SRC_ALPHA: moderngl.Constant#: (As0/kA,As0/kA,As0/kA,As0/kA)

moderngl.ONE_MINUS_SRC_ALPHA: moderngl.Constant#: (1,1,1,1) - (As0/kA,As0/kA,As0/kA,As0/kA)

moderngl.DST_ALPHA: moderngl.Constant#: (Ad/kA,Ad/kA,Ad/kA,Ad/kA)

moderngl.ONE_MINUS_DST_ALPHA: moderngl.Constant#: (1,1,1,1) - (Ad/kA,Ad/kA,Ad/kA,Ad/kA)

moderngl.DST_COLOR: moderngl.Constant#: (Rd/kR,Gd/kG,Bd/kB,Ad/kA)

moderngl.ONE_MINUS_DST_COLOR: moderngl.Constant#: (1,1,1,1) - (Rd/kR,Gd/kG,Bd/kB,Ad/kA)

Shortcuts#

moderngl.DEFAULT_BLENDING: moderngl.Constant#: Shotcut for the default blending SRC_ALPHA, ONE_MINUS_SRC_ALPHA

moderngl.ADDITIVE_BLENDING: moderngl.Constant#: Shotcut for additive blending ONE, ONE

moderngl.PREMULTIPLIED_ALPHA: moderngl.Constant#: Shotcut for blend mode when using premultiplied alpha SRC_ALPHA, ONE

Blend Equations#

Also available in the Context instance including mode details.

moderngl.FUNC_ADD: moderngl.Constant#: source + destination

moderngl.FUNC_SUBTRACT: moderngl.Constant#: source - destination

moderngl.FUNC_REVERSE_SUBTRACT: moderngl.Constant#: destination - source

moderngl.MIN: moderngl.Constant#: Minimum of source and destination

moderngl.MAX: moderngl.Constant#: Maximum of source and destination

Provoking Vertex#

Also available in the Context instance including mode details.

moderngl.FIRST_VERTEX_CONVENTION: moderngl.Constant#: Specifies the first vertex should be used as the source of data for flat shaded varyings. Used with Context.provoking_vertex.

moderngl.LAST_VERTEX_CONVENTION: moderngl.Constant#: Specifies the last vertex should be used as the source of data for flat shaded varyings. Used with Context.provoking_vertex.

Functions#

Also see Context.

moderngl.create_context(require: Optional[int] = None, standalone: bool = False, share: bool = False, **settings: Dict[str, Any]) → moderngl.Context

Create a ModernGL context by loading OpenGL functions from an existing OpenGL context. An OpenGL context must exists.

Example:

# Accept the current context version
ctx = moderngl.create_context()

# Require at least OpenGL 4.3
ctx = moderngl.create_context(require=430)

# Create a headless context requiring OpenGL 4.3
ctx = moderngl.create_context(require=430, standalone=True)

Keyword Arguments

require (int) – OpenGL version code (default: 330)
standalone (bool) – Headless flag
share (bool) – Attempt to create a shared context
**settings – Other backend specific settings

Returns

Context object

moderngl.create_standalone_context(require: Optional[int] = None, share: bool = False, **settings: Dict[str, Any]) → moderngl.Context

Create a standalone/headless ModernGL context.

The preferred way of making a context is through moderngl.create_context().

Example:

# Create a context with highest possible supported version
ctx = moderngl.create_context()

# Require at least OpenGL 4.3
ctx = moderngl.create_context(require=430)

Keyword Arguments

require (int) – OpenGL version code.
share (bool) – Attempt to create a shared context
settings – keyword config values for the context backend

Returns

Context object

moderngl.detect_format(program: moderngl.Program, attributes: Any, mode: str = 'mgl') → str

Detect format for vertex attributes.

The format returned does not contain padding.

Parameters

program (Program) – The program.
attributes (list) – A list of attribute names.

Returns

str

Context#

class moderngl.Context#

Class exposing OpenGL features.

ModernGL objects can be created from this class.

Create#

moderngl.create_context(require: Optional[int] = None, standalone: bool = False, share: bool = False, **settings: Dict[str, Any]) → moderngl.Context#

Create a ModernGL context by loading OpenGL functions from an existing OpenGL context. An OpenGL context must exists.

Example:

# Accept the current context version
ctx = moderngl.create_context()

# Require at least OpenGL 4.3
ctx = moderngl.create_context(require=430)

# Create a headless context requiring OpenGL 4.3
ctx = moderngl.create_context(require=430, standalone=True)

Keyword Arguments

require (int) – OpenGL version code (default: 330)
standalone (bool) – Headless flag
share (bool) – Attempt to create a shared context
**settings – Other backend specific settings

Returns

Context object

moderngl.create_standalone_context(require: Optional[int] = None, share: bool = False, **settings: Dict[str, Any]) → moderngl.Context#

Create a standalone/headless ModernGL context.

The preferred way of making a context is through moderngl.create_context().

Example:

# Create a context with highest possible supported version
ctx = moderngl.create_context()

# Require at least OpenGL 4.3
ctx = moderngl.create_context(require=430)

Keyword Arguments

require (int) – OpenGL version code.
share (bool) – Attempt to create a shared context
settings – keyword config values for the context backend

Returns

Context object

ModernGL Objects#

Context.program(*, vertex_shader: str, fragment_shader: Optional[str] = None, geometry_shader: Optional[str] = None, tess_control_shader: Optional[str] = None, tess_evaluation_shader: Optional[str] = None, varyings: Tuple[str, ...] = (), fragment_outputs: Optional[Dict[str, int]] = None, varyings_capture_mode: str = 'interleaved') → moderngl.Program#

Create a Program object.

The varyings are only used when a transform program is created to specify the names of the output varyings to capture in the output buffer.

fragment_outputs can be used to programmatically map named fragment shader outputs to a framebuffer attachment numbers. This can also be done by using layout(location=N) in the fragment shader.

Parameters

vertex_shader (str) – The vertex shader source.
fragment_shader (str) – The fragment shader source.
geometry_shader (str) – The geometry shader source.
tess_control_shader (str) – The tessellation control shader source.
tess_evaluation_shader (str) – The tessellation evaluation shader source.
varyings (list) – A list of varyings.
fragment_outputs (dict) – A dictionary of fragment outputs.

Returns

Program object

Context.simple_vertex_array(program: moderngl.Program, buffer: moderngl.Buffer, *attributes: Union[List[str], Tuple[str, ...]], index_buffer: Optional[moderngl.Buffer] = None, index_element_size: int = 4, mode: Optional[int] = None) → moderngl.VertexArray#

Create a VertexArray object.

Warning

This method is deprecated and may be removed in the future. Use Context.vertex_array() instead. It also supports the argument format this method describes.

Parameters

program (Program) – The program used when rendering.
buffer (Buffer) – The buffer.
attributes (list) – A list of attribute names.

Keyword Arguments

index_element_size (int) – byte size of each index element, 1, 2 or 4.
index_buffer (Buffer) – An index buffer.
mode (int) – The default draw mode (for example: TRIANGLES)

Returns

VertexArray object

Context.vertex_array(*args, **kwargs) → moderngl.VertexArray#

Create a VertexArray object.

The vertex array describes how buffers are read by a shader program. We need to supply buffer formats and attributes names. The attribute names are defined by the user in the glsl code and can be anything.

Examples:

# Empty vertext array (no attribute input)
vao = ctx.vertex_array(program)

# Simple version with a single buffer
vao = ctx.vertex_array(program, buffer, 'in_position', 'in_normal')
vao = ctx.vertex_array(program, buffer, 'in_position', 'in_normal', index_buffer=ibo)

# Multiple buffers
vao = ctx.vertex_array(program, [
    (buffer1, '3f', 'in_position'),
    (buffer2, '3f', 'in_normal'),
])
vao = ctx.vertex_array(program, [
        (buffer1, '3f', 'in_position'),
        (buffer2, '3f', 'in_normal'),
    ],
    index_buffer=ibo,
    index_element_size=2,  # 16 bit / 'u2' index buffer
)

This method also supports arguments for Context.simple_vertex_array().

Parameters

program (Program) – The program used when rendering
content (list) – A list of (buffer, format, attributes). See Buffer Format.

Keyword Arguments

index_buffer (Buffer) – An index buffer (optional)
index_element_size (int) – byte size of each index element, 1, 2 or 4.
skip_errors (bool) – Ignore errors during creation
mode (int) – The default draw mode (for example: TRIANGLES)

Returns

VertexArray object

Context.buffer(data: Optional[Any] = None, *, reserve: int = 0, dynamic: bool = False) → moderngl.Buffer#

Create a Buffer object.

Parameters

data (bytes) – Content of the new buffer.

Keyword Arguments

reserve (int) – The number of bytes to reserve.
dynamic (bool) – Treat buffer as dynamic.

Returns

Buffer object

Context.texture(size: Tuple[int, int], components: int, data: Optional[Any] = None, *, samples: int = 0, alignment: int = 1, dtype: str = 'f1', internal_format: Optional[int] = None) → moderngl.Texture#

Create a Texture object.

Warning

Do not play with internal_format unless you know exactly you are doing. This is an override to support sRGB and compressed textures if needed.

Parameters

size (tuple) – The width and height of the texture.
components (int) – The number of components 1, 2, 3 or 4.
data (bytes) – Content of the texture.

Keyword Arguments

samples (int) – The number of samples. Value 0 means no multisample format.
alignment (int) – The byte alignment 1, 2, 4 or 8.
dtype (str) – Data type.
internal_format (int) – Override the internalformat of the texture (IF needed)

Returns

Texture object

Context.depth_texture(size: Tuple[int, int], data: Optional[Any] = None, *, samples: int = 0, alignment: int = 4) → moderngl.Texture#

Create a Texture object.

Parameters

size (tuple) – The width and height of the texture.
data (bytes) – Content of the texture.

Keyword Arguments

samples (int) – The number of samples. Value 0 means no multisample format.
alignment (int) – The byte alignment 1, 2, 4 or 8.

Returns

Texture object

Context.texture3d(size: Tuple[int, int, int], components: int, data: Optional[Any] = None, *, alignment: int = 1, dtype: str = 'f1') → moderngl.Texture3D#

Create a Texture3D object.

Parameters

size (tuple) – The width, height and depth of the texture.
components (int) – The number of components 1, 2, 3 or 4.
data (bytes) – Content of the texture.

Keyword Arguments

alignment (int) – The byte alignment 1, 2, 4 or 8.
dtype (str) – Data type.

Returns

Texture3D object

Context.texture_array(size: Tuple[int, int, int], components: int, data: Optional[Any] = None, *, alignment: int = 1, dtype: str = 'f1') → moderngl.TextureArray#

Create a TextureArray object.

Parameters

size (tuple) – The (width, height, layers) of the texture.
components (int) – The number of components 1, 2, 3 or 4.
data (bytes) – Content of the texture. The size must be (width, height * layers) so each layer is stacked vertically.

Keyword Arguments

alignment (int) – The byte alignment 1, 2, 4 or 8.
dtype (str) – Data type.

Returns

Texture3D object

Context.texture_cube(size: Tuple[int, int], components: int, data: Optional[Any] = None, *, alignment: int = 1, dtype: str = 'f1', internal_format: Optional[int] = None) → moderngl.TextureCube#

Create a TextureCube object.

Note that the width and height of the cubemap must be the same unless you are using a non-standard extension.

Parameters

size (tuple) – The width, height of the texture. Each side of the cube will have this size.
components (int) – The number of components 1, 2, 3 or 4.
data (bytes) – Content of the texture. The data should be have the following ordering: positive_x, negative_x, positive_y, negative_y, positive_z, negative_z

Keyword Arguments

alignment (int) – The byte alignment 1, 2, 4 or 8.
dtype (str) – Data type.
internal_format (int) – Override the internalformat of the texture (IF needed)

Returns

TextureCube object

Context.external_texture(glo: int, size: Tuple[int, int], components: int, samples: int, dtype: str) → moderngl.Texture#

Create a Texture object from an existing OpenGL texture object.

Parameters

glo (int) – External OpenGL texture object.
size (tuple) – The width and height of the texture.
components (int) – The number of components 1, 2, 3 or 4.
samples (int) – The number of samples. Value 0 means no multisample format.
dtype (str) – Data type.

Context.simple_framebuffer(size: Tuple[int, int], components: int = 4, *, samples: int = 0, dtype: str = 'f1') → moderngl.Framebuffer#

Creates a Framebuffer with a single color attachment and depth buffer using moderngl.Renderbuffer attachments.

Parameters

size (tuple) – The width and height of the renderbuffer.
components (int) – The number of components 1, 2, 3 or 4.

Keyword Arguments

samples (int) – The number of samples. Value 0 means no multisample format.
dtype (str) – Data type.

Returns

Framebuffer object

Context.framebuffer(color_attachments: Any = (), depth_attachment: Optional[Union[moderngl.Texture, moderngl.Renderbuffer]] = None) → moderngl.Framebuffer#

A Framebuffer is a collection of buffers that can be used as the destination for rendering. The buffers for Framebuffer objects reference images from either Textures or Renderbuffers.

Parameters

color_attachments (list) – A list of Texture or Renderbuffer objects.
depth_attachment (Renderbuffer or Texture) – The depth attachment.

Returns

Framebuffer object

Context.renderbuffer(size: Tuple[int, int], components: int = 4, *, samples: int = 0, dtype: str = 'f1') → moderngl.Renderbuffer#

Renderbuffer objects are OpenGL objects that contain images. They are created and used specifically with Framebuffer objects.

Parameters

size (tuple) – The width and height of the renderbuffer.
components (int) – The number of components 1, 2, 3 or 4.

Keyword Arguments

samples (int) – The number of samples. Value 0 means no multisample format.
dtype (str) – Data type.

Returns

Renderbuffer object

Context.depth_renderbuffer(size: Tuple[int, int], *, samples: int = 0) → moderngl.Renderbuffer#

Renderbuffer objects are OpenGL objects that contain images. They are created and used specifically with Framebuffer objects.

Parameters: size (tuple) – The width and height of the renderbuffer.
Keyword Arguments: samples (int) – The number of samples. Value 0 means no multisample format.
Returns: Renderbuffer object

Context.scope(framebuffer: Optional[moderngl.Framebuffer] = None, enable_only: Optional[int] = None, *, textures: Tuple[Tuple[moderngl.Texture, int], ...] = (), uniform_buffers: Tuple[Tuple[moderngl.Buffer, int], ...] = (), storage_buffers: Tuple[Tuple[moderngl.Buffer, int], ...] = (), samplers: Tuple[Tuple[moderngl.Sampler, int], ...] = (), enable: Optional[int] = None) → moderngl.Scope#

Create a Scope object.

Parameters

framebuffer (Framebuffer) – The framebuffer to use when entering.
enable_only (int) – The enable_only flags to set when entering.

Keyword Arguments

textures (tuple) – List of (texture, binding) tuples.
uniform_buffers (tuple) – Tuple of (buffer, binding) tuples.
storage_buffers (tuple) – Tuple of (buffer, binding) tuples.
samplers (tuple) – Tuple of sampler bindings
enable (int) – Flags to enable for this vao such as depth testing and blending

Context.query(*, samples: bool = False, any_samples: bool = False, time: bool = False, primitives: bool = False) → moderngl.Query#

Create a Query object.

Keyword Arguments

samples (bool) – Query GL_SAMPLES_PASSED or not.
any_samples (bool) – Query GL_ANY_SAMPLES_PASSED or not.
time (bool) – Query GL_TIME_ELAPSED or not.
primitives (bool) – Query GL_PRIMITIVES_GENERATED or not.

Context.compute_shader(source: str) → moderngl.ComputeShader#

A ComputeShader is a Shader Stage that is used entirely for computing arbitrary information. While it can do rendering, it is generally used for tasks not directly related to drawing.

