Context¶

class moderngl.Context¶: Class exposing OpenGL features. ModernGL objects can be created from this class.

Create¶

moderngl.create_context(require=None) → 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 **settings – Other backend specific settings
Returns:	`Context` object

moderngl.create_standalone_context(require=None) → 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.
Returns:	`Context` object

ModernGL Objects¶

Context.program(vertex_shader, fragment_shader=None, geometry_shader=None, tess_control_shader=None, tess_evaluation_shader=None, varyings=()) → Program¶

Create a Program object.

Only linked programs will be returned.

A single shader in the shaders parameter is also accepted. The varyings are only used when a transform program is created.

Parameters:	shaders (list) – A list of `Shader` objects. varyings (list) – A list of varying names.
Returns:	`Program` object

Context.simple_vertex_array(program, buffer, *attributes, index_buffer=None, index_element_size=4) → 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.

Keyword Arguments:
Parameters:	program (Program) – The program used when rendering. buffer (Buffer) – The buffer. attributes (list) – A list of attribute names.
	index_element_size (int) – byte size of each index element, 1, 2 or 4. index_buffer (Buffer) – An index buffer.
Returns:	`VertexArray` object

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

Create a VertexArray object.

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

Keyword Arguments:
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.
	index_element_size (int) – byte size of each index element, 1, 2 or 4. skip_errors (bool) – Ignore skip_errors varyings.
Returns:	`VertexArray` object

Context.buffer(data=None, reserve=0, dynamic=False) → Buffer¶

Create a Buffer object.

Keyword Arguments:
Parameters:	data (bytes) – Content of the new buffer.
	reserve (int) – The number of bytes to reserve. dynamic (bool) – Treat buffer as dynamic.
Returns:	`Buffer` object

Context.texture(size, components, data=None, samples=0, alignment=1, dtype='f1', internal_format=None) → 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.

Keyword Arguments:
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)
Returns:	`Texture` object

Context.depth_texture(size, data=None, samples=0, alignment=4) → Texture¶

Create a Texture object.

Keyword Arguments:
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.
Returns:	`Texture` object

Context.texture3d(size, components, data=None, alignment=1, dtype='f1') → Texture3D¶

Create a Texture3D object.

Keyword Arguments:
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.
Returns:	`Texture3D` object

Context.texture_array(size, components, data=None, alignment=1, dtype='f1') → TextureArray¶

Create a TextureArray object.

Keyword Arguments:
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.
Returns:	`Texture3D` object

Context.texture_cube(size, components, data=None, alignment=1, dtype='f1') → TextureCube¶

Create a TextureCube object.

Keyword Arguments:
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.
Returns:	`TextureCube` object

Context.simple_framebuffer(size, components=4, samples=0, dtype='f1') → Framebuffer¶

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

Keyword Arguments:
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.
Returns:	`Framebuffer` object

Context.framebuffer(color_attachments=(), depth_attachment=None) → 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, components=4, samples=0, dtype='f1') → Renderbuffer¶

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

Keyword Arguments:
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.
Returns:	`Renderbuffer` object

Context.depth_renderbuffer(size, samples=0) → Renderbuffer¶

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

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

Context.scope(framebuffer=None, enable_only=None, textures=(), uniform_buffers=(), storage_buffers=(), samplers=(), enable=None) → Scope¶

Create a Scope object.

Keyword Arguments:
Parameters:	framebuffer (Framebuffer) – The framebuffer to use when entering. enable_only (int) – The enable_only flags to set when entering.
	textures (list) – List of (texture, binding) tuples. uniform_buffers (list) – List of (buffer, binding) tuples. storage_buffers (list) – List of (buffer, binding) tuples. samplers (list) – List of sampler bindings enable (int) – Flags to enable for this vao such as depth testing and blending

Context.query(samples=False, any_samples=False, time=False, primitives=False) → 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) → 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=True, repeat_y=True, repeat_z=True, filter=None, anisotropy=1.0, compare_func='?', border_color=None, min_lod=-1000.0, max_lod=1000.0, texture=None) → 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=0, end=-1)¶

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()¶

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=0.0, green=0.0, blue=0.0, alpha=0.0, depth=1.0, viewport=None, color=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.

Keyword Arguments:
Parameters:	red (float) – color component. green (float) – color component. blue (float) – color component. alpha (float) – alpha component. depth (float) – depth value.
	viewport (tuple) – The viewport.

Context.enable_only(flags)¶

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)

Parameters:	flags (EnableFlag) – The flags to enable

Context.enable(flags)¶

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)¶

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.finish()¶: Wait for all drawing commands to finish.

Context.copy_buffer(dst, src, size=-1, read_offset=0, write_offset=0)¶

Copy buffer content.

Keyword Arguments:
Parameters:	dst (Buffer) – The destination buffer. src (Buffer) – The source buffer. size (int) – The number of bytes to copy.
	read_offset (int) – The read offset. write_offset (int) – The write offset.

