Context#
- class Context#
Returned by
moderngl.create_context()
Class exposing OpenGL features.
ModernGL objects can be created from this class.
Objects#
- Context.program(vertex_shader: str, fragment_shader: str, geometry_shader: str, tess_control_shader: str, tess_evaluation_shader: str, varyings: Tuple[str, ...], fragment_outputs: Dict[str, int], varyings_capture_mode: str = 'interleaved') 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 usinglayout(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.
- Context.buffer(data=None, reserve: int = 0, dynamic: bool = False) Buffer #
Returns a new
Buffer
object.The data can be anything supporting the buffer interface.
The data and reserve parameters are mutually exclusive.
- Parameters:
data (bytes) – Content of the new buffer.
reserve (int) – The number of bytes to reserve.
dynamic (bool) – Treat buffer as dynamic.
- Context.vertex_array(program: Program, content: list, index_buffer: Buffer = None, index_element_size: int = 4, mode: int = ...) VertexArray #
Returns a new
VertexArray
object.A VertexArray describes how buffers are read by a shader program. The content is a list of tuples containing a buffer, a format string and any number of attribute names. Attribute names are defined by the user in the Vertex Shader program stage.
The default mode is
TRIANGLES
.- Parameters:
program (Program) – The program used when rendering
content (list) – A list of (buffer, format, attributes). See Buffer Format.
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
)
Examples:
# Empty vertext array (no attribute input) vao = ctx.vertex_array(program) # 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 )
Backward Compatible Version:
# 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)
- Context.simple_vertex_array(...)#
Deprecated, use
Context.vertex_array()
instead.
- Context.texture(size: Tuple[int, int], components: int, data: Any = None, samples: int = 0, alignment: int = 1, dtype: str = 'f1') Texture #
Returns a new
Texture
object.A Texture is a 2D image that can be used for sampler2D uniforms or as render targets if framebuffers.
- 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.
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)
Example:
from PIL import Image img = Image.open(...).convert('RGBA') texture = ctx.texture(img.size, components=4, data=img.tobytes()) # float texture texture = ctx.texture((64, 64), components=..., dtype='f4') # integer texture texture = ctx.texture((64, 64), components=..., dtype='i4')
Note
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.
- Context.framebuffer(color_attachments: List[Texture], depth_attachment: Texture = None) Framebuffer #
Returns a new
Framebuffer
object.A Framebuffer is a collection of images that can be used as render targets. The images of the Framebuffer object can be either Textures or Renderbuffers.
- Parameters:
color_attachments (list) – A list of
Texture
orRenderbuffer
objects.depth_attachment (Texture) – The depth attachment.
- Context.sampler(repeat_x: bool, repeat_y: bool, repeat_z: bool, filter: tuple, anisotropy: float, compare_func: str, border_color: tuple, min_lod: float, max_lod: float, texture: Texture) Sampler #
Returns a new
Sampler
object.Samplers bind Textures to uniform samplers within a Program object. Binding a Sampler object also binds the texture object attached to it.
- Parameters:
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 (str) – 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.depth_texture(size: Tuple[int, int], data: Any = None, samples: int = 0, alignment: int = 4) Texture #
Returns a new
Texture
object.A depth texture can be used for sampler2D and sampler2DShadow uniforms and as a depth attachment for framebuffers.
- Parameters:
size (tuple) – The width and height of the texture.
data (bytes) – Content of the texture.
samples (int) – The number of samples. Value 0 means no multisample format.
alignment (int) – The byte alignment 1, 2, 4 or 8.
- Context.texture3d(size: Tuple[int, int, int], components: int, data: Any = None, alignment: int = 1, dtype: str = 'f1') Texture3D #
Returns a new
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.
alignment (int) – The byte alignment 1, 2, 4 or 8.
dtype (str) – Data type.
- Context.texture_array(size: Tuple[int, int, int], components: int, data: Any = None, *, alignment: int = 1, dtype: str = 'f1') TextureArray #
Returns a new
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.alignment (int) – The byte alignment 1, 2, 4 or 8.
dtype (str) – Data type.