Parameters: source (str) – The source of the compute shader.
Returns: ComputeShader object

Context.sampler(repeat_x: bool = True, repeat_y: bool = True, repeat_z: bool = True, filter: Optional[Tuple[int, int]] = None, anisotropy: float = 1.0, compare_func: str = '?', border_color: Optional[Tuple[float, float, float, float]] = None, min_lod: float = - 1000.0, max_lod: float = 1000.0, texture: Optional[moderngl.Texture] = None) → moderngl.Sampler#

Create a Sampler object.

Keyword Arguments

repeat_x (bool) – Repeat texture on x
repeat_y (bool) – Repeat texture on y
repeat_z (bool) – Repeat texture on z
filter (tuple) – The min and max filter
anisotropy (float) – Number of samples for anisotropic filtering. Any value greater than 1.0 counts as a use of anisotropic filtering
compare_func – Compare function for depth textures
border_color (tuple) – The (r, g, b, a) color for the texture border. When this value is set the repeat_ values are overridden setting the texture wrap to return the border color when outside [0, 1] range.
min_lod (float) – Minimum level-of-detail parameter (Default -1000.0). This floating-point value limits the selection of highest resolution mipmap (lowest mipmap level)
max_lod (float) – Minimum level-of-detail parameter (Default 1000.0). This floating-point value limits the selection of the lowest resolution mipmap (highest mipmap level)
texture (Texture) – The texture for this sampler

Context.clear_samplers(start: int = 0, end: int = - 1) → None#

Unbinds samplers from texture units.

Sampler bindings do clear automatically between every frame, but lingering samplers can still be a source of weird bugs during the frame rendering. This methods provides a fairly brute force and efficient way to ensure texture units are clear.

Keyword Arguments

start (int) – The texture unit index to start the clearing samplers
stop (int) – The texture unit index to stop clearing samplers

Example:

# Clear texture unit 0, 1, 2, 3, 4
ctx.clear_samplers(start=0, end=5)

# Clear texture unit 4, 5, 6, 7
ctx.clear_samplers(start=4, end=8)

Context.release() → None#

Release the ModernGL context.

If the context is not standalone the standard backends in glcontext will not do anything because the context was not created by moderngl.

Standalone contexts can normally be released.

Methods#

Context.clear(red: float = 0.0, green: float = 0.0, blue: float = 0.0, alpha: float = 0.0, depth: float = 1.0, *, viewport: Optional[Union[Tuple[int, int], Tuple[int, int, int, int]]] = None, color: Optional[Tuple[float, float, float, float]] = None) → None#

Clear the bound framebuffer.

If a viewport passed in, a scissor test will be used to clear the given viewport. This viewport take prescense over the framebuffers scissor. Clearing can still be done with scissor if no viewport is passed in.

This method also respects the color_mask and depth_mask. It can for example be used to only clear the depth or color buffer or specific components in the color buffer.

If the viewport is a 2-tuple it will clear the (0, 0, width, height) where (width, height) is the 2-tuple.

If the viewport is a 4-tuple it will clear the given viewport.

Parameters

red (float) – color component.
green (float) – color component.
blue (float) – color component.
alpha (float) – alpha component.
depth (float) – depth value.

Keyword Arguments

viewport (tuple) – The viewport.
color (tuple) – Optional rgba color tuple

Context.enable_only(flags: int) → None#

Clears all existing flags applying new ones.

Note that the enum values defined in moderngl are not the same as the ones in opengl. These are defined as bit flags so we can logical or them together.

Available flags:

Examples:

# Disable all flags
ctx.enable_only(moderngl.NOTHING)

# Ensure only depth testing and face culling is enabled
ctx.enable_only(moderngl.DEPTH_TEST | moderngl.CULL_FACE)

Parameters: flags (EnableFlag) – The flags to enable

Context.enable(flags: int) → None#

Enable flags.

Note that the enum values defined in moderngl are not the same as the ones in opengl. These are defined as bit flags so we can logical or them together.

For valid flags, please see enable_only().

Examples:

# Enable a single flag
ctx.enable(moderngl.DEPTH_TEST)

# Enable multiple flags
ctx.enable(moderngl.DEPTH_TEST | moderngl.CULL_FACE | moderngl.BLEND)

Parameters: flag (int) – The flags to enable.

Context.disable(flags: int) → None#

Disable flags.

For valid flags, please see enable_only().

Examples:

# Only disable depth testing
ctx.disable(moderngl.DEPTH_TEST)

# Disable depth testing and face culling
ctx.disable(moderngl.DEPTH_TEST | moderngl.CULL_FACE)

Parameters: flag (int) – The flags to disable.

Context.enable_direct(enum: int) → None#

Gives direct access to glEnable so unsupported capabilities in ModernGL can be enabled.

Do not use this to set already supported context flags.

Example:

# Enum value from the opengl registry
GL_CONSERVATIVE_RASTERIZATION_NV = 0x9346
ctx.enable_direct(GL_CONSERVATIVE_RASTERIZATION_NV)

Context.disable_direct(enum: int) → None#

Gives direct access to glDisable so unsupported capabilities in ModernGL can be disabled.

Do not use this to set already supported context flags.

Example:

# Enum value from the opengl registry
GL_CONSERVATIVE_RASTERIZATION_NV = 0x9346
ctx.disable_direct(GL_CONSERVATIVE_RASTERIZATION_NV)

Context.finish() → None#: Wait for all drawing commands to finish.

Context.copy_buffer(dst: moderngl.Buffer, src: moderngl.Buffer, size: int = - 1, *, read_offset: int = 0, write_offset: int = 0) → None#

Copy buffer content.

Parameters

dst (Buffer) – The destination buffer.
src (Buffer) – The source buffer.
size (int) – The number of bytes to copy.

Keyword Arguments

read_offset (int) – The read offset.
write_offset (int) – The write offset.

Context.copy_framebuffer(dst: Union[moderngl.Framebuffer, moderngl.Texture], src: moderngl.Framebuffer) → None#

Copy framebuffer content.

Use this method to:

blit framebuffers.

copy framebuffer content into a texture.

downsample framebuffers. (it will allow to read the framebuffer’s content)

downsample a framebuffer directly to a texture.

Parameters

dst (Framebuffer or Texture) – Destination framebuffer or texture.
src (Framebuffer) – Source framebuffer.

Context.detect_framebuffer(glo: Optional[int] = None) → moderngl.Framebuffer#

Detect a framebuffer.

This is already done when creating a context, but if the underlying window library for some changes the default framebuffer during the lifetime of the application this might be necessary.

Parameters: glo (int) – Framebuffer object.
Returns: Framebuffer object

Context.gc() → int#

Deletes OpenGL objects.

This method must be called to garbage collect OpenGL resources when gc_mode is 'context_gc'`.

Calling this method with any other gc_mode configuration has no effect and is perfectly safe.

Returns: Number of objects deleted
Return type: int

Context.__enter__()#

Enters the context.

This should ideally be used with the with statement:

with other_context as ctx:
    # Do something in this context

When exiting the context the previously bound context is activated again.

Warning

Context switching can be risky unless you know what you are doing. Use with care.

Context.__exit__(exc_type, exc_val, exc_tb)#

Exit the context.

See Context.__enter__()

Attributes#

Context.gc_mode: str#

The garbage collection mode.

The default mode is None meaning no automatic garbage collection is done. Other modes are auto and context_gc. Please see documentation for the appropriate configuration.

Examples:

# Disable automatic garbage collection.
# Each objects needs to be explicitly released.
ctx.gc_mode = None

# Collect all dead objects in the context and
# release them by calling Context.gc()
ctx.gc_mode = 'context_gc'
ctx.gc()  # Deletes the collected objects

# Enable automatic garbage collection like
# we normally expect in python.
ctx.gc_mode = 'auto'

Type: Optional[str]

Context.objects: Deque[Any]#

Moderngl objects scheduled for deletion.

These are deleted when calling Context.gc().

Context.line_width: float#

Set the default line width.

Warning

A line width other than 1.0 is not guaranteed to work across different OpenGL implementations. For wide lines you should be using geometry shaders.

Type: float

Context.point_size: float#

Set/get the point size.

Point size changes the pixel size of rendered points. The min and max values are limited by POINT_SIZE_RANGE. This value usually at least (1, 100), but this depends on the drivers/vendors.

If variable point size is needed you can enable PROGRAM_POINT_SIZE and write to gl_PointSize in the vertex or geometry shader.

Note

Using a geometry shader to create triangle strips from points is often a safer way to render large points since you don’t have have any size restrictions.

Type: float

Context.depth_func: str#

Set the default depth func.

Example:

ctx.depth_func = '<='  # GL_LEQUAL
ctx.depth_func = '<'   # GL_LESS
ctx.depth_func = '>='  # GL_GEQUAL
ctx.depth_func = '>'   # GL_GREATER
ctx.depth_func = '=='  # GL_EQUAL
ctx.depth_func = '!='  # GL_NOTEQUAL
ctx.depth_func = '0'   # GL_NEVER
ctx.depth_func = '1'   # GL_ALWAYS

Type: str

Context.blend_func: Tuple[int, int]#

Set the blend func (write only).

Blend func can be set for rgb and alpha separately if needed.

Supported blend functions are:

moderngl.ZERO
moderngl.ONE
moderngl.SRC_COLOR
moderngl.ONE_MINUS_SRC_COLOR
moderngl.DST_COLOR
moderngl.ONE_MINUS_DST_COLOR
moderngl.SRC_ALPHA
moderngl.ONE_MINUS_SRC_ALPHA
moderngl.DST_ALPHA
moderngl.ONE_MINUS_DST_ALPHA

# Shortcuts
moderngl.DEFAULT_BLENDING     # (SRC_ALPHA, ONE_MINUS_SRC_ALPHA)
moderngl.ADDITIVE_BLENDING    # (ONE, ONE)
moderngl.PREMULTIPLIED_ALPHA  # (SRC_ALPHA, ONE)

Example:

# For both rgb and alpha
ctx.blend_func = moderngl.SRC_ALPHA, moderngl.ONE_MINUS_SRC_ALPHA

# Separate for rgb and alpha
ctx.blend_func = (
    moderngl.SRC_ALPHA, moderngl.ONE_MINUS_SRC_ALPHA,
    moderngl.ONE, moderngl.ONE
)

Type: tuple

Context.blend_equation: Tuple[int, int]#

Set the blend equation (write only).

Blend equations specify how source and destination colors are combined in blending operations. By default FUNC_ADD is used.

Blend equation can be set for rgb and alpha separately if needed.

Supported functions are:

moderngl.FUNC_ADD               # source + destination
moderngl.FUNC_SUBTRACT          # source - destination
moderngl.FUNC_REVERSE_SUBTRACT  # destination - source
moderngl.MIN                    # Minimum of source and destination
moderngl.MAX                    # Maximum of source and destination

Example:

# For both rgb and alpha channel
ctx.blend_equation = moderngl.FUNC_ADD

# Separate for rgb and alpha channel
ctx.blend_equation = moderngl.FUNC_ADD, moderngl.MAX

Type: tuple

Context.viewport: Tuple[int, int, int, int]#

Get or set the viewport of the active framebuffer.

Example:

>>> ctx.viewport
(0, 0, 1280, 720)
>>> ctx.viewport = (0, 0, 640, 360)
>>> ctx.viewport
(0, 0, 640, 360)

If no framebuffer is bound (0, 0, 0, 0) will be returned.

Type: tuple

Context.scissor: Optional[Tuple[int, int, int, int]]#

Get or set the scissor box for the active framebuffer.

When scissor testing is enabled fragments outside the defined scissor box will be discarded. This applies to rendered geometry or Context.clear().

Setting is value enables scissor testing in the framebuffer. Setting the scissor to None disables scissor testing and reverts the scissor box to match the framebuffer size.

Example:

# Enable scissor testing
>>> ctx.scissor = 100, 100, 200, 100
# Disable scissor testing
>>> ctx.scissor = None

If no framebuffer is bound (0, 0, 0, 0) will be returned.

Type: tuple

Context.version_code: int#

The OpenGL version code. Reports 410 for OpenGL 4.1

Type: int

Context.screen: moderngl.Framebuffer#

A Framebuffer instance representing the screen.

Normally set when creating a context with create_context() attaching to an existing context. This is the special system framebuffer represented by framebuffer id=0.

When creating a standalone context this property is not set since there are no default framebuffer.

Type: Framebuffer

Context.fbo: moderngl.Framebuffer#

The active framebuffer. Set every time Framebuffer.use() is called.

Type: Framebuffer

Context.front_face: str#

The front_face. Acceptable values are 'ccw' (default) or 'cw'.

Face culling must be enabled for this to have any effect: ctx.enable(moderngl.CULL_FACE).

Example:

# Triangles winded counter-clockwise considered front facing
ctx.front_face = 'ccw'
# Triangles winded clockwise considered front facing
ctx.front_face = 'cw'

Type: str

Context.cull_face: str#

The face side to cull. Acceptable values are 'back' (default) 'front' or 'front_and_back'.

This is similar to Context.front_face()

Face culling must be enabled for this to have any effect: ctx.enable(moderngl.CULL_FACE).

Example:

ctx.cull_face = 'front'
ctx.cull_face = 'back'
ctx.cull_face = 'front_and_back'

Type: str

Context.wireframe: bool#

Wireframe settings for debugging.

Type: bool

Context.max_samples: int#

The maximum supported number of samples for multisampling.

Type: int

Context.max_integer_samples: int#

The max integer samples.

Type: int

Context.max_texture_units: int#

The max texture units.

Type: int

Context.default_texture_unit: int#

The default texture unit.

Type: int

Context.max_anisotropy: float#

The maximum value supported for anisotropic filtering.

Type: float

Context.multisample: bool#

Enable/disable multisample mode (GL_MULTISAMPLE).

This property is write only.

Example:

# Enable
ctx.multisample = True
# Disable
ctx.multisample = False

Type: bool

Context.patch_vertices: int#

The number of vertices that will be used to make up a single patch primitive.

Type: int

Context.provoking_vertex: int#

Specifies the vertex to be used as the source of data for flat shaded varyings.

Flatshading a vertex shader varying output (ie. flat out vec3 pos) means to assign all vetices of the primitive the same value for that output. The vertex from which these values is derived is known as the provoking vertex.

It can be configured to be the first or the last vertex.

This property is write only.

Example:

# Use first vertex
ctx.provoking_vertex = moderngl.FIRST_VERTEX_CONVENTION

# Use last vertex
ctx.provoking_vertex = moderngl.LAST_VERTEX_CONVENTION

Type: int

Context.polygon_offset: Tuple[float, float]#

Get or set the current polygon offset.

The tuple values represents two float values: unit and a factor:

ctx.polygon_offset = unit, factor

When drawing polygons, lines or points directly on top of exiting geometry the result is often not visually pleasant. We can experience z-fighting or partially fading fragments due to different primitives not being rasterized in the exact same way or simply depth buffer precision issues.

For example when visualizing polygons drawing a wireframe version on top of the original mesh, these issues are immediately apparent. Applying decals to surfaces is another common example.

The official documentation states the following:

When enabled, the depth value of each fragment is added
to a calculated offset value. The offset is added before
the depth test is performed and before the depth value
is written into the depth buffer. The offset value o is calculated by:
o = m * factor + r * units
where m is the maximum depth slope of the polygon and r is the smallest
value guaranteed to produce a resolvable difference in window coordinate
depth values. The value r is an implementation-specific constant.

In simpler terms: We use polygon offset to either add a positive offset to the geometry (push it away from you) or a negative offset to geometry (pull it towards you).

units is a constant offset to depth and will do the job alone
if we are working with geometry parallel to the near/far plane.
The factor helps you handle sloped geometry (not parallel to near/far plane).