Context.copy_framebuffer(dst, src)¶

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=None) → Framebuffer¶

Detect 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.__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.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.

float: Set the default line width.

Context.point_size¶

Set/get the default point size.

Type:	float

Context.depth_func¶

Set the default depth func. The depth function is set using a string.

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:	int

Context.blend_func¶

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

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¶

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_func = moderngl.FUNC_ADD

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

Type:	tuple

Context.viewport¶

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¶

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¶

The OpenGL version code. Reports 410 for OpenGL 4.1

Type:	int

Context.screen¶

A Framebuffer instance representing the screen usually 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.

Type:	Framebuffer

Context.fbo¶

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

Type:	Framebuffer

Context.front_face¶

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¶

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¶

Wireframe settings for debugging.

Type:	bool

Context.max_samples¶

The maximum supported number of samples for multisampling

Type:	int

Context.max_integer_samples¶

The max integer samples.

Type:	int

Context.max_texture_units¶

The max texture units.

Type:	int

Context.default_texture_unit¶

The default texture unit.

Type:	int

Context.max_anisotropy¶

The maximum value supported for anisotropic filtering.

Type:	float

Context.multisample¶

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¶

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

Type:	int

Context.provoking_vertex¶

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.error¶

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¶

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¶

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¶: Internal representation for debug purposes only.

Context.extra¶: 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 = 0¶: Represents no states. Can be used with Context.enable_only() to disable all states.

Context.BLEND = 1¶: Enable/disable blending

Context.DEPTH_TEST = 2¶: Enable/disable depth testing

Context.CULL_FACE = 4¶: Enable/disable face culling

Context.RASTERIZER_DISCARD = 8¶: Enable/disable rasterization

Context.PROGRAM_POINT_SIZE = 16¶: When enabled we can write to gl_PointSize in the vertex shader to specify the point size. When disabled Context.point_size is used.

Primitive Modes¶

Context.POINTS = 0¶: Each vertex represents a point

Context.LINES = 1¶: 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 = 2¶: 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 = 3¶: 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 = 4¶: Vertices 0, 1, and 2 form a triangle. Vertices 3, 4, and 5 form a triangle. And so on.

Context.TRIANGLE_STRIP = 5¶: 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 = 6¶: 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 = 10¶: 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 = 11¶: 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 = 12¶: 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 = 13¶: 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 = 14¶: 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 = 9728¶: Returns the value of the texture element that is nearest (in Manhattan distance) to the specified texture coordinates.

Context.LINEAR = 9729¶: 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 = 9984¶: 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 = 9985¶: 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 = 9986¶: 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 = 9987¶: 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 = 0¶: (0,0,0,0)

Context.ONE = 1¶: (1,1,1,1)

Context.SRC_COLOR = 768¶: (Rs0/kR,Gs0/kG,Bs0/kB,As0/kA)

Context.ONE_MINUS_SRC_COLOR = 769¶: (1,1,1,1) − (Rs0/kR,Gs0/kG,Bs0/kB,As0/kA)

Context.SRC_ALPHA = 770¶: (As0/kA,As0/kA,As0/kA,As0/kA)

Context.ONE_MINUS_SRC_ALPHA = 771¶: (1,1,1,1) − (As0/kA,As0/kA,As0/kA,As0/kA)

Context.DST_ALPHA = 772¶: (Ad/kA,Ad/kA,Ad/kA,Ad/kA)

Context.ONE_MINUS_DST_ALPHA = 773¶: (1,1,1,1) − (Ad/kA,Ad/kA,Ad/kA,Ad/kA)

Context.DST_COLOR = 774¶: (Rd/kR,Gd/kG,Bd/kB,Ad/kA)

Context.ONE_MINUS_DST_COLOR = 775¶: (1,1,1,1) − (Rd/kR,Gd/kG,Bd/kB,Ad/kA)

Blend Function Shortcuts¶

Context.DEFAULT_BLENDING = (770, 771)¶: Shotcut for the default blending SRC_ALPHA, ONE_MINUS_SRC_ALPHA

Context.ADDITIVE_BLENDING = (1, 1)¶: Shotcut for additive blending ONE, ONE

Context.PREMULTIPLIED_ALPHA = (770, 1)¶: Shotcut for blend mode when using premultiplied alpha SRC_ALPHA, ONE

Blend Equations¶

Used with Context.blend_equation.

Context.FUNC_ADD = 32774¶: source + destination

Context.FUNC_SUBTRACT = 32778¶: source - destination

Context.FUNC_REVERSE_SUBTRACT = 32779¶: destination - source

Context.MIN = 32775¶: Minimum of source and destination

Context.MAX = 32776¶: Maximum of source and destination

Other Enums¶

Context.FIRST_VERTEX_CONVENTION = 36429¶: 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 = 36430¶: Specifies the last vertex should be used as the source of data for flat shaded varyings. Used with Context.provoking_vertex.

Examples¶

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

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

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)