- Context.texture_cube(size: Tuple[int, int], components: int, data: Any = None, alignment: int = 1, dtype: str = 'f1') TextureCube #
Returns a new
TextureCube
object.Note that the width and height of the cubemap must be the same.
- 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
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)
- Context.depth_texture_cube(size: Tuple[int, int], data: Any | None = None, alignment: int = 4) TextureCube #
Returns a new
TextureCube
object.- Parameters:
size (tuple) – The width and height of the texture.
data (bytes) – Content of the texture.
alignment (int) – The byte alignment 1, 2, 4 or 8.
- Context.simple_framebuffer(...)#
Deprecated, use
Context.framebuffer()
instead.
- Context.renderbuffer(size: Tuple[int, int], components: int = 4, samples: int = 0, dtype: str = 'f1') Renderbuffer #
Returns a new
Renderbuffer
object.Similar to textures, renderbuffers can be attached to framebuffers as render targets, but they cannot be sampled as textures.
- Parameters:
size (tuple) – The width and height of the renderbuffer.
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.depth_renderbuffer(size: Tuple[int, int], samples: int = 0) Renderbuffer #
Returns a new
Renderbuffer
object.- Parameters:
size (tuple) – The width and height of the renderbuffer.
samples (int) – The number of samples. Value 0 means no multisample format.
- Context.scope(framebuffer, enable_only, textures, uniform_buffers, storage_buffers, samplers)#
Returns a new
Scope
object.Scope objects can be attached to VertexArray objects to minimize the possibility of rendering within the wrong scope. VertexArrays with an attached scope always have the scope settings at render time.
- Parameters:
framebuffer (Framebuffer) – The framebuffer to use when entering.
enable_only (int) – The enable_only flags to set when entering.
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
- Context.query(samples: bool, any_samples: bool, time: bool, primitives: bool) Query #
Returns a new
Query
object.- Parameters:
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(...)#
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.
External Objects#
External objects are only useful for interoperability with other libraries.
- Context.external_texture(glo: int, size: Tuple[int, int], components: int, samples: int, dtype: str) Texture #
Returns a new
Texture
object from an existing OpenGL texture object.The content of the texture is referenced and it is not copied.
- 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.
Methods#
- Context.clear()#
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
anddepth_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.
- Args:
red (float): color component. green (float): color component. blue (float): color component. alpha (float): alpha component. depth (float): depth value.
- Keyword Args:
viewport (tuple): The viewport. color (tuple): Optional rgba color tuple
- Context.enable_only()#
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:
moderngl.NOTHING
moderngl.BLEND
moderngl.DEPTH_TEST
moderngl.CULL_FACE
moderngl.RASTERIZER_DISCARD
moderngl.PROGRAM_POINT_SIZE
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)
- Args:
flags (EnableFlag): The flags to enable
- Context.enable()#
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)
- Args:
flag (int): The flags to enable.
- Context.disable()#
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)
- Args:
flag (int): The flags to disable.
- Context.enable_direct()#
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()#
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()#
Wait for all drawing commands to finish.
- Context.clear_samplers()#
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.
- Parameters:
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.copy_buffer()#
Copy buffer content.
- Args:
dst (Buffer): The destination buffer. src (Buffer): The source buffer. size (int): The number of bytes to copy.
- Keyword Args:
read_offset (int): The read offset. write_offset (int): The write offset.
- Context.copy_framebuffer()#
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.
- Args:
dst (Framebuffer or Texture): Destination framebuffer or texture. src (Framebuffer): Source framebuffer.
- Context.detect_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.
- Args:
glo (int): Framebuffer object.
- Context.memory_barrier()#
Applying a memory barrier.
The memory barrier is needed in particular to correctly change buffers or textures between each shader. If the same buffer is changed in two shaders, it can cause an effect like ‘depth fighting’ on a buffer or texture.
The method should be used between
Program
-s, betweenComputeShader
-s, and betweenProgram
-s andComputeShader
-s.- Keyword Args:
barriers (int): Affected barriers, default moderngl.ALL_BARRIER_BITS. by_region (bool): Memory barrier mode by region. More read on https://registry.khronos.org/OpenGL-Refpages/gl4/html/glMemoryBarrier.xhtml
- Context.gc() int #
Deletes OpenGL objects. Returns the number of objects deleted.