In most cases you can get away with [-1.0, 1.0] for both factor and units, but definitely play around with the values. When both values are set to 0 polygon offset is disabled internally.

To just get started with something you can try:

# Either push the geomtry away or pull it towards you
# with support for handling small to medium sloped geometry
ctx.polygon_offset = 1.0, 1.0
ctx.polygon_offset = -1.0, -1.0

# Disable polygon offset
ctx.polygon_offset = 0, 0

Type: tuple

Context.error: str#

The result of glGetError() but human readable.

This values is provided for debug purposes only and is likely to reduce performace when used in a draw loop.

Type: str

Context.extensions: Set[str]#

The extensions supported by the context.

All extensions names have a GL_ prefix, so if the spec refers to ARB_compute_shader we need to look for GL_ARB_compute_shader:

# If compute shaders are supported ...
>> 'GL_ARB_compute_shader' in ctx.extensions
True

Example data:

{
    'GL_ARB_multi_bind',
    'GL_ARB_shader_objects',
    'GL_ARB_half_float_vertex',
    'GL_ARB_map_buffer_alignment',
    'GL_ARB_arrays_of_arrays',
    'GL_ARB_pipeline_statistics_query',
    'GL_ARB_provoking_vertex',
    'GL_ARB_gpu_shader5',
    'GL_ARB_uniform_buffer_object',
    'GL_EXT_blend_equation_separate',
    'GL_ARB_tessellation_shader',
    'GL_ARB_multi_draw_indirect',
    'GL_ARB_multisample',
    .. etc ..
}

Type: Set[str]

Context.info: Dict[str, Any]#

OpenGL Limits and information about the context.

Example:

# The maximum width and height of a texture
>> ctx.info['GL_MAX_TEXTURE_SIZE']
16384

# Vendor and renderer
>> ctx.info['GL_VENDOR']
NVIDIA Corporation
>> ctx.info['GL_RENDERER']
NVIDIA GeForce GT 650M OpenGL Engine

Example data:

{
    'GL_VENDOR': 'NVIDIA Corporation',
    'GL_RENDERER': 'NVIDIA GeForce GT 650M OpenGL Engine',
    'GL_VERSION': '4.1 NVIDIA-10.32.0 355.11.10.10.40.102',
    'GL_POINT_SIZE_RANGE': (1.0, 2047.0),
    'GL_SMOOTH_LINE_WIDTH_RANGE': (0.5, 1.0),
    'GL_ALIASED_LINE_WIDTH_RANGE': (1.0, 1.0),
    'GL_POINT_FADE_THRESHOLD_SIZE': 1.0,
    'GL_POINT_SIZE_GRANULARITY': 0.125,
    'GL_SMOOTH_LINE_WIDTH_GRANULARITY': 0.125,
    'GL_MIN_PROGRAM_TEXEL_OFFSET': -8.0,
    'GL_MAX_PROGRAM_TEXEL_OFFSET': 7.0,
    'GL_MINOR_VERSION': 1,
    'GL_MAJOR_VERSION': 4,
    'GL_SAMPLE_BUFFERS': 0,
    'GL_SUBPIXEL_BITS': 8,
    'GL_CONTEXT_PROFILE_MASK': 1,
    'GL_UNIFORM_BUFFER_OFFSET_ALIGNMENT': 256,
    'GL_DOUBLEBUFFER': False,
    'GL_STEREO': False,
    'GL_MAX_VIEWPORT_DIMS': (16384, 16384),
    'GL_MAX_3D_TEXTURE_SIZE': 2048,
    'GL_MAX_ARRAY_TEXTURE_LAYERS': 2048,
    'GL_MAX_CLIP_DISTANCES': 8,
    'GL_MAX_COLOR_ATTACHMENTS': 8,
    'GL_MAX_COLOR_TEXTURE_SAMPLES': 8,
    'GL_MAX_COMBINED_FRAGMENT_UNIFORM_COMPONENTS': 233472,
    'GL_MAX_COMBINED_GEOMETRY_UNIFORM_COMPONENTS': 231424,
    'GL_MAX_COMBINED_TEXTURE_IMAGE_UNITS': 80,
    'GL_MAX_COMBINED_UNIFORM_BLOCKS': 70,
    'GL_MAX_COMBINED_VERTEX_UNIFORM_COMPONENTS': 233472,
    'GL_MAX_CUBE_MAP_TEXTURE_SIZE': 16384,
    'GL_MAX_DEPTH_TEXTURE_SAMPLES': 8,
    'GL_MAX_DRAW_BUFFERS': 8,
    'GL_MAX_DUAL_SOURCE_DRAW_BUFFERS': 1,
    'GL_MAX_ELEMENTS_INDICES': 150000,
    'GL_MAX_ELEMENTS_VERTICES': 1048575,
    'GL_MAX_FRAGMENT_INPUT_COMPONENTS': 128,
    'GL_MAX_FRAGMENT_UNIFORM_COMPONENTS': 4096,
    'GL_MAX_FRAGMENT_UNIFORM_VECTORS': 1024,
    'GL_MAX_FRAGMENT_UNIFORM_BLOCKS': 14,
    'GL_MAX_GEOMETRY_INPUT_COMPONENTS': 128,
    'GL_MAX_GEOMETRY_OUTPUT_COMPONENTS': 128,
    'GL_MAX_GEOMETRY_TEXTURE_IMAGE_UNITS': 16,
    'GL_MAX_GEOMETRY_UNIFORM_BLOCKS': 14,
    'GL_MAX_GEOMETRY_UNIFORM_COMPONENTS': 2048,
    'GL_MAX_INTEGER_SAMPLES': 1,
    'GL_MAX_SAMPLES': 8,
    'GL_MAX_RECTANGLE_TEXTURE_SIZE': 16384,
    'GL_MAX_RENDERBUFFER_SIZE': 16384,
    'GL_MAX_SAMPLE_MASK_WORDS': 1,
    'GL_MAX_SERVER_WAIT_TIMEOUT': -1,
    'GL_MAX_TEXTURE_BUFFER_SIZE': 134217728,
    'GL_MAX_TEXTURE_IMAGE_UNITS': 16,
    'GL_MAX_TEXTURE_LOD_BIAS': 15,
    'GL_MAX_TEXTURE_SIZE': 16384,
    'GL_MAX_UNIFORM_BUFFER_BINDINGS': 70,
    'GL_MAX_UNIFORM_BLOCK_SIZE': 65536,
    'GL_MAX_VARYING_COMPONENTS': 0,
    'GL_MAX_VARYING_VECTORS': 31,
    'GL_MAX_VARYING_FLOATS': 0,
    'GL_MAX_VERTEX_ATTRIBS': 16,
    'GL_MAX_VERTEX_TEXTURE_IMAGE_UNITS': 16,
    'GL_MAX_VERTEX_UNIFORM_COMPONENTS': 4096,
    'GL_MAX_VERTEX_UNIFORM_VECTORS': 1024,
    'GL_MAX_VERTEX_OUTPUT_COMPONENTS': 128,
    'GL_MAX_VERTEX_UNIFORM_BLOCKS': 14,
    'GL_MAX_VERTEX_ATTRIB_RELATIVE_OFFSET': 0,
    'GL_MAX_VERTEX_ATTRIB_BINDINGS': 0,
    'GL_VIEWPORT_BOUNDS_RANGE': (-32768, 32768),
    'GL_VIEWPORT_SUBPIXEL_BITS': 0,
    'GL_MAX_VIEWPORTS': 16
}

Type: dict

Context.mglo: Any#: Internal representation for debug purposes only.

Context.extra: Any#: Any - Attribute for storing user defined objects

Context Flags#

Context flags are used to enable or disable states in the context. These are not the same enum values as in opengl, but are rather bit flags so we can or them together setting multiple states in a simple way.

These values are available in the Context object and in the moderngl module when you don’t have access to the context.

import moderngl

# From moderngl
ctx.enable_only(moderngl.DEPTH_TEST | moderngl.CULL_FACE)

# From context
ctx.enable_only(ctx.DEPTH_TEST | ctx.CULL_FACE)

Context.NOTHING: moderngl.Constant#: Represents no states. Can be used with Context.enable_only() to disable all states.

Context.BLEND: moderngl.Constant#: Enable/disable blending

Context.DEPTH_TEST: moderngl.Constant#: Enable/disable depth testing

Context.CULL_FACE: moderngl.Constant#: Enable/disable face culling

Context.RASTERIZER_DISCARD: moderngl.Constant#

Enable/disable rasterization

Context flag: Enables gl_PointSize in vertex or geometry shaders.

When enabled we can write to gl_PointSize in the vertex shader to specify the point size for each individual point.

If this value is not set in the shader the behavior is undefined. This means the points may or may not appear depending if the drivers enforce some default value for gl_PointSize.

Context.PROGRAM_POINT_SIZE: moderngl.Constant#: When disabled Context.point_size is used.

Primitive Modes#

Context.POINTS: moderngl.Constant#: Each vertex represents a point

Context.LINES: moderngl.Constant#: Vertices 0 and 1 are considered a line. Vertices 2 and 3 are considered a line. And so on. If the user specifies a non-even number of vertices, then the extra vertex is ignored.

Context.LINE_LOOP: moderngl.Constant#: As line strips, except that the first and last vertices are also used as a line. Thus, you get n lines for n input vertices. If the user only specifies 1 vertex, the drawing command is ignored. The line between the first and last vertices happens after all of the previous lines in the sequence.

Context.LINE_STRIP: moderngl.Constant#: The adjacent vertices are considered lines. Thus, if you pass n vertices, you will get n-1 lines. If the user only specifies 1 vertex, the drawing command is ignored.

Context.TRIANGLES: moderngl.Constant#: Vertices 0, 1, and 2 form a triangle. Vertices 3, 4, and 5 form a triangle. And so on.

Context.TRIANGLE_STRIP: moderngl.Constant#: Every group of 3 adjacent vertices forms a triangle. The face direction of the strip is determined by the winding of the first triangle. Each successive triangle will have its effective face order reversed, so the system compensates for that by testing it in the opposite way. A vertex stream of n length will generate n-2 triangles.

Context.TRIANGLE_FAN: moderngl.Constant#: The first vertex is always held fixed. From there on, every group of 2 adjacent vertices form a triangle with the first. So with a vertex stream, you get a list of triangles like so: (0, 1, 2) (0, 2, 3), (0, 3, 4), etc. A vertex stream of n length will generate n-2 triangles.

Context.LINES_ADJACENCY: moderngl.Constant#: These are special primitives that are expected to be used specifically with geomtry shaders. These primitives give the geometry shader more vertices to work with for each input primitive. Data needs to be duplicated in buffers.

Context.LINE_STRIP_ADJACENCY: moderngl.Constant#: These are special primitives that are expected to be used specifically with geomtry shaders. These primitives give the geometry shader more vertices to work with for each input primitive. Data needs to be duplicated in buffers.

Context.TRIANGLES_ADJACENCY: moderngl.Constant#: These are special primitives that are expected to be used specifically with geomtry shaders. These primitives give the geometry shader more vertices to work with for each input primitive. Data needs to be duplicated in buffers.

Context.TRIANGLE_STRIP_ADJACENCY: moderngl.Constant#: These are special primitives that are expected to be used specifically with geomtry shaders. These primitives give the geometry shader more vertices to work with for each input primitive. Data needs to be duplicated in buffers.

Context.PATCHES: moderngl.Constant#: primitive type can only be used when Tessellation is active. It is a primitive with a user-defined number of vertices, which is then tessellated based on the control and evaluation shaders into regular points, lines, or triangles, depending on the TES’s settings.

Texture Filters#

Also available in the Context instance including mode details.

Context.NEAREST: moderngl.Constant#: Returns the value of the texture element that is nearest (in Manhattan distance) to the specified texture coordinates.

Context.LINEAR: moderngl.Constant#: Returns the weighted average of the four texture elements that are closest to the specified texture coordinates. These can include items wrapped or repeated from other parts of a texture, depending on the values of texture repeat mode, and on the exact mapping.

Context.NEAREST_MIPMAP_NEAREST: moderngl.Constant#: Chooses the mipmap that most closely matches the size of the pixel being textured and uses the NEAREST criterion (the texture element closest to the specified texture coordinates) to produce a texture value.

Context.LINEAR_MIPMAP_NEAREST: moderngl.Constant#: Chooses the mipmap that most closely matches the size of the pixel being textured and uses the LINEAR criterion (a weighted average of the four texture elements that are closest to the specified texture coordinates) to produce a texture value.

Context.NEAREST_MIPMAP_LINEAR: moderngl.Constant#: Chooses the two mipmaps that most closely match the size of the pixel being textured and uses the NEAREST criterion (the texture element closest to the specified texture coordinates ) to produce a texture value from each mipmap. The final texture value is a weighted average of those two values.

Context.LINEAR_MIPMAP_LINEAR: moderngl.Constant#: Chooses the two mipmaps that most closely match the size of the pixel being textured and uses the LINEAR criterion (a weighted average of the texture elements that are closest to the specified texture coordinates) to produce a texture value from each mipmap. The final texture value is a weighted average of those two values.

Blend Functions#

Blend functions are used with Context.blend_func to control blending operations.

# Default value
ctx.blend_func = ctx.SRC_ALPHA, ctx.ONE_MINUS_SRC_ALPHA

Context.ZERO: moderngl.Constant#: (0,0,0,0)

Context.ONE: moderngl.Constant#: (1,1,1,1)

Context.SRC_COLOR: moderngl.Constant#: (Rs0/kR,Gs0/kG,Bs0/kB,As0/kA)

Context.ONE_MINUS_SRC_COLOR: moderngl.Constant#: (1,1,1,1) - (Rs0/kR,Gs0/kG,Bs0/kB,As0/kA)

Context.SRC_ALPHA: moderngl.Constant#: (As0/kA,As0/kA,As0/kA,As0/kA)

Context.ONE_MINUS_SRC_ALPHA: moderngl.Constant#: (1,1,1,1) - (As0/kA,As0/kA,As0/kA,As0/kA)

Context.DST_ALPHA: moderngl.Constant#: (Ad/kA,Ad/kA,Ad/kA,Ad/kA)

Context.ONE_MINUS_DST_ALPHA: moderngl.Constant#: (1,1,1,1) - (Ad/kA,Ad/kA,Ad/kA,Ad/kA)

Context.DST_COLOR: moderngl.Constant#: (Rd/kR,Gd/kG,Bd/kB,Ad/kA)

Context.ONE_MINUS_DST_COLOR: moderngl.Constant#: (1,1,1,1) - (Rd/kR,Gd/kG,Bd/kB,Ad/kA)

Blend Function Shortcuts#

Context.DEFAULT_BLENDING: moderngl.Constant#: Shotcut for the default blending SRC_ALPHA, ONE_MINUS_SRC_ALPHA

Context.ADDITIVE_BLENDING: moderngl.Constant#: Shotcut for additive blending ONE, ONE

Context.PREMULTIPLIED_ALPHA: moderngl.Constant#: Shotcut for blend mode when using premultiplied alpha SRC_ALPHA, ONE

Blend Equations#

Used with Context.blend_equation.

Context.FUNC_ADD: moderngl.Constant#: source + destination

Context.FUNC_SUBTRACT: moderngl.Constant#: source - destination

Context.FUNC_REVERSE_SUBTRACT: moderngl.Constant#: destination - source

Context.MIN: moderngl.Constant#: Minimum of source and destination

Context.MAX: moderngl.Constant#: Maximum of source and destination

Other Enums#

Context.FIRST_VERTEX_CONVENTION: moderngl.Constant#: Specifies the first vertex should be used as the source of data for flat shaded varyings. Used with Context.provoking_vertex.

