VertexArrayObject Class Reference

#include <ImFusion/Core/GL/VertexBuffer.h>

Wrapper around an OpenGL Vertex Array Object (VAO) to define the vertex attribute specification for rendering. More...

Inheritance diagram for VertexArrayObject:

Detailed Description

Wrapper around an OpenGL Vertex Array Object (VAO) to define the vertex attribute specification for rendering.

In the vast majority of use cases you do not need to use this class explicitly because VertexBuffer will take care of it internally. However, it may be useful in one of the following situations:

• Hot render loops where the same VBO is rendered multiple times with the exact same attribute configuration can be accelerated by setting up a VertexArrayObject instance once and using this to issue draw commands.
• You store rendering data in multiple VBOs and need to pass them to the same shader in a combined fashion.

After instantiating a VertexArrayObject you must call setAttributes() once in order to configure the VBO and optionally IBO mapping to the shader input. Afterwards, you can call its draw() functions as many times as you like. Keep in mind that the currently bound VAO is part of the global OpenGL state and other library calls may change it at any time.

// setup VBOs first
VertexBuffer vertices = ...;
vertices.bind();
vertices.setData(...);
VertexBuffer otherVertexData = ...;
otherVertexData.bind();
otherVertexData.setData(...);
 
// Instantiate the VAO and configure its vertex attributes to pull data from the given VBOs.
// From now on vbo will use this fixed vertex array object during subsequent draw calls.
// The first two attributes in VBO `vertices` will be passed to input locations 0 and 3 of
// the vertex shader, the first two attributes in `otherVertexData` to locations 1 and 2.
VertexArrayObject vao;
vao.setAttributes({{&vertices, {0, 3}}, {&otherVertexData, {1, 2}}});
 
for (...) {
    // Perform the rendering, make sure to *not* change the VBO attribute configuration.
    // If you draw other VBOs/VAOs in between you will need to rebind `vao`.
    vao.draw(...);
}

Note

This interface is still experimental and its API may change in the future.

See also

• https://www.khronos.org/opengl/wiki/Vertex_Specification#Vertex_Array_Object
• VertexBuffer
• IndexBuffer

Public Member Functions
void	setAttributes (const VertexBuffer &vbo, const IndexBuffer *ibo=nullptr)
	Configure the VAO with the current attribute configuration of the vertex buffer and an optional index buffer.
void	setAttributes (std::initializer_list< std::pair< const VertexBuffer *, std::initializer_list< int > > > vboMapping, const IndexBuffer *ibo=nullptr)
	Configure the VAO with the current attribute configuration of multiple vertex buffers and an optional index buffer.
void	bind () const
	Rebind the VAO, useful if you issued any other rendering command in between.
void	draw (Primitive mode) const
	Renders a single primitive using all vertices of the previously bound VBOs/IBO.
void	drawInstanced (Primitive mode, int32_t count) const
	Renders multiple instances of the same primitive using all vertices of the previously bound VBOs/IBO.

Static Public Member Functions
static void	unbind ()
	Unbind any previously bound VAO.

Member Function Documentation

setAttributes() [1/2]

void setAttributes	(	const VertexBuffer &	vbo,
		const IndexBuffer *	ibo = nullptr )

Configure the VAO with the current attribute configuration of the vertex buffer and an optional index buffer.

Use the other overload to configure the VAO to use vertex data from multiple VBOs.

Warning

Both vbo and ibo must be fully configured at this point. You may exchange the underlying data but must not change any attribute configuration afterwards when using the VAO.

setAttributes() [2/2]

void setAttributes	(	std::initializer_list< std::pair< const VertexBuffer *, std::initializer_list< int > > >	vboMapping,
		const IndexBuffer *	ibo = nullptr )

Configure the VAO with the current attribute configuration of multiple vertex buffers and an optional index buffer.

vboMapping receives a list of vertex buffers paired with a list of the vertex buffer input locations for each attribute in the VBO. All provided VBOs must hold the same number of elements per attribute. The VertexBuffer pointers must not be null.

Warning

All VBOs and the optional IBO must be fully configured at this point. You may exchange the underlying data but must not change any attribute configuration afterwards when using the VAO.

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The documentation for this class was generated from the following file:

• ImFusion/Core/GL/VertexBuffer.h