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.
- Context.release()#
Attributes#
- Context.gc_mode: str#
The garbage collection mode.
The default mode is
None
meaning no automatic garbage collection is done. Other modes areauto
andcontext_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'
- Context.objects: deque#
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.
- 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 togl_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.
- 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
- Context.depth_clamp_range: Tuple[float, float]#
Setting up depth clamp range (write only, by default
None
).ctx.depth_clamp_range
offers uniform use of GL_DEPTH_CLAMP and glDepthRange.GL_DEPTH_CLAMP
is needed to disable clipping of fragments outside near limit of projection matrix. For example, this will allow you to draw between 0 and 1 in the Z (depth) coordinate, even ifnear
is set to 0.5 in the projection matrix.Note
All fragments outside the
near
of the projection matrix will have a depth ofnear
.See https://www.khronos.org/opengl/wiki/Vertex_Post-Processing#Depth_clamping for more info.
glDepthRange(nearVal, farVal)
is needed to specify mapping of depth values from normalized device coordinates to window coordinates. See https://registry.khronos.org/OpenGL-Refpages/gl4/html/glDepthRange.xhtml for more info.Example:
# For glDisable(GL_DEPTH_CLAMP) and glDepthRange(0, 1) ctx.depth_clamp_range = None # For glEnable(GL_DEPTH_CLAMP) and glDepthRange(near, far) ctx.depth_clamp_range = (near, far)
- Context.blend_func: tuple#
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 )
- Context.blend_equation: tuple#
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
- Context.multisample: bool#
Enable/disable multisample mode (
GL_MULTISAMPLE
).This property is write only.
Example:
# Enable ctx.multisample = True # Disable ctx.multisample = False
- Context.viewport: tuple#
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.
- Context.scissor: tuple#
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.
- Context.version_code: int#
- Context.screen: 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 framebufferid=0
.When creating a standalone context this property is not set since there are no default framebuffer.
- Context.fbo: 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'
- 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'
- Context.wireframe: bool#
Wireframe settings for debugging.
- Context.max_samples: int#
The maximum supported number of samples for multisampling.
- Context.max_integer_samples: int#
The max integer samples.
- Context.max_texture_units: int#
The max texture units.
- Context.max_anisotropy: float#
The maximum value supported for anisotropic filtering.
- Context.default_texture_unit: int#
The default texture unit.
- Context.patch_vertices: int#
The number of vertices that will be used to make up a single patch primitive.
- 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
- Context.polygon_offset: tuple#
Get or set the current polygon offset.
The tuple values represents two float values:
unit
and afactor
: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 int.
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 int offset to depth and will do the job aloneif 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 to0
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
- 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.
- Context.extensions: Set[str]#
The extensions supported by the context.
All extensions names have a
GL_
prefix, so if the spec refers toARB_compute_shader
we need to look forGL_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 .. }
- 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 }
- Context.includes: Dict[str, str]#
Mapping used for include statements.
- Context.extra: Any#
User defined data.
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: int#
Represents no states. Can be used with
Context.enable_only()
to disable all states.
- Context.BLEND: int#
Enable/disable blending
- Context.DEPTH_TEST: int#
Enable/disable depth testing
- Context.CULL_FACE: int#
Enable/disable face culling
- Context.RASTERIZER_DISCARD: int#
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: int#
When disabled
Context.point_size
is used.
Primitive Modes#
- Context.POINTS: int#
Each vertex represents a point
- Context.LINES: int#
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: int#
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: int#
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: int#
Vertices 0, 1, and 2 form a triangle. Vertices 3, 4, and 5 form a triangle. And so on.
- Context.TRIANGLE_STRIP: int#
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: int#
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: int#
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: int#
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: int#
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: int#
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: int#
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: int#
Returns the value of the texture element that is nearest (in Manhattan distance) to the specified texture coordinates.