Context.LAST_VERTEX_CONVENTION: moderngl.Constant#: Specifies the last vertex should be used as the source of data for flat shaded varyings. Used with Context.provoking_vertex.

Examples#

ModernGL Context#

import moderngl
# create a window
ctx = moderngl.create_context()
print(ctx.version_code)

Standalone ModernGL Context#

import moderngl
ctx = moderngl.create_standalone_context()
print(ctx.version_code)

ContextManager#

context_manager.py

import moderngl


class ContextManager:
    ctx = None

    @staticmethod
    def get_default_context(allow_fallback_standalone_context=True) -> moderngl.Context:
        '''
            Default context
        '''

        if ContextManager.ctx is None:
            try:
                ContextManager.ctx = moderngl.create_context()
            except:
                if allow_fallback_standalone_context:
                    ContextManager.ctx = moderngl.create_standalone_context()
                else:
                    raise

        return ContextManager.ctx

example.py

from context_manager import ContextManager

ctx = ContextManager.get_default_context()
print(ctx.version_code)

Buffer#

class moderngl.Buffer#

Buffer objects are OpenGL objects that store an array of unformatted memory allocated by the OpenGL context, (data allocated on the GPU).

These can be used to store vertex data, pixel data retrieved from images or the framebuffer, and a variety of other things.

A Buffer object cannot be instantiated directly, it requires a context. Use Context.buffer() to create one.

Copy buffer content using Context.copy_buffer().

Create#

Context.buffer(data: Optional[Any] = None, *, reserve: int = 0, dynamic: bool = False) → moderngl.Buffer

Create a Buffer object.

Parameters

data (bytes) – Content of the new buffer.

Keyword Arguments

reserve (int) – The number of bytes to reserve.
dynamic (bool) – Treat buffer as dynamic.

Returns

Buffer object

Methods#

Buffer.assign(index: int) → Tuple[moderngl.Buffer, int]#

Helper method for assigning a buffer.

Returns: (self, index) tuple

Buffer.bind(*attribs, layout=None)#

Helper method for binding a buffer.

Returns: (self, layout, attribs) tuple

Buffer.write(data: Any, *, offset: int = 0) → None#

Write the content.

Parameters: data (bytes) – The data.
Keyword Arguments: offset (int) – The offset in bytes.

Buffer.write_chunks(data: Any, start: int, step: int, count: int) → None#

Split data to count equal parts.

Write the chunks using offsets calculated from start, step and stop.

Parameters

data (bytes) – The data.
start (int) – First offset in bytes.
step (int) – Offset increment in bytes.
count (int) – The number of offsets.

Buffer.read(size: int = - 1, *, offset: int = 0) → bytes#

Read the content.

Parameters: size (int) – The size in bytes. Value -1 means all.
Keyword Arguments: offset (int) – The offset in bytes.
Returns: bytes

Buffer.read_into(buffer: Any, size: int = - 1, *, offset: int = 0, write_offset: int = 0) → None#

Read the content into a buffer.

Parameters

buffer (bytearray) – The buffer that will receive the content.
size (int) – The size in bytes. Value -1 means all.

Keyword Arguments

offset (int) – The read offset in bytes.
write_offset (int) – The write offset in bytes.

Buffer.read_chunks(chunk_size: int, start: int, step: int, count: int) → bytes#

Read the content.

Read and concatenate the chunks of size chunk_size using offsets calculated from start, step and stop.

Parameters

chunk_size (int) – The chunk size in bytes.
start (int) – First offset in bytes.
step (int) – Offset increment in bytes.
count (int) – The number of offsets.

Returns

bytes

Buffer.read_chunks_into(buffer: Any, chunk_size: int, start: int, step: int, count: int, *, write_offset: int = 0) → None#

Read the content.

Read and concatenate the chunks of size chunk_size using offsets calculated from start, step and stop.

Parameters

buffer (bytearray) – The buffer that will receive the content.
chunk_size (int) – The chunk size.
start (int) – First offset.
step (int) – Offset increment.
count (int) – The number of offsets.

Keyword Arguments

write_offset (int) – The write offset.

Buffer.clear(size: int = - 1, *, offset: int = 0, chunk: Optional[Any] = None) → None#

Clear the content.

Parameters

size (int) – The size. Value -1 means all.

Keyword Arguments

offset (int) – The offset.
chunk (bytes) – The chunk to use repeatedly.

Buffer.bind_to_uniform_block(binding: int = 0, *, offset: int = 0, size: int = - 1) → None#

Bind the buffer to a uniform block.

Parameters

binding (int) – The uniform block binding.

Keyword Arguments

offset (int) – The offset.
size (int) – The size. Value -1 means all.

Buffer.bind_to_storage_buffer(binding: int = 0, *, offset: int = 0, size: int = - 1) → None#

Bind the buffer to a shader storage buffer.

Parameters

binding (int) – The shader storage binding.

Keyword Arguments

offset (int) – The offset.
size (int) – The size. Value -1 means all.

Buffer.orphan(size: int = - 1) → None#

Orphan the buffer with the option to specify a new size.

It is also called buffer re-specification.

Reallocate the buffer object before you start modifying it.

Since allocating storage is likely faster than the implicit synchronization, you gain significant performance advantages over synchronization.

The old storage will still be used by the OpenGL commands that have been sent previously. It is likely that the GL driver will not be doing any allocation at all, but will just be pulling an old free block off the unused buffer queue and use it, so it is likely to be very efficient.

Keyword Arguments: size (int) – The new byte size if the buffer. If not supplied the buffer size will be unchanged.

Example

# For simplicity the VertexArray creation is omitted

>>> vbo = ctx.buffer(reserve=1024)

# Fill the buffer

>>> vbo.write(some_temporary_data)

# Issue a render call that uses the vbo

>>> vao.render(...)

# Orphan the buffer

>>> vbo.orphan()

# Issue another render call without waiting for the previous one

>>> vbo.write(some_temporary_data)
>>> vao.render(...)

# We can also resize the buffer. In this case we double the size

>> vbo.orphan(vbo.size * 2)

Buffer.release() → None#: Release the ModernGL object.

Attributes#

Buffer.size: int#

The size of the buffer in bytes.

Type: int

Buffer.dynamic: bool#

Is the buffer created with the dynamic flag?.

Type: bool

Buffer.glo: int#

The internal OpenGL object.

This values is provided for debug purposes only.

Type: int

Buffer.mglo: Any#: Internal representation for debug purposes only.

Buffer.extra: Any#: Any - Attribute for storing user defined objects

Buffer.ctx: moderngl.Context#: The context this object belongs to

VertexArray#

class moderngl.VertexArray#

A VertexArray object is an OpenGL object that stores all of the state needed to supply vertex data.

It stores the format of the vertex data as well as the Buffer objects providing the vertex data arrays.

In ModernGL, the VertexArray object also stores a reference for a Program object, and some Subroutine information.

A VertexArray object cannot be instantiated directly, it requires a context. Use Context.vertex_array() or Context.simple_vertex_array() to create one.

Note

Compared to OpenGL, VertexArray objects have some additional responsibilities:

Binding a Program when VertexArray.render() or VertexArray.transform() is called.
Subroutines can be assigned. Please see the example below.

Create#

Create a VertexArray object.

Warning

This method is deprecated and may be removed in the future. Use Context.vertex_array() instead. It also supports the argument format this method describes.

Parameters

program (Program) – The program used when rendering.
buffer (Buffer) – The buffer.
attributes (list) – A list of attribute names.

Keyword Arguments

index_element_size (int) – byte size of each index element, 1, 2 or 4.
index_buffer (Buffer) – An index buffer.
mode (int) – The default draw mode (for example: TRIANGLES)

Returns

VertexArray object

Context.vertex_array(*args, **kwargs) → moderngl.VertexArray

Create a VertexArray object.

Examples:

# Empty vertext array (no attribute input)
vao = ctx.vertex_array(program)

# Simple version with a single buffer
vao = ctx.vertex_array(program, buffer, 'in_position', 'in_normal')
vao = ctx.vertex_array(program, buffer, 'in_position', 'in_normal', index_buffer=ibo)

# Multiple buffers
vao = ctx.vertex_array(program, [
    (buffer1, '3f', 'in_position'),
    (buffer2, '3f', 'in_normal'),
])
vao = ctx.vertex_array(program, [
        (buffer1, '3f', 'in_position'),
        (buffer2, '3f', 'in_normal'),
    ],
    index_buffer=ibo,
    index_element_size=2,  # 16 bit / 'u2' index buffer
)

This method also supports arguments for Context.simple_vertex_array().

Parameters

program (Program) – The program used when rendering
content (list) – A list of (buffer, format, attributes). See Buffer Format.

Keyword Arguments

index_buffer (Buffer) – An index buffer (optional)
index_element_size (int) – byte size of each index element, 1, 2 or 4.
skip_errors (bool) – Ignore errors during creation
mode (int) – The default draw mode (for example: TRIANGLES)

Returns

VertexArray object

Methods#

VertexArray.render(mode: Optional[int] = None, vertices: int = - 1, *, first: int = 0, instances: int = - 1) → None#

The render primitive (mode) must be the same as the input primitive of the GeometryShader.

Parameters

mode (int) – By default TRIANGLES will be used.
vertices (int) – The number of vertices to transform.

Keyword Arguments

first (int) – The index of the first vertex to start with.
instances (int) – The number of instances.

VertexArray.render_indirect(buffer: moderngl.Buffer, mode: Optional[int] = None, count: int = - 1, *, first: int = 0) → None#

The render primitive (mode) must be the same as the input primitive of the GeometryShader.

The draw commands are 5 integers: (count, instanceCount, firstIndex, baseVertex, baseInstance).

Parameters

buffer (Buffer) – Indirect drawing commands.
mode (int) – By default TRIANGLES will be used.
count (int) – The number of draws.

Keyword Arguments

first (int) – The index of the first indirect draw command.

VertexArray.transform(buffer: Union[moderngl.Buffer, List[moderngl.Buffer]], mode: Optional[int] = None, vertices: int = - 1, *, first: int = 0, instances: int = - 1, buffer_offset: int = 0) → None#

Transform vertices.

Stores the output in a single buffer. The transform primitive (mode) must be the same as the input primitive of the GeometryShader.

Parameters

buffer (Buffer) – The buffer to store the output.
mode (int) – By default POINTS will be used.
vertices (int) – The number of vertices to transform.

Keyword Arguments

first (int) – The index of the first vertex to start with.
instances (int) – The number of instances.
buffer_offset (int) – Byte offset for the output buffer

VertexArray.bind(attribute: int, cls: str, buffer: moderngl.Buffer, fmt: str, *, offset: int = 0, stride: int = 0, divisor: int = 0, normalize: bool = False) → None#

Bind individual attributes to buffers.

Parameters

location (int) – The attribute location.
cls (str) – The attribute class. Valid values are f, i or d.
buffer (Buffer) – The buffer.
format (str) – The buffer format.

Keyword Arguments

offset (int) – The offset.
stride (int) – The stride.
divisor (int) – The divisor.
normalize (bool) – The normalize parameter, if applicable.

VertexArray.release() → None#: Release the ModernGL object.

Attributes#

VertexArray.mode: int#

Get or set the default rendering mode.

This value is used when mode is not passed in rendering calls.

Examples:

vao.mode = moderngl.TRIANGLE_STRIPS

Type: int

VertexArray.program: moderngl.Program#

The program assigned to the VertexArray.

The program used when rendering or transforming primitives.

Type: Program

VertexArray.index_buffer: moderngl.Buffer#

The index buffer if the index_buffer is set, otherwise None.

Type: Buffer

VertexArray.index_element_size: int#

The byte size of each element in the index buffer.

Type: int

VertexArray.scope: Optional[moderngl.Scope]#: The scope to use while rendering.

VertexArray.vertices: int#

The number of vertices detected.

This is the minimum of the number of vertices possible per Buffer. The size of the index_buffer determines the number of vertices. Per instance vertex attributes does not affect this number.

Type: int

VertexArray.instances: int#

Get or set the number of instances to render.

Type: int

VertexArray.subroutines: Tuple[int, ...]#

The subroutines assigned to the VertexArray.

The subroutines used when rendering or transforming primitives.

Type: tuple

VertexArray.glo: int#

The internal OpenGL object.

This values is provided for debug purposes only.

Type: int

VertexArray.mglo: Any#: Internal representation for debug purposes only.

VertexArray.extra: Any#: Any - Attribute for storing user defined objects

VertexArray.ctx: moderngl.Context#: The context this object belongs to

Program#

class moderngl.Program#

A Program object represents fully processed executable code in the OpenGL Shading Language, for one or more Shader stages.

In ModernGL, a Program object can be assigned to VertexArray objects. The VertexArray object is capable of binding the Program object once the VertexArray.render() or VertexArray.transform() is called.

Program objects has no method called use(), VertexArrays encapsulate this mechanism.

A Program object cannot be instantiated directly, it requires a context. Use Context.program() to create one.

Uniform buffers can be bound using Buffer.bind_to_uniform_block() or can be set individually. For more complex binding yielding higher performance consider using moderngl.Scope.

Create#

Create a Program object.

The varyings are only used when a transform program is created to specify the names of the output varyings to capture in the output buffer.

fragment_outputs can be used to programmatically map named fragment shader outputs to a framebuffer attachment numbers. This can also be done by using layout(location=N) in the fragment shader.

Parameters

vertex_shader (str) – The vertex shader source.
fragment_shader (str) – The fragment shader source.
geometry_shader (str) – The geometry shader source.
tess_control_shader (str) – The tessellation control shader source.
tess_evaluation_shader (str) – The tessellation evaluation shader source.
varyings (list) – A list of varyings.
fragment_outputs (dict) – A dictionary of fragment outputs.

Returns

Program object

Methods#

Program.get(key: str, default: Any) → Union[moderngl.Uniform, moderngl.UniformBlock, moderngl.Subroutine, moderngl.Attribute, moderngl.Varying]#

Returns a Uniform, UniformBlock, Subroutine, Attribute or Varying.

Parameters: default – This is the value to be returned in case key does not exist.
Returns: Uniform, UniformBlock, Subroutine, Attribute or Varying

Program.__getitem__(key: str) → Union[moderngl.Uniform, moderngl.UniformBlock, moderngl.Subroutine, moderngl.Attribute, moderngl.Varying]#

Get a member such as uniforms, uniform blocks, subroutines, attributes and varyings by name.

# Get a uniform
uniform = program['color']

# Uniform values can be set on the returned object
# or the `__setitem__` shortcut can be used.
program['color'].value = 1.0, 1.0, 1.0, 1.0

# Still when writing byte data we need to use the `write()` method
program['color'].write(buffer)

Program.__setitem__(key: str, value: Any) → None#

Set a value of uniform or uniform block.

# Set a vec4 uniform
uniform['color'] = 1.0, 1.0, 1.0, 1.0

# Optionally we can store references to a member and set the value directly
uniform = program['color']
uniform.value = 1.0, 0.0, 0.0, 0.0

uniform = program['cameraMatrix']
uniform.write(camera_matrix)

Program.__iter__() → Generator[str, None, None]#

Yields the internal members names as strings.

This includes all members such as uniforms, attributes etc.

Example:

# Print member information
for name in program:
    member = program[name]
    print(name, type(member), member)

Output:

vert <class 'moderngl.program_members.attribute.Attribute'> <Attribute: 0>
vert_color <class 'moderngl.program_members.attribute.Attribute'> <Attribute: 1>
gl_InstanceID <class 'moderngl.program_members.attribute.Attribute'> <Attribute: -1>
rotation <class 'moderngl.program_members.uniform.Uniform'> <Uniform: 0>
scale <class 'moderngl.program_members.uniform.Uniform'> <Uniform: 1>

We can filter on member type if needed:

for name in prog:
    member = prog[name]
    if isinstance(member, moderngl.Uniform):
        print('Uniform', name, member)

or a less verbose version using dict comprehensions:

uniforms = {name: self.prog[name] for name in self.prog
            if isinstance(self.prog[name], moderngl.Uniform)}
print(uniforms)

Output:

{'rotation': <Uniform: 0>, 'scale': <Uniform: 1>}

Program.__eq__(value, /)#: Return self==value.

