opengl.vao.VAO

moderngl_window.opengl.vao.VAO[source]

Represents a vertex array object.

This is a wrapper class over moderngl.VertexArray to make interactions with programs/shaders simpler. Named buffers are added correspoding with attribute names in a vertex shader. When rendering the VAO an internal moderngl.VertextArray is created automatically mapping the named buffers compatible with the supplied program. This program is cached internally.

The shader program doesn’t need to use all the buffers registered in this wrapper. When a subset is used only the used buffers are mapped and the appropriate padding is calculated when interleaved data is used.

You are not required to use this class, but most methods in the system creating vertexbuffers will return this type. You can obtain a single moderngl.VertexBuffer instance by calling VAO.instance() method if you prefer to work directly on moderngl instances.

Example:

# Separate buffers
vao = VAO(name="test", mode=moderngl.POINTS)
vao.buffer(positions, '3f', ['in_position'])
vao.buffer(velocities, '3f', ['in_velocities'])

# Interleaved
vao = VAO(name="test", mode=moderngl.POINTS)
vao.buffer(interleaved_data, '3f 3f', ['in_position', 'in_velocities'])

# GLSL vertex shader in attributes
in vec3 in_position;
in vec3 in_velocities;

Methods

VAO.__init__(name='', mode=4)[source]

Create and empty VAO with a name and default render mode.

Example:

VAO(name="cube", mode=moderngl.TRIANGLES)
Keyword Arguments

  • name (str) – Optional name for debug purposes

  • mode (int) – Default draw mode

VAO.render(program: Program, mode=None, vertices=-1, first=0, instances=1)[source]

Render the VAO.

An internal moderngl.VertexBuffer with compatible buffer bindings is automatically created on the fly and cached internally.

Parameters

program – The moderngl.Program

Keyword Arguments

  • mode – Override the draw mode (TRIANGLES etc)

  • vertices (int) – The number of vertices to transform

  • first (int) – The index of the first vertex to start with

  • instances (int) – The number of instances

VAO.render_indirect(program: Program, buffer, mode=None, count=-1, *, first=0)[source]

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

  • program – The moderngl.Program

  • buffer – The moderngl.Buffer containing indirect draw commands

Keyword Arguments

  • mode (int) – By default TRIANGLES will be used.

  • count (int) – The number of draws.

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

VAO.transform(program: Program, buffer: Buffer, mode=None, vertices=-1, first=0, instances=1)[source]

Transform vertices. Stores the output in a single buffer.

Parameters

  • program – The moderngl.Program

  • buffer – The moderngl.buffer to store the output

Keyword Arguments

  • mode – Draw mode (for example moderngl.POINTS)

  • vertices (int) – The number of vertices to transform

  • first (int) – The index of the first vertex to start with

  • instances (int) – The number of instances

VAO.buffer(buffer, buffer_format: str, attribute_names: List[str])[source]

Register a buffer/vbo for the VAO. This can be called multiple times. adding multiple buffers (interleaved or not).

Parameters

  • buffer – The buffer data. Can be numpy.array, moderngl.Buffer or bytes.

  • buffer_format (str) – The format of the buffer. (eg. 3f 3f for interleaved positions and normals).

  • attribute_names – A list of attribute names this buffer should map to.

Returns

The moderngl.Buffer instance object. This is handy when providing bytes and numpy.array.

VAO.index_buffer(buffer, index_element_size=4)[source]

Set the index buffer for this VAO.

Parameters

buffer – moderngl.Buffer, numpy.array or bytes

Keyword Arguments

index_element_size (int) – Byte size of each element. 1, 2 or 4

VAO.instance(program: Program) → VertexArray[source]

Obtain the moderngl.VertexArray instance for the program.

The instance is only created once and cached internally.

Parameters

program (moderngl.Program) – The program

Returns

instance

Return type

moderngl.VertexArray

VAO.release(buffer=True)[source]

Destroy all internally cached vaos and release all buffers.

Keyword Arguments

buffers (bool) – also release buffers

VAO.get_buffer_by_name(name: str) → BufferInfo[source]

Get the BufferInfo associated with a specific attribute name

If no buffer is associated with the name None will be returned.

Parameters

name (str) – Name of the mapped attribute

Returns

BufferInfo instance

Return type

BufferInfo

Attributes

VAO.ctx

The actite moderngl context

Type

moderngl.Context