- Context.LINEAR: int#
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: int#
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: int#
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: int#
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: int#
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: int#
(0,0,0,0)
- Context.ONE: int#
(1,1,1,1)
- Context.SRC_COLOR: int#
(Rs0/kR,Gs0/kG,Bs0/kB,As0/kA)
- Context.ONE_MINUS_SRC_COLOR: int#
(1,1,1,1) - (Rs0/kR,Gs0/kG,Bs0/kB,As0/kA)
- Context.SRC_ALPHA: int#
(As0/kA,As0/kA,As0/kA,As0/kA)
- Context.ONE_MINUS_SRC_ALPHA: int#
(1,1,1,1) - (As0/kA,As0/kA,As0/kA,As0/kA)
- Context.DST_ALPHA: int#
(Ad/kA,Ad/kA,Ad/kA,Ad/kA)
- Context.ONE_MINUS_DST_ALPHA: int#
(1,1,1,1) - (Ad/kA,Ad/kA,Ad/kA,Ad/kA)
- Context.DST_COLOR: int#
(Rd/kR,Gd/kG,Bd/kB,Ad/kA)
- Context.ONE_MINUS_DST_COLOR: int#
(1,1,1,1) - (Rd/kR,Gd/kG,Bd/kB,Ad/kA)
Blend Function Shortcuts#
- Context.DEFAULT_BLENDING: tuple#
Shotcut for the default blending
SRC_ALPHA, ONE_MINUS_SRC_ALPHA
- Context.ADDITIVE_BLENDING: tuple#
Shotcut for additive blending
ONE, ONE
- Context.PREMULTIPLIED_ALPHA: tuple#
Shotcut for blend mode when using premultiplied alpha
SRC_ALPHA, ONE
Blend Equations#
Used with Context.blend_equation
.
- Context.FUNC_ADD: int#
source + destination
- Context.FUNC_SUBTRACT: int#
source - destination
- Context.FUNC_REVERSE_SUBTRACT: int#
destination - source
- Context.MIN: int#
Minimum of source and destination
- Context.MAX: int#
Maximum of source and destination
Other Enums#
- Context.FIRST_VERTEX_CONVENTION: int#
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: int#
Specifies the last vertex should be used as the source of data for flat shaded varyings. Used with
Context.provoking_vertex
.
- Context.VERTEX_ATTRIB_ARRAY_BARRIER_BIT: int#
VERTEX_ATTRIB_ARRAY_BARRIER_BIT
- Context.ELEMENT_ARRAY_BARRIER_BIT: int#
ELEMENT_ARRAY_BARRIER_BIT
- Context.UNIFORM_BARRIER_BIT: int#
UNIFORM_BARRIER_BIT
- Context.TEXTURE_FETCH_BARRIER_BIT: int#
TEXTURE_FETCH_BARRIER_BIT
- Context.SHADER_IMAGE_ACCESS_BARRIER_BIT: int#
SHADER_IMAGE_ACCESS_BARRIER_BIT
- Context.COMMAND_BARRIER_BIT: int#
COMMAND_BARRIER_BIT
- Context.PIXEL_BUFFER_BARRIER_BIT: int#
PIXEL_BUFFER_BARRIER_BIT
- Context.TEXTURE_UPDATE_BARRIER_BIT: int#
TEXTURE_UPDATE_BARRIER_BIT
- Context.BUFFER_UPDATE_BARRIER_BIT: int#
BUFFER_UPDATE_BARRIER_BIT
- Context.FRAMEBUFFER_BARRIER_BIT: int#
FRAMEBUFFER_BARRIER_BIT
- Context.TRANSFORM_FEEDBACK_BARRIER_BIT: int#
TRANSFORM_FEEDBACK_BARRIER_BIT
- Context.ATOMIC_COUNTER_BARRIER_BIT: int#
ATOMIC_COUNTER_BARRIER_BIT
- Context.SHADER_STORAGE_BARRIER_BIT: int#
SHADER_STORAGE_BARRIER_BIT
- Context.ALL_BARRIER_BITS: int#
ALL_BARRIER_BITS
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)