Program.release() → None#: Release the ModernGL object.

Attributes#

Program.geometry_input: int#

The geometry input primitive.

The GeometryShader’s input primitive if the GeometryShader exists. The geometry input primitive will be used for validation. (from layout(input_primitive) in;)

This can only be POINTS, LINES, LINES_ADJACENCY, TRIANGLES, TRIANGLE_ADJACENCY.

Type: int

Program.geometry_output: int#

The geometry output primitive.

The GeometryShader’s output primitive if the GeometryShader exists. This can only be POINTS, LINE_STRIP and TRIANGLE_STRIP (from layout(output_primitive, max_vertices = vert_count) out;)

Type: int

Program.geometry_vertices: int#

The maximum number of vertices that.

the geometry shader will output. (from layout(output_primitive, max_vertices = vert_count) out;)

Type: int

Program.subroutines: Tuple[str, ...]#

The subroutine uniforms.

Type: tuple

Program.glo: int#

The internal OpenGL object.

This values is provided for debug purposes only.

Type: int

Program.mglo: Any#: Internal representation for debug purposes only.

Program.extra: Any#: Any - Attribute for storing user defined objects

Program.is_transform: bool#

If this is a tranform program (no fragment shader).

Type: bool

Program.ctx: moderngl.Context#: The context this object belongs to

Examples#

A simple program designed for rendering

my_render_program = ctx.program(
    vertex_shader='''
        #version 330

        in vec2 vert;

        void main() {
            gl_Position = vec4(vert, 0.0, 1.0);
        }
    ''',
    fragment_shader='''
        #version 330

        out vec4 color;

        void main() {
            color = vec4(0.3, 0.5, 1.0, 1.0);
        }
    ''',
)

A simple program designed for transforming

my_transform_program = ctx.program(
    vertex_shader='''
        #version 330

        in vec4 vert;
        out float vert_length;

        void main() {
            vert_length = length(vert);
        }
    ''',
    varyings=['vert_length']
)

Program Members#

Uniform#

class moderngl.Uniform#

A uniform is a global GLSL variable declared with the ‘uniform’ storage qualifier.

These act as parameters that the user of a shader program can pass to that program.

In ModernGL, Uniforms can be accessed using Program.__getitem__() or Program.__iter__()

Methods#

Uniform.read() → bytes#: Read the value of the uniform.

Uniform.write(data: Any) → None#: Write the value of the uniform.

Attributes#

Uniform.location: int#

The location of the uniform.

The location holds the value returned by the glGetUniformLocation. To set the value of the uniform use the value instead.

Type: int

Uniform.dimension: int#

The dimension of the uniform.

GLSL type	dimension
sampler2D	1
sampler2DCube	1
sampler2DShadow	1
bool	1
bvec2	2
bvec3	3
bvec4	4
int	1
ivec2	2
ivec3	3
ivec4	4
uint	1
uvec2	2
uvec3	3
uvec4	4
float	1
vec2	2
vec3	3
vec4	4
double	1
dvec2	2
dvec3	3
dvec4	4
mat2	4
mat2x3	6
mat2x4	8
mat3x2	6
mat3	9
mat3x4	12
mat4x2	8
mat4x3	12
mat4	16
dmat2	4
dmat2x3	6
dmat2x4	8
dmat3x2	6
dmat3	9
dmat3x4	12
dmat4x2	8
dmat4x3	12
dmat4	16

Type: int

Uniform.array_length: int#

The length of the array of the uniform. The array_length is 1 for non array uniforms.

Type: int

Uniform.name: str#

The name of the uniform.

The name does not contain leading [0]. The name may contain [ ] when the uniform is part of a struct.

Type: str

Uniform.value: Any#

The value of the uniform.

Reading the value of the uniform may force the GPU to sync.

The value must be a tuple for non array uniforms. The value must be a list of tuples for array uniforms.

Uniform.extra: Any#: Attribute for storing user defined objects

Uniform.mglo: Any#: Internal moderngl core object

UniformBlock#

class moderngl.UniformBlock#: Uniform Block metadata

UniformBlock.binding: int#

The binding of the uniform block.

Type: int

UniformBlock.value: int#

The value of the uniform block.

Type: int

UniformBlock.name: str#

The name of the uniform block.

Type: str

UniformBlock.index: int#

The index of the uniform block.

Type: int

UniformBlock.size: int#

The size of the uniform block.

Type: int

UniformBlock.extra: Any#: Attribute for storing user defined objects

UniformBlock.mglo: Any#: Internal moderngl core object

Subroutine#

class moderngl.Subroutine#: This class represents a program subroutine.

Subroutine.index: int#

The index of the subroutine.

Type: int

Subroutine.name: str#

The name of the subroutine.

Type: str

Subroutine.extra: Any#: Attribute for storing user defined objects

Attribute#

class moderngl.Attribute#: This class represents a program attribute.

Attribute.location: int#

The location of the attribute.

The result of the glGetAttribLocation.

Type: int

Attribute.array_length: int#

If the attribute is an array the array_length.

is the length of the array otherwise 1.

Type: int

Attribute.dimension: int#

The attribute dimension.

GLSL type	dimension
int	1
ivec2	2
ivec3	3
ivec4	4
uint	1
uvec2	2
uvec3	3
uvec4	4
float	1
vec2	2
vec3	3
vec4	4
double	1
dvec2	2
dvec3	3
dvec4	4
mat2	4
mat2x3	6
mat2x4	8
mat3x2	6
mat3	9
mat3x4	12
mat4x2	8
mat4x3	12
mat4	16
dmat2	4
dmat2x3	6
dmat2x4	8
dmat3x2	6
dmat3	9
dmat3x4	12
dmat4x2	8
dmat4x3	12
dmat4	16

Type: int

Attribute.shape: int#

The shape is a single character, representing the scalar type of the attribute.

shape	GLSL types
`'i'`	int
`'i'`	ivec2 ivec3 ivec4
`'I'`	uint
`'I'`	uvec2 uvec3 uvec4
`'f'`	float
	vec2 vec3 vec4
	mat2 mat3 mat4
	mat2x3 mat2x4 mat3x4 mat4x2 mat4x2 mat4x3
`'d'`	double
	dvec2 dvec3 dvec4
	dmat2 dmat3 dmat4
	dmat2x3 dmat2x4 dmat3x4 dmat4x2 dmat4x2 dmat4x3

Type: str

Attribute.name: str#

The attribute name.

The name will be filtered to have no array syntax on it’s end. Attribute name without '[0]' ending if any.

Type: str

Attribute.extra: Any#: Attribute for storing user defined objects

Varying#

class moderngl.Varying#: This class represents a program varying.

Varying.name: str#

The name of the varying.

Type: str

Varying.number: int#

The number of the varying.

Type: int

Varying.extra: Any#: Attribute for storing user defined objects

Sampler#

class moderngl.Sampler#

A Sampler Object is an OpenGL Object that stores the sampling parameters for a Texture access inside of a shader.

When a sampler object is bound to a texture image unit, the internal sampling parameters for a texture bound to the same image unit are all ignored. Instead, the sampling parameters are taken from this sampler object.

Unlike textures, a samplers state can also be changed freely be at any time without the sampler object being bound/in use.

Samplers are bound to a texture unit and not a texture itself. Be careful with leaving samplers bound to texture units as it can cause texture incompleteness issues (the texture bind is ignored).

Sampler bindings do clear automatically between every frame so a texture unit need at least one bind/use per frame.

Create#

Create a Sampler object.

Keyword Arguments

repeat_x (bool) – Repeat texture on x
repeat_y (bool) – Repeat texture on y
repeat_z (bool) – Repeat texture on z
filter (tuple) – The min and max filter
anisotropy (float) – Number of samples for anisotropic filtering. Any value greater than 1.0 counts as a use of anisotropic filtering
compare_func – Compare function for depth textures
border_color (tuple) – The (r, g, b, a) color for the texture border. When this value is set the repeat_ values are overridden setting the texture wrap to return the border color when outside [0, 1] range.
min_lod (float) – Minimum level-of-detail parameter (Default -1000.0). This floating-point value limits the selection of highest resolution mipmap (lowest mipmap level)
max_lod (float) – Minimum level-of-detail parameter (Default 1000.0). This floating-point value limits the selection of the lowest resolution mipmap (highest mipmap level)
texture (Texture) – The texture for this sampler

Methods#

Sampler.use(location: int = 0) → None#

Bind the sampler to a texture unit.

Parameters: location (int) – The texture unit

Sampler.clear(location: int = 0) → None#

Clear the sampler binding on a texture unit.

Parameters: location (int) – The texture unit

Sampler.assign(index: int) → Tuple[moderngl.Sampler, int]#

Helper method for assigning samplers to scopes.

Example:

s1 = ctx.sampler(...)
s2 = ctx.sampler(...)
ctx.scope(samplers=(s1.assign(0), s1.assign(1)), ...)

Returns: (self, index) tuple

Sampler.release() → None#: Release/destroy the ModernGL object.

Attributes#

Sampler.texture: Any#: texture

Sampler.repeat_x: bool#

The x repeat flag for the sampler (Default True).

Example:

# Enable texture repeat (GL_REPEAT)
sampler.repeat_x = True

# Disable texture repeat (GL_CLAMP_TO_EDGE)
sampler.repeat_x = False

Type: bool

Sampler.repeat_y: bool#

The y repeat flag for the sampler (Default True).

Example:

# Enable texture repeat (GL_REPEAT)
sampler.repeat_y = True

# Disable texture repeat (GL_CLAMP_TO_EDGE)
sampler.repeat_y = False

Type: bool

Sampler.repeat_z: bool#

The z repeat flag for the sampler (Default True).

Example:

# Enable texture repeat (GL_REPEAT)
sampler.repeat_z = True

# Disable texture repeat (GL_CLAMP_TO_EDGE)
sampler.repeat_z = False

Type: bool

Sampler.filter: Tuple[int, int]#

The minification and magnification filter for the sampler.

(Default (moderngl.LINEAR. moderngl.LINEAR))

Example:

sampler.filter == (moderngl.NEAREST, moderngl.NEAREST)
sampler.filter == (moderngl.LINEAR_MIPMAP_LINEAR, moderngl.LINEAR)
sampler.filter == (moderngl.NEAREST_MIPMAP_LINEAR, moderngl.NEAREST)
sampler.filter == (moderngl.LINEAR_MIPMAP_NEAREST, moderngl.NEAREST)

Type: tuple

Sampler.compare_func: str#

The compare function for a depth textures (Default '?').

By default samplers don’t have depth comparison mode enabled. This means that depth texture values can be read as a sampler2D using texture() in a GLSL shader by default.

When setting this property to a valid compare mode, GL_TEXTURE_COMPARE_MODE is set to GL_COMPARE_REF_TO_TEXTURE so that texture lookup functions in GLSL will return a depth comparison result instead of the actual depth value.

Accepted compare functions:

.compare_func = ''    # Disale depth comparison completely
sampler.compare_func = '<='  # GL_LEQUAL
sampler.compare_func = '<'   # GL_LESS
sampler.compare_func = '>='  # GL_GEQUAL
sampler.compare_func = '>'   # GL_GREATER
sampler.compare_func = '=='  # GL_EQUAL
sampler.compare_func = '!='  # GL_NOTEQUAL
sampler.compare_func = '0'   # GL_NEVER
sampler.compare_func = '1'   # GL_ALWAYS

Type: tuple

Sampler.anisotropy: float#

Number of samples for anisotropic filtering (Default 1.0).

The value will be clamped in range 1.0 and ctx.max_anisotropy.

Any value greater than 1.0 counts as a use of anisotropic filtering:

# Disable anisotropic filtering
sampler.anisotropy = 1.0

# Enable anisotropic filtering suggesting 16 samples as a maximum
sampler.anisotropy = 16.0

Type: float

Sampler.border_color: Tuple[float, float, float, float]#

The (r, g, b, a) color for the texture border (Default (0.0, 0.0, 0.0, 0.0)).

When setting this value the repeat_ values are overridden setting the texture wrap to return the border color when outside [0, 1] range.

Example:

# Red border color
sampler.border_color = (1.0, 0.0, 0.0, 0.0)

Type: tuple

Sampler.min_lod: float#

Minimum level-of-detail parameter (Default -1000.0).

This floating-point value limits the selection of highest resolution mipmap (lowest mipmap level)

Type: float

Sampler.max_lod: float#

Minimum level-of-detail parameter (Default 1000.0).

This floating-point value limits the selection of the lowest resolution mipmap (highest mipmap level)

Type: float

Sampler.extra: Any#: Any - Attribute for storing user defined objects

Sampler.mglo: Any#: Internal representation for debug purposes only.

Sampler.ctx: moderngl.Context#: The context this object belongs to

Texture#

class moderngl.Texture#

A Texture is an OpenGL object that contains one or more images that all have the same image format.

A texture can be used in two ways. It can be the source of a texture access from a Shader, or it can be used as a render target.

A Texture object cannot be instantiated directly, it requires a context. Use Context.texture() or Context.depth_texture() to create one.

Create#

Create a Texture object.

Warning

Do not play with internal_format unless you know exactly you are doing. This is an override to support sRGB and compressed textures if needed.

Parameters

size (tuple) – The width and height of the texture.
components (int) – The number of components 1, 2, 3 or 4.
data (bytes) – Content of the texture.

Keyword Arguments

samples (int) – The number of samples. Value 0 means no multisample format.
alignment (int) – The byte alignment 1, 2, 4 or 8.
dtype (str) – Data type.
internal_format (int) – Override the internalformat of the texture (IF needed)

Returns

Texture object

Context.depth_texture(size: Tuple[int, int], data: Optional[Any] = None, *, samples: int = 0, alignment: int = 4) → moderngl.Texture

Create a Texture object.

Parameters

size (tuple) – The width and height of the texture.
data (bytes) – Content of the texture.

Keyword Arguments

samples (int) – The number of samples. Value 0 means no multisample format.
alignment (int) – The byte alignment 1, 2, 4 or 8.

Returns

Texture object

Methods#

Texture.read(*, level: int = 0, alignment: int = 1) → bytes#

Read the pixel data as bytes into system memory.

The texture can also be attached to a Framebuffer to gain access to Framebuffer.read() for additional features such ad reading a subsection or converting to another dtype.

Keyword Arguments

level (int) – The mipmap level.
alignment (int) – The byte alignment of the pixels.

Returns

bytes

Texture.read_into(buffer: Any, *, level: int = 0, alignment: int = 1, write_offset: int = 0) → None#

Read the content of the texture into a bytearray or Buffer.

The advantage of reading into a Buffer is that pixel data does not need to travel all the way to system memory:

# Reading pixel data into a bytearray
data = bytearray(4)
texture = ctx.texture((2, 2), 1)
texture.read_into(data)

# Reading pixel data into a buffer
data = ctx.buffer(reserve=4)
texture = ctx.texture((2, 2), 1)
texture.read_into(data)

Parameters

buffer (Union[bytearray, Buffer]) – The buffer that will receive the pixels.

Keyword Arguments

level (int) – The mipmap level.
alignment (int) – The byte alignment of the pixels.
write_offset (int) – The write offset.

Texture.write(data: Any, viewport: Optional[Union[Tuple[int, int], Tuple[int, int, int, int]]] = None, *, level: int = 0, alignment: int = 1) → None#

Update the content of the texture from byte data or a moderngl Buffer.

Examples:

# Write data from a moderngl Buffer
data = ctx.buffer(reserve=4)
texture = ctx.texture((2, 2), 1)
texture.write(data)

# Write data from bytes
data = b'\xff\xff\xff\xff'
texture = ctx.texture((2, 2), 1)
texture.write(data)

# Write to a sub-section of the texture using viewport
texture = ctx.texture((100, 100), 4)
# Fill the lower left 50x50 pixels with new data
texture.write(data, viewport=(0, 0, 50, 50))

Parameters

data (Union[bytes, Buffer]) – The pixel data.
viewport (tuple) – The sub-section of the texture to update in viewport coordinates. The data size must match the size of the area.

Keyword Arguments

level (int) – The mipmap level.
alignment (int) – The byte alignment of the pixels.

Texture.build_mipmaps(base: int = 0, max_level: int = 1000) → None#

Generate mipmaps.

This also changes the texture filter to LINEAR_MIPMAP_LINEAR, LINEAR

Keyword Arguments

base (int) – The base level
max_level (int) – The maximum levels to generate

Texture.bind_to_image(unit: int, read: bool = True, write: bool = True, level: int = 0, format: int = 0) → None#

Bind a texture to an image unit (OpenGL 4.2 required).

This is used to bind textures to image units for shaders. The idea with image load/store is that the user can bind one of the images in a Texture to a number of image binding points (which are separate from texture image units). Shaders can read information from these images and write information to them, in ways that they cannot with textures.

It’s important to specify the right access type for the image. This can be set with the read and write arguments. Allowed combinations are:

Read-only: read=True and write=False
Write-only: read=False and write=True
Read-write: read=True and write=True

format specifies the format that is to be used when performing formatted stores into the image from shaders. format must be compatible with the texture’s internal format. By default the format of the texture is passed in. The format parameter is only needed when overriding this behavior.

More information:

Parameters

unit (int) – Specifies the index of the image unit to which to bind the texture
texture (moderngl.Texture) – The texture to bind

Keyword Arguments

read (bool) – Allows the shader to read the image (default: True)
write (bool) – Allows the shader to write to the image (default: True)
level (int) – Level of the texture to bind (default: 0).
format (int) – (optional) The OpenGL enum value representing the format (defaults to the texture’s format)

Texture.use(location: int = 0) → None#

Bind the texture to a texture unit.

The location is the texture unit we want to bind the texture. This should correspond with the value of the sampler2D uniform in the shader because samplers read from the texture unit we assign to them:

# Define what texture unit our two sampler2D uniforms should represent
program['texture_a'] = 0
program['texture_b'] = 1
# Bind textures to the texture units
first_texture.use(location=0)
second_texture.use(location=1)

Parameters: location (int) – The texture location/unit.

Texture.release() → None#: Release the ModernGL object.

Attributes#

Texture.repeat_x: bool#

The x repeat flag for the texture (Default True).

Example:

# Enable texture repeat (GL_REPEAT)
texture.repeat_x = True

# Disable texture repeat (GL_CLAMP_TO_EDGE)
texture.repeat_x = False

Type: bool

Texture.repeat_y: bool#

The y repeat flag for the texture (Default True).

Example:

# Enable texture repeat (GL_REPEAT)
texture.repeat_y = True

# Disable texture repeat (GL_CLAMP_TO_EDGE)
texture.repeat_y = False

Type: bool

Texture.filter: Tuple[int, int]#

The minification and magnification filter for the texture.

(Default (moderngl.LINEAR. moderngl.LINEAR))

Example:

texture.filter == (moderngl.NEAREST, moderngl.NEAREST)
texture.filter == (moderngl.LINEAR_MIPMAP_LINEAR, moderngl.LINEAR)
texture.filter == (moderngl.NEAREST_MIPMAP_LINEAR, moderngl.NEAREST)
texture.filter == (moderngl.LINEAR_MIPMAP_NEAREST, moderngl.NEAREST)

Type: tuple

Texture.swizzle: str#

The swizzle mask of the texture (Default 'RGBA').

The swizzle mask change/reorder the vec4 value returned by the texture() function in a GLSL shaders. This is represented by a 4 character string were each character can be:

'R' GL_RED
'G' GL_GREEN
'B' GL_BLUE
'A' GL_ALPHA
'0' GL_ZERO
'1' GL_ONE

Example:

# Alpha channel will always return 1.0
texture.swizzle = 'RGB1'

# Only return the red component. The rest is masked to 0.0
texture.swizzle = 'R000'

# Reverse the components
texture.swizzle = 'ABGR'

Type: str

Texture.compare_func: str#

The compare function of the depth texture (Default '<=').

By default depth textures have GL_TEXTURE_COMPARE_MODE set to GL_COMPARE_REF_TO_TEXTURE, meaning any texture lookup will return a depth comparison value.

If you need to read the actual depth value in shaders, setting compare_func to a blank string will set GL_TEXTURE_COMPARE_MODE to GL_NONE making you able to read the depth texture as a sampler2D:

uniform sampler2D depth;
out vec4 fragColor;
in vec2 uv;

void main() {
    float raw_depth_nonlinear = texture(depth, uv);
    fragColor = vec4(raw_depth_nonlinear);
}

Accepted compare functions:

texture.compare_func = ''    # Disable depth comparison completely
texture.compare_func = '<='  # GL_LEQUAL
texture.compare_func = '<'   # GL_LESS
texture.compare_func = '>='  # GL_GEQUAL
texture.compare_func = '>'   # GL_GREATER
texture.compare_func = '=='  # GL_EQUAL
texture.compare_func = '!='  # GL_NOTEQUAL
texture.compare_func = '0'   # GL_NEVER
texture.compare_func = '1'   # GL_ALWAYS

Type: tuple

Texture.anisotropy: float#

Number of samples for anisotropic filtering (Default 1.0).

The value will be clamped in range 1.0 and ctx.max_anisotropy.

Any value greater than 1.0 counts as a use of anisotropic filtering:

# Disable anisotropic filtering
texture.anisotropy = 1.0

# Enable anisotropic filtering suggesting 16 samples as a maximum
texture.anisotropy = 16.0

Type: float

Texture.width: int#

The width of the texture.

Type: int

Texture.height: int#

The height of the texture.

Type: int

Texture.size: tuple#

The size of the texture.

Type: tuple

Texture.dtype: str#

Data type.

Type: str

Texture.components: int#

The number of components of the texture.

Type: int

Texture.samples: int#

The number of samples set for the texture used in multisampling.

Type: int

Texture.depth: bool#

Is the texture a depth texture?.

Type: bool

Texture.glo: int#

The internal OpenGL object.

This values is provided for debug purposes only.

Type: int

Texture.mglo: Any#: Internal representation for debug purposes only.

Texture.extra: Any#: Any - Attribute for storing user defined objects

Texture.ctx: moderngl.Context#: The context this object belongs to

TextureArray#

class moderngl.TextureArray#

An Array Texture is a Texture where each mipmap level contains an array of images of the same size.

Array textures may have Mipmaps, but each mipmap in the texture has the same number of levels.

A TextureArray object cannot be instantiated directly, it requires a context. Use Context.texture_array() to create one.

Create#

Context.texture_array(size: Tuple[int, int, int], components: int, data: Optional[Any] = None, *, alignment: int = 1, dtype: str = 'f1') → moderngl.TextureArray

Create a TextureArray object.

Parameters

size (tuple) – The (width, height, layers) of the texture.
components (int) – The number of components 1, 2, 3 or 4.
data (bytes) – Content of the texture. The size must be (width, height * layers) so each layer is stacked vertically.

Keyword Arguments

alignment (int) – The byte alignment 1, 2, 4 or 8.
dtype (str) – Data type.

Returns

Texture3D object

Methods#

TextureArray.read(*, alignment: int = 1) → bytes#

Read the pixel data as bytes into system memory.

Keyword Arguments: alignment (int) – The byte alignment of the pixels.
Returns: bytes

TextureArray.read_into(buffer: Any, *, alignment: int = 1, write_offset: int = 0) → None#

Read the content of the texture array into a bytearray or Buffer.

The advantage of reading into a Buffer is that pixel data does not need to travel all the way to system memory:

# Reading pixel data into a bytearray
data = bytearray(8)
texture = ctx.texture((2, 2, 2), 1)
texture.read_into(data)

# Reading pixel data into a buffer
data = ctx.buffer(reserve=8)
texture = ctx.texture((2, 2, 2), 1)
texture.read_into(data)

Parameters

buffer (Union[bytearray, Buffer]) – The buffer that will receive the pixels.

Keyword Arguments

alignment (int) – The byte alignment of the pixels.
write_offset (int) – The write offset.

TextureArray.write(data: Any, viewport: Optional[Union[Tuple[int, int, int], Tuple[int, int, int, int, int, int]]] = None, *, alignment: int = 1) → None#

Update the content of the texture array from byte data or a moderngl Buffer.

The viewport can be used for finer control of where the data should be written in the array. The valid versions are:

# Writing multiple layers from the begining of the texture
texture.write(data, viewport=(width, hight, num_layers))

# Writing sub-sections of the array
texture.write(data, viewport=(x, y, layer, width, height, num_layers))

Like with other texture types we can also use bytes or Buffer as a source:

# Using a moderngl buffer
data = ctx.buffer(reserve=8)
texture = ctx.texture_array((2, 2, 2), 1)
texture.write(data)

# Using byte data from system memory
data = b'\xff\xff\xff\xff\xff\xff\xff\xff'
texture = ctx.texture_array((2, 2, 2), 1)
texture.write(data)

Parameters

data (bytes) – The pixel data.
viewport (tuple) – The viewport.

Keyword Arguments

alignment (int) – The byte alignment of the pixels.

TextureArray.bind_to_image(unit: int, read: bool = True, write: bool = True, level: int = 0, format: int = 0) → None#

Bind a texture to an image unit (OpenGL 4.2 required).

It’s important to specify the right access type for the image. This can be set with the read and write arguments. Allowed combinations are:

Read-only: read=True and write=False
Write-only: read=False and write=True
Read-write: read=True and write=True

Note that we bind the texture array as layered to make all the layers accessible. This can be updated to map single layers in the future.

More information:

Parameters

unit (int) – Specifies the index of the image unit to which to bind the texture
texture (moderngl.Texture) – The texture to bind

Keyword Arguments

read (bool) – Allows the shader to read the image (default: True)
write (bool) – Allows the shader to write to the image (default: True)
level (int) – Level of the texture to bind (default: 0).
format (int) – (optional) The OpenGL enum value representing the format (defaults to the texture’s format)

TextureArray.build_mipmaps(base: int = 0, max_level: int = 1000) → None#

Generate mipmaps.

This also changes the texture filter to LINEAR_MIPMAP_LINEAR, LINEAR (Will be removed in 6.x)

Keyword Arguments

base (int) – The base level
max_level (int) – The maximum levels to generate

TextureArray.use(location: int = 0) → None#

Bind the texture to a texture unit.

The location is the texture unit we want to bind the texture. This should correspond with the value of the sampler2DArray uniform in the shader because samplers read from the texture unit we assign to them:

# Define what texture unit our two sampler2DArray uniforms should represent
program['texture_a'] = 0
program['texture_b'] = 1
# Bind textures to the texture units
first_texture.use(location=0)
second_texture.use(location=1)

Parameters: location (int) – The texture location/unit.

TextureArray.release() → None#: Release the ModernGL object.

Attributes#

TextureArray.repeat_x: bool#

The x repeat flag for the texture (Default True).

Example:

# Enable texture repeat (GL_REPEAT)
texture.repeat_x = True

# Disable texture repeat (GL_CLAMP_TO_EDGE)
texture.repeat_x = False

Type: bool

TextureArray.repeat_y: bool#

The y repeat flag for the texture (Default True).

Example:

# Enable texture repeat (GL_REPEAT)
texture.repeat_y = True

# Disable texture repeat (GL_CLAMP_TO_EDGE)
texture.repeat_y = False

Type: bool

TextureArray.filter: Tuple[int, int]#

The minification and magnification filter for the texture.

(Default (moderngl.LINEAR. moderngl.LINEAR))

Example:

texture.filter == (moderngl.NEAREST, moderngl.NEAREST)
texture.filter == (moderngl.LINEAR_MIPMAP_LINEAR, moderngl.LINEAR)
texture.filter == (moderngl.NEAREST_MIPMAP_LINEAR, moderngl.NEAREST)
texture.filter == (moderngl.LINEAR_MIPMAP_NEAREST, moderngl.NEAREST)

Type: tuple

TextureArray.swizzle: str#

The swizzle mask of the texture (Default 'RGBA').

The swizzle mask change/reorder the vec4 value returned by the texture() function in a GLSL shaders. This is represented by a 4 character string were each character can be:

'R' GL_RED
'G' GL_GREEN
'B' GL_BLUE
'A' GL_ALPHA
'0' GL_ZERO
'1' GL_ONE

Example:

# Alpha channel will always return 1.0
texture.swizzle = 'RGB1'

# Only return the red component. The rest is masked to 0.0
texture.swizzle = 'R000'

# Reverse the components
texture.swizzle = 'ABGR'

Type: str

TextureArray.anisotropy: float#

Number of samples for anisotropic filtering (Default 1.0).

The value will be clamped in range 1.0 and ctx.max_anisotropy.

Any value greater than 1.0 counts as a use of anisotropic filtering:

# Disable anisotropic filtering
texture.anisotropy = 1.0

# Enable anisotropic filtering suggesting 16 samples as a maximum
texture.anisotropy = 16.0

Type: float

TextureArray.width: int#

The width of the texture array.

Type: int

TextureArray.height: int#

The height of the texture array.

Type: int

TextureArray.layers: int#

The number of layers of the texture array.

Type: int

TextureArray.size: tuple#

The size of the texture array.

Type: tuple

TextureArray.dtype: str#

Data type.

Type: str

TextureArray.components: int#

The number of components of the texture array.

Type: int

TextureArray.glo: int#

The internal OpenGL object.

This values is provided for debug purposes only.

Type: int

TextureArray.mglo: Any#: Internal representation for debug purposes only.

TextureArray.extra: Any#: Any - Attribute for storing user defined objects

TextureArray.ctx: moderngl.Context#: The context this object belongs to

Texture3D#

class moderngl.Texture3D#

A Texture is an OpenGL object that contains one or more images that all have the same image format.

A texture can be used in two ways. It can be the source of a texture access from a Shader, or it can be used as a render target.

A Texture3D object cannot be instantiated directly, it requires a context. Use Context.texture3d() to create one.

Create#

Context.texture3d(size: Tuple[int, int, int], components: int, data: Optional[Any] = None, *, alignment: int = 1, dtype: str = 'f1') → moderngl.Texture3D

Create a Texture3D object.

Parameters

size (tuple) – The width, height and depth of the texture.
components (int) – The number of components 1, 2, 3 or 4.
data (bytes) – Content of the texture.

Keyword Arguments

alignment (int) – The byte alignment 1, 2, 4 or 8.
dtype (str) – Data type.

Returns

Texture3D object

Methods#

Texture3D.read(*, alignment: int = 1) → bytes#

Read the pixel data as bytes into system memory.

Keyword Arguments: alignment (int) – The byte alignment of the pixels.
Returns: bytes

Texture3D.read_into(buffer: Any, *, alignment: int = 1, write_offset: int = 0) → None#

Read the content of the texture into a bytearray or Buffer.

The advantage of reading into a Buffer is that pixel data does not need to travel all the way to system memory:

# Reading pixel data into a bytearray
data = bytearray(8)
texture = ctx.texture3d((2, 2, 2), 1)
texture.read_into(data)

# Reading pixel data into a buffer
data = ctx.buffer(reserve=8)
texture = ctx.texture3d((2, 2, 2), 1)
texture.read_into(data)

Parameters

buffer (Union[bytearray, Buffer]) – The buffer that will receive the pixels.

Keyword Arguments

alignment (int) – The byte alignment of the pixels.
write_offset (int) – The write offset.

Texture3D.write(data: Any, viewport: Optional[Union[Tuple[int, int, int], Tuple[int, int, int, int, int, int]]] = None, *, alignment: int = 1) → None#

Update the content of the texture from byte data or a moderngl Buffer.

Examples:

# Write data from a moderngl Buffer
data = ctx.buffer(reserve=8)
texture = ctx.texture3d((2, 2, 2), 1)
texture.write(data)

# Write data from bytes
data = b'\xff\xff\xff\xff\xff\xff\xff\xff'
texture = ctx.texture3d((2, 2), 1)
texture.write(data)

Parameters

data (bytes) – The pixel data.
viewport (tuple) – The viewport.

Keyword Arguments

alignment (int) – The byte alignment of the pixels.

Texture3D.build_mipmaps(base: int = 0, max_level: int = 1000) → None#

Generate mipmaps.

This also changes the texture filter to LINEAR_MIPMAP_LINEAR, LINEAR (Will be removed in 6.x)

Keyword Arguments

base (int) – The base level
max_level (int) – The maximum levels to generate

Texture3D.bind_to_image(unit: int, read: bool = True, write: bool = True, level: int = 0, format: int = 0) → None#

Bind a texture to an image unit (OpenGL 4.2 required).

It’s important to specify the right access type for the image. This can be set with the read and write arguments. Allowed combinations are:

Read-only: read=True and write=False
Write-only: read=False and write=True
Read-write: read=True and write=True

Note that we bind the 3D textured layered making the entire texture readable and writable. It is possible to bind a specific 2D section in the future.

More information:

Parameters

unit (int) – Specifies the index of the image unit to which to bind the texture
texture (moderngl.Texture) – The texture to bind

Keyword Arguments

read (bool) – Allows the shader to read the image (default: True)
write (bool) – Allows the shader to write to the image (default: True)
level (int) – Level of the texture to bind (default: 0).
format (int) – (optional) The OpenGL enum value representing the format (defaults to the texture’s format)

Texture3D.use(location: int = 0) → None#

Bind the texture to a texture unit.

The location is the texture unit we want to bind the texture. This should correspond with the value of the sampler3D uniform in the shader because samplers read from the texture unit we assign to them:

# Define what texture unit our two sampler3D uniforms should represent
program['texture_a'] = 0
program['texture_b'] = 1
# Bind textures to the texture units
first_texture.use(location=0)
second_texture.use(location=1)

Parameters: location (int) – The texture location/unit.

Texture3D.release() → None#: Release the ModernGL object.

Attributes#

Texture3D.repeat_x: bool#

The x repeat flag for the texture (Default True).

Example:

# Enable texture repeat (GL_REPEAT)
texture.repeat_x = True

# Disable texture repeat (GL_CLAMP_TO_EDGE)
texture.repeat_x = False

Type: bool

Texture3D.repeat_y: bool#

The y repeat flag for the texture (Default True).

Example:

# Enable texture repeat (GL_REPEAT)
texture.repeat_y = True

# Disable texture repeat (GL_CLAMP_TO_EDGE)
texture.repeat_y = False

Type: bool

Texture3D.repeat_z: bool#

The z repeat flag for the texture (Default True).

Example:

# Enable texture repeat (GL_REPEAT)
texture.repeat_z = True

# Disable texture repeat (GL_CLAMP_TO_EDGE)
texture.repeat_z = False

Type: bool

Texture3D.filter: Tuple[int, int]#

The filter of the texture.

Type: tuple

Texture3D.swizzle: str#

The swizzle mask of the texture (Default 'RGBA').

The swizzle mask change/reorder the vec4 value returned by the texture() function in a GLSL shaders. This is represented by a 4 character string were each character can be:

'R' GL_RED
'G' GL_GREEN
'B' GL_BLUE
'A' GL_ALPHA
'0' GL_ZERO
'1' GL_ONE

Example:

# Alpha channel will always return 1.0
texture.swizzle = 'RGB1'

# Only return the red component. The rest is masked to 0.0
texture.swizzle = 'R000'

# Reverse the components
texture.swizzle = 'ABGR'

Type: str

Texture3D.width: int#

The width of the texture.

Type: int

Texture3D.height: int#

The height of the texture.

Type: int

Texture3D.depth: int#

The depth of the texture.

Type: int

Texture3D.size: tuple#

The size of the texture.

Type: tuple

Texture3D.dtype: str#

Data type.

Type: str

Texture3D.components: int#

The number of components of the texture.

Type: int

Texture3D.glo: int#

The internal OpenGL object.

This values is provided for debug purposes only.

Type: int

Texture3D.mglo: Any#: Internal representation for debug purposes only.

Texture3D.extra: Any#: Any - Attribute for storing user defined objects

Texture3D.ctx: moderngl.Context#: The context this object belongs to

TextureCube#

class moderngl.TextureCube#

Cubemaps are a texture using the type GL_TEXTURE_CUBE_MAP.

They are similar to 2D textures in that they have two dimensions. However, each mipmap level has 6 faces, with each face having the same size as the other faces.

The width and height of a cubemap must be the same (ie: cubemaps are squares), but these sizes need not be powers of two.

Note

ModernGL enables GL_TEXTURE_CUBE_MAP_SEAMLESS globally to ensure filtering will be done across the cube faces.

A Texture3D object cannot be instantiated directly, it requires a context. Use Context.texture_cube() to create one.

Create#

Create a TextureCube object.

Note that the width and height of the cubemap must be the same unless you are using a non-standard extension.

Parameters

size (tuple) – The width, height of the texture. Each side of the cube will have this size.
components (int) – The number of components 1, 2, 3 or 4.
data (bytes) – Content of the texture. The data should be have the following ordering: positive_x, negative_x, positive_y, negative_y, positive_z, negative_z

Keyword Arguments

alignment (int) – The byte alignment 1, 2, 4 or 8.
dtype (str) – Data type.
internal_format (int) – Override the internalformat of the texture (IF needed)

Returns

TextureCube object

Methods#

TextureCube.read(face: int, *, alignment: int = 1) → bytes#

Read a face from the cubemap as bytes into system memory.

Face values are:

Positive X
Negative X
Positive Y
Negative Y
Positive Z
Negative Z

Parameters: face (int) – The face to read.
Keyword Arguments: alignment (int) – The byte alignment of the pixels.

TextureCube.read_into(buffer: Any, face: int, *, alignment: int = 1, write_offset: int = 0) → None#

Read a face from the cubemap texture.

Read a face of the cubemap into a bytearray or Buffer. The advantage of reading into a Buffer is that pixel data does not need to travel all the way to system memory:

# Reading pixel data into a bytearray
data = bytearray(4)
texture = ctx.texture_cube((2, 2), 1)
texture.read_into(data, 0)

# Reading pixel data into a buffer
data = ctx.buffer(reserve=4)
texture = ctx.texture_cube((2, 2), 1)
texture.read_into(data, 0)

Parameters

buffer (bytearray) – The buffer that will receive the pixels.
face (int) – The face to read.

Keyword Arguments

alignment (int) – The byte alignment of the pixels.
write_offset (int) – The write offset.

TextureCube.write(face: int, data: Any, viewport: Optional[Union[Tuple[int, int], Tuple[int, int, int, int]]] = None, *, alignment: int = 1) → None#

Update the content of the texture.

Update the content of a face in the cubemap from byte data or a moderngl Buffer:

# Write data from a moderngl Buffer
data = ctx.buffer(reserve=4)
texture = ctx.texture_cube((2, 2), 1)
texture.write(0, data)

# Write data from bytes
data = b'\xff\xff\xff\xff'
texture = ctx.texture_cube((2, 2), 1)
texture.write(0, data)

Parameters

face (int) – The face to update.
data (bytes) – The pixel data.
viewport (tuple) – The viewport.

Keyword Arguments

alignment (int) – The byte alignment of the pixels.

TextureCube.bind_to_image(unit: int, read: bool = True, write: bool = True, level: int = 0, format: int = 0) → None#

Bind a texture to an image unit (OpenGL 4.2 required).

It’s important to specify the right access type for the image. This can be set with the read and write arguments. Allowed combinations are:

Read-only: read=True and write=False
Write-only: read=False and write=True
Read-write: read=True and write=True

Note that we bind the texture cube as layered to make all the faces accessible. This can be updated to map single faces in the future. The Z component in imageLoad/Store represents the face id we are writing to (0-5).

More information:

Parameters

unit (int) – Specifies the index of the image unit to which to bind the texture
texture (moderngl.Texture) – The texture to bind

Keyword Arguments

read (bool) – Allows the shader to read the image (default: True)
write (bool) – Allows the shader to write to the image (default: True)
level (int) – Level of the texture to bind (default: 0).
format (int) – (optional) The OpenGL enum value representing the format (defaults to the texture’s format)

TextureCube.use(location: int = 0) → None#

Bind the texture to a texture unit.

The location is the texture unit we want to bind the texture. This should correspond with the value of the samplerCube uniform in the shader because samplers read from the texture unit we assign to them:

# Define what texture unit our two samplerCube uniforms should represent
program['texture_a'] = 0
program['texture_b'] = 1
# Bind textures to the texture units
first_texture.use(location=0)
second_texture.use(location=1)

Parameters: location (int) – The texture location/unit.

TextureCube.release() → None#: Release the ModernGL object.

Attributes#

TextureCube.size: Tuple[int, int]#

The size of the texture cube (single face).

Type: tuple

TextureCube.dtype: str#

Data type.

Type: str

TextureCube.components: int#

The number of components of the texture.

Type: int

TextureCube.filter: Tuple[int, int]#

The minification and magnification filter for the texture.

(Default (moderngl.LINEAR. moderngl.LINEAR))

Example:

texture.filter == (moderngl.NEAREST, moderngl.NEAREST)
texture.filter == (moderngl.LINEAR_MIPMAP_LINEAR, moderngl.LINEAR)
texture.filter == (moderngl.NEAREST_MIPMAP_LINEAR, moderngl.NEAREST)
texture.filter == (moderngl.LINEAR_MIPMAP_NEAREST, moderngl.NEAREST)

Type: tuple

TextureCube.swizzle: str#

The swizzle mask of the texture (Default 'RGBA').

The swizzle mask change/reorder the vec4 value returned by the texture() function in a GLSL shaders. This is represented by a 4 character string were each character can be:

'R' GL_RED
'G' GL_GREEN
'B' GL_BLUE
'A' GL_ALPHA
'0' GL_ZERO
'1' GL_ONE

Example:

# Alpha channel will always return 1.0
texture.swizzle = 'RGB1'

# Only return the red component. The rest is masked to 0.0
texture.swizzle = 'R000'

# Reverse the components
texture.swizzle = 'ABGR'

Type: str

TextureCube.anisotropy: float#

Number of samples for anisotropic filtering (Default 1.0).

The value will be clamped in range 1.0 and ctx.max_anisotropy.

Any value greater than 1.0 counts as a use of anisotropic filtering:

# Disable anisotropic filtering
texture.anisotropy = 1.0

# Enable anisotropic filtering suggesting 16 samples as a maximum
texture.anisotropy = 16.0

Type: float

TextureCube.glo: int#

The internal OpenGL object.

This values is provided for debug purposes only.

Type: int

TextureCube.mglo: Any#: Internal representation for debug purposes only.

TextureCube.extra: Any#: Any - Attribute for storing user defined objects

TextureCube.ctx: moderngl.Context#: The context this object belongs to

Framebuffer#

class moderngl.Framebuffer#

A Framebuffer is a collection of buffers that can be used as the destination for rendering.

The buffers for Framebuffer objects reference images from either Textures or Renderbuffers. Create a Framebuffer using Context.framebuffer().

Create#

Context.simple_framebuffer(size: Tuple[int, int], components: int = 4, *, samples: int = 0, dtype: str = 'f1') → moderngl.Framebuffer

Creates a Framebuffer with a single color attachment and depth buffer using moderngl.Renderbuffer attachments.

Parameters

size (tuple) – The width and height of the renderbuffer.
components (int) – The number of components 1, 2, 3 or 4.

Keyword Arguments

samples (int) – The number of samples. Value 0 means no multisample format.
dtype (str) – Data type.

Returns

Framebuffer object

Context.framebuffer(color_attachments: Any = (), depth_attachment: Optional[Union[moderngl.Texture, moderngl.Renderbuffer]] = None) → moderngl.Framebuffer

A Framebuffer is a collection of buffers that can be used as the destination for rendering. The buffers for Framebuffer objects reference images from either Textures or Renderbuffers.

Parameters

color_attachments (list) – A list of Texture or Renderbuffer objects.
depth_attachment (Renderbuffer or Texture) – The depth attachment.

Returns

Framebuffer object

Methods#

Framebuffer.clear(red: float = 0.0, green: float = 0.0, blue: float = 0.0, alpha: float = 0.0, depth: float = 1.0, *, viewport: Optional[Union[Tuple[int, int], Tuple[int, int, int, int]]] = None, color: Optional[Tuple[float, float, float, float]] = None) → None#

Clear the framebuffer.

If a viewport passed in, a scissor test will be used to clear the given viewport. This viewport take presence over the framebuffers scissor. Clearing can still be done with scissor if no viewport is passed in.

This method also respects the color_mask and depth_mask. It can for example be used to only clear the depth or color buffer or specific components in the color buffer.

If the viewport is a 2-tuple it will clear the (0, 0, width, height) where (width, height) is the 2-tuple.

If the viewport is a 4-tuple it will clear the given viewport.

Parameters

red (float) – color component.
green (float) – color component.
blue (float) – color component.
alpha (float) – alpha component.
depth (float) – depth value.

Keyword Arguments

viewport (tuple) – The viewport.
color (tuple) – Optional tuple replacing the red, green, blue and alpha arguments

Framebuffer.read(viewport: Optional[Union[Tuple[int, int], Tuple[int, int, int, int]]] = None, components: int = 3, *, attachment: int = 0, alignment: int = 1, dtype: str = 'f1', clamp: bool = False) → bytes#

Read the content of the framebuffer.

# Read the first color attachment's RGBA data
data = fbo.read(components=4)
# Read the second color attachment's RGB data
data = fbo.read(attachment=1)
# Read the depth attachment
data = fbo.read(attachment=-1)
# Read the lower left 10 x 10 pixels from the first color attachment
data = fbo.read(viewport=(0, 0, 10, 10))

Parameters

viewport (tuple) – The viewport.
components (int) – The number of components to read.

Keyword Arguments

attachment (int) – The color attachment number. -1 for the depth attachment
alignment (int) – The byte alignment of the pixels.
dtype (str) – Data type.
clamp (bool) – Clamps floating point values to [0.0, 1.0]

Returns

bytes

Framebuffer.read_into(buffer: Any, viewport: Optional[Union[Tuple[int, int], Tuple[int, int, int, int]]] = None, components: int = 3, *, attachment: int = 0, alignment: int = 1, dtype: str = 'f1', write_offset: int = 0) → None#

Read the content of the framebuffer into a buffer.

Parameters

buffer (bytearray) – The buffer that will receive the pixels.
viewport (tuple) – The viewport.
components (int) – The number of components to read.

Keyword Arguments

attachment (int) – The color attachment.
alignment (int) – The byte alignment of the pixels.
dtype (str) – Data type.
write_offset (int) – The write offset.

Framebuffer.use() → None#: Bind the framebuffer. Sets the target for rendering commands.

Framebuffer.release() → None#: Release the ModernGL object.

Attributes#

Framebuffer.viewport: Tuple[int, int, int, int]#

Get or set the viewport of the framebuffer.

Type: tuple

Framebuffer.scissor: Tuple[int, int, int, int]#

Get or set the scissor box of the framebuffer.

When scissor testing is enabled fragments outside the defined scissor box will be discarded. This applies to rendered geometry or Framebuffer.clear().

Setting is value enables scissor testing in the framebuffer. Setting the scissor to None disables scissor testing and reverts the scissor box to match the framebuffer size.

Example:

# Enable scissor testing
>>> ctx.scissor = 100, 100, 200, 100
# Disable scissor testing
>>> ctx.scissor = None

Type: tuple

Framebuffer.color_mask: Tuple[bool, bool, bool, bool]#

The color mask of the framebuffer.

Color masking controls what components in color attachments will be affected by fragment write operations. This includes rendering geometry and clearing the framebuffer.

Default value: (True, True, True, True).

Examples:

# Block writing to all color components (rgba) in color attachments
fbo.color_mask = False, False, False, False

# Re-enable writing to color attachments
fbo.color_mask = True, True, True, True

# Block fragment writes to alpha channel
fbo.color_mask = True, True, True, False

Type: tuple

Framebuffer.depth_mask: bool#

The depth mask of the framebuffer.

Depth mask enables or disables write operations to the depth buffer. This also applies when clearing the framebuffer. If depth testing is enabled fragments will still be culled, but the depth buffer will not be updated with new values. This is a very useful tool in many rendering techniques.

Default value: True

Type: bool

Framebuffer.width: int#

The width of the framebuffer.

Framebuffers created by a window will only report its initial size. It’s better get size information from the window itself.

Type: int

Framebuffer.height: int#

The height of the framebuffer.

Framebuffers created by a window will only report its initial size. It’s better get size information from the window itself.

Type: int

Framebuffer.size: Tuple[int, int]#

The size of the framebuffer.

Framebuffers created by a window will only report its initial size. It’s better get size information from the window itself.

Type: Tuple[int, int]

Framebuffer.samples: int#

The samples of the framebuffer.

Type: int

Framebuffer.bits: Dict[str, str]#

The bits of the framebuffer.

Type: dict

Framebuffer.color_attachments: Tuple[Union[moderngl.Texture, moderngl.Renderbuffer], ...]#

The color attachments of the framebuffer.

Type: tuple

Framebuffer.depth_attachment: Union[moderngl.Texture, moderngl.Renderbuffer]#

The depth attachment of the framebuffer.

Type: Texture or Renderbuffer

Framebuffer.glo: int#

The internal OpenGL object.

This values is provided for debug purposes only.

Type: int

Framebuffer.mglo: Any#: Internal representation for debug purposes only.

Framebuffer.extra: Any#: Any - Attribute for storing user defined objects

Framebuffer.ctx: moderngl.Context#: The context this object belongs to

Renderbuffer#

class moderngl.Renderbuffer#

Renderbuffer objects are OpenGL objects that contain images.

They are created and used specifically with Framebuffer objects. They are optimized for use as render targets, while Texture objects may not be, and are the logical choice when you do not need to sample from the produced image. If you need to resample, use Textures instead. Renderbuffer objects also natively accommodate multisampling.

A Renderbuffer object cannot be instantiated directly, it requires a context. Use Context.renderbuffer() or Context.depth_renderbuffer() to create one.

Create#

Context.renderbuffer(size: Tuple[int, int], components: int = 4, *, samples: int = 0, dtype: str = 'f1') → moderngl.Renderbuffer

Renderbuffer objects are OpenGL objects that contain images. They are created and used specifically with Framebuffer objects.

Parameters

size (tuple) – The width and height of the renderbuffer.
components (int) – The number of components 1, 2, 3 or 4.

Keyword Arguments

samples (int) – The number of samples. Value 0 means no multisample format.
dtype (str) – Data type.

Returns

Renderbuffer object

Context.depth_renderbuffer(size: Tuple[int, int], *, samples: int = 0) → moderngl.Renderbuffer

Renderbuffer objects are OpenGL objects that contain images. They are created and used specifically with Framebuffer objects.

Parameters: size (tuple) – The width and height of the renderbuffer.
Keyword Arguments: samples (int) – The number of samples. Value 0 means no multisample format.
Returns: Renderbuffer object

Methods#

Renderbuffer.release() → None#: Release the ModernGL object.

Attributes#

Renderbuffer.width: int#

The width of the renderbuffer.

Type: int

Renderbuffer.height: int#

The height of the renderbuffer.

Type: int

Renderbuffer.size: tuple#

The size of the renderbuffer.

Type: tuple

Renderbuffer.samples: int#

The samples of the renderbuffer.

Type: int

Renderbuffer.components: int#

The components of the renderbuffer.

Type: int

Renderbuffer.depth: bool#

Is the renderbuffer a depth renderbuffer?.

Type: bool

Renderbuffer.dtype: str#

Data type.

Type: str

Renderbuffer.glo: int#

The internal OpenGL object.

This values is provided for debug purposes only.

Type: int

Renderbuffer.mglo: Any#: Internal representation for debug purposes only.

Renderbuffer.extra: Any#: Any - Attribute for storing user defined objects

Renderbuffer.ctx: moderngl.Context#: The context this object belongs to

Scope#

class moderngl.Scope#

This class represents a Scope object.

Responsibilities on enter:

Set the enable flags.
Bind the framebuffer.
Assigning textures to texture locations.
Assigning buffers to uniform buffers.
Assigning buffers to shader storage buffers.

Responsibilities on exit:

Restore the enable flags.
Restore the framebuffer.

Create#

Create a Scope object.

Parameters

framebuffer (Framebuffer) – The framebuffer to use when entering.
enable_only (int) – The enable_only flags to set when entering.

Keyword Arguments

textures (tuple) – List of (texture, binding) tuples.
uniform_buffers (tuple) – Tuple of (buffer, binding) tuples.
storage_buffers (tuple) – Tuple of (buffer, binding) tuples.
samplers (tuple) – Tuple of sampler bindings
enable (int) – Flags to enable for this vao such as depth testing and blending

Methods#

Scope.__enter__()#

Scope.__exit__(*args: Tuple[Any])#

Scope.release() → None#: Destroy the Scope object.

Attributes#

Scope.extra: Any#: Any - Attribute for storing user defined objects

Scope.mglo: Any#: Internal representation for debug purposes only.

Scope.ctx: moderngl.Context#: The context this object belongs to

Examples#

Simple scope example

scope1 = ctx.scope(fbo1, moderngl.BLEND)
scope2 = ctx.scope(fbo2, moderngl.DEPTH_TEST | moderngl.CULL_FACE)

with scope1:
    # do some rendering

with scope2:
    # do some rendering

Scope for querying

query = ctx.query(samples=True)
scope = ctx.scope(ctx.screen, moderngl.DEPTH_TEST | moderngl.RASTERIZER_DISCARD)

with scope, query:
    # do some rendering

print(query.samples)

Understanding what scope objects do

scope = ctx.scope(
    framebuffer=framebuffer1,
    enable_only=moderngl.BLEND,
    textures=[
        (texture1, 4),
        (texture2, 3),
    ],
    uniform_buffers=[
        (buffer1, 6),
        (buffer2, 5),
    ],
    storage_buffers=[
        (buffer3, 8),
    ],
)

# Let's assume we have some state before entering the scope
some_random_framebuffer.use()
some_random_texture.use(3)
some_random_buffer.bind_to_uniform_block(5)
some_random_buffer.bind_to_storage_buffer(8)
ctx.enable_only(moderngl.DEPTH_TEST)

with scope:
    # on __enter__
    #     framebuffer1.use()
    #     ctx.enable_only(moderngl.BLEND)
    #     texture1.use(4)
    #     texture2.use(3)
    #     buffer1.bind_to_uniform_block(6)
    #     buffer2.bind_to_uniform_block(5)
    #     buffer3.bind_to_storage_buffer(8)

    # do some rendering

    # on __exit__
    #     some_random_framebuffer.use()
    #     ctx.enable_only(moderngl.DEPTH_TEST)

# Originally we had the following, let's see what was changed
some_random_framebuffer.use()                 # This was restored hurray!
some_random_texture.use(3)                    # Have to restore it manually.
some_random_buffer.bind_to_uniform_block(5)   # Have to restore it manually.
some_random_buffer.bind_to_storage_buffer(8)  # Have to restore it manually.
ctx.enable_only(moderngl.DEPTH_TEST)          # This was restored too.

# Scope objects only do as much as necessary.
# Restoring the framebuffer and enable flags are lowcost operations and
# without them you could get a hard time debugging the application.

Query#

class moderngl.Query#: This class represents a Query object.

Create#

Context.query(*, samples: bool = False, any_samples: bool = False, time: bool = False, primitives: bool = False) → moderngl.Query

Create a Query object.

Keyword Arguments

samples (bool) – Query GL_SAMPLES_PASSED or not.
any_samples (bool) – Query GL_ANY_SAMPLES_PASSED or not.
time (bool) – Query GL_TIME_ELAPSED or not.
primitives (bool) – Query GL_PRIMITIVES_GENERATED or not.

Attributes#

Query.samples: int#

The number of samples passed.

Type: int

Query.primitives: int#

The number of primitives generated.

Type: int

Query.elapsed: int#

The time elapsed in nanoseconds.

Type: int

Query.crender: Optional[moderngl.ConditionalRender]#: Can be used in a with statement.

Query.extra: Any#: Any - Attribute for storing user defined objects

Query.mglo: Any#: Internal representation for debug purposes only.

Query.ctx: moderngl.Context#: The context this object belongs to

Examples#

Simple query example

import moderngl
import numpy as np

ctx = moderngl.create_standalone_context()
prog = ctx.program(
    vertex_shader='''
        #version 330

        in vec2 in_vert;

        void main() {
            gl_Position = vec4(in_vert, 0.0, 1.0);
        }
    ''',
    fragment_shader='''
        #version 330

        out vec4 color;

        void main() {
            color = vec4(1.0, 0.0, 0.0, 1.0);
        }
    ''',
)

vertices = np.array([
    0.0, 0.0,
    1.0, 0.0,
    0.0, 1.0,
], dtype='f4')

vbo = ctx.buffer(vertices.tobytes())
vao = ctx.simple_vertex_array(prog, vbo, 'in_vert')

fbo = ctx.simple_framebuffer((64, 64))
fbo.use()

query = ctx.query(samples=True, time=True)

with query:
    vao.render()

print('It took %d nanoseconds' % query.elapsed)
print('to render %d samples' % query.samples)

Output

It took 13529 nanoseconds
to render 496 samples

ConditionalRender#

class moderngl.ConditionalRender#

This class represents a ConditionalRender object.

ConditionalRender objects can only be accessed from Query objects.

Attributes#

ConditionalRender.mglo: Any#: Internal representation for debug purposes only.

Examples#

Simple conditional rendering example

query = ctx.query(any_samples=True)

with query:
    vao1.render()

with query.crender:
    print('This will always get printed')
    vao2.render()  # But this will be rendered only if vao1 has passing samples.

ComputeShader#

class moderngl.ComputeShader#

A Compute Shader is a Shader Stage that is used entirely for computing arbitrary information.

While it can do rendering, it is generally used for tasks not directly related to drawing.

Compute shaders support uniforms are other member object just like a
moderngl.Program.
Storage buffers can be bound using Buffer.bind_to_storage_buffer().
Uniform buffers can be bound using Buffer.bind_to_uniform_block().
Images can be bound using Texture.bind_to_image().

Create#

Context.compute_shader(source: str) → moderngl.ComputeShader

A ComputeShader is a Shader Stage that is used entirely for computing arbitrary information. While it can do rendering, it is generally used for tasks not directly related to drawing.

Parameters: source (str) – The source of the compute shader.
Returns: ComputeShader object

Methods#

ComputeShader.run(group_x: int = 1, group_y: int = 1, group_z: int = 1) → None#

Run the compute shader.

Parameters

group_x (int) – The number of work groups to be launched in the X dimension.
group_y (int) – The number of work groups to be launched in the Y dimension.
group_z (int) – The number of work groups to be launched in the Z dimension.

ComputeShader.get(key: str, default: Any) → Union[moderngl.Uniform, moderngl.UniformBlock, moderngl.Subroutine, moderngl.Attribute, moderngl.Varying]#

Returns a Uniform, UniformBlock, Subroutine, Attribute or Varying.

Parameters: default – This is the value to be returned in case key does not exist.
Returns: Uniform, UniformBlock, Subroutine, Attribute or Varying

ComputeShader.release() → None#: Release the ModernGL object.

ComputeShader.__eq__(value, /)#: Return self==value.

ComputeShader.__getitem__(key: str) → Union[moderngl.Uniform, moderngl.UniformBlock, moderngl.Subroutine, moderngl.Attribute, moderngl.Varying]#

Get a member such as uniforms, uniform blocks, subroutines, attributes and varyings by name.

# Get a uniform
uniform = program['color']

# Uniform values can be set on the returned object
# or the `__setitem__` shortcut can be used.
program['color'].value = 1.0, 1.0, 1.0, 1.0

# Still when writing byte data we need to use the `write()` method
program['color'].write(buffer)

ComputeShader.__setitem__(key: str, value: Any)#

Set a value of uniform or uniform block.

# Set a vec4 uniform
uniform['color'] = 1.0, 1.0, 1.0, 1.0

# Optionally we can store references to a member and set the value directly
uniform = program['color']
uniform.value = 1.0, 0.0, 0.0, 0.0

uniform = program['cameraMatrix']
uniform.write(camera_matrix)

ComputeShader.__iter__() → Generator[str, None, None]#

Yields the internal members names as strings.

This includes all members such as uniforms, attributes etc.

Attributes#

ComputeShader.glo: int#

The internal OpenGL object.

This values is provided for debug purposes only.

Type: int

ComputeShader.mglo: Any#: Internal representation for debug purposes only.

ComputeShader.extra: Any#: Any - Attribute for storing user defined objects

ComputeShader.ctx: moderngl.Context#: The context this object belongs to

ModernGL#

Install#

From PyPI (pip)#

Development Environment#

Using with Mesa 3D on Windows#

Using MSYS2#

32-bit python#

64-bit python#

Using ModernGL in CI#

Windows CI Configuration#

Steps#

Example Configuration#

Linux#

Steps#

Example Configuration#

macOS#

The Guide#

An introduction to OpenGL#

The simplified story#

Beyond OpenGL#

Where do ModernGL fit into all this?#

Creating a Context#

ModernGL Types#

Shader Introduction#

Vertex Shader (transforms)#

Rendering#

Program#

VertexArray#

Topics#

The Lifecycle of a ModernGL Object#

Standalone / Headless Context#

Context Detection#

The Threading Issue#

Manually Releasing Objects#

Detecting Released Objects#

Context Creation#

Introduction#

Require a minimum OpenGL version#

Specifying context backend#

Context Sharing#

Context Info#

Texture Format#

Description#

Float Textures#

Integer Textures#

Unsigned#

Signed#

Normalized Integer Textures#

Unsigned#

Signed#

Overriding internalformat#

Buffer Format#

Description#

Syntax#

Examples#

Example buffer formats#

Example of simple usage#

Example of single interleaved array#

Example of multiple arrays with differing /usage#

Techniques#

Headless on Ubuntu 18 Server#

Dependencies#

Creating a context#

Running an example#

Reference#

moderngl#

Attributes#

Context Flags#

Primitive Modes#

Texture Filters#

Blend Functions#

Shortcuts#

Blend Equations#

Provoking Vertex#

Functions#

Context#

Create#

ModernGL Objects#

Methods#

Attributes#

Example of multiple arrays with differing `/usage`#