IndexBuffer Class Reference

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

Specialization of Buffer to store vertex index data (GL_ELEMENT_ARRAY_BUFFER). More...

Inheritance diagram for IndexBuffer:

Detailed Description

Specialization of Buffer to store vertex index data (GL_ELEMENT_ARRAY_BUFFER).

Can be passed to a GL::VertexBuffer::draw() call for indexed rendering where the same vertex data can be used by multiple vertices to reduce memory usage.

Example for rendering a quad using indexed rendering:

// vertex data describing 4 vertices
std::vector<vec2f> vertices = {
    vec2f(-1.0, -1.0),
    vec2f( 1.0, -1.0),
    vec2f(-1.0,  1.0),
    vec2f( 1.0,  1.0)
};
VertexBuffer vbo;
vbo.bind();
vbo.setData(vertices);
 
// index data to render two triangles of 3 vertices each
std::vector<uint16_t> indices = {
    0, 1, 2, 1, 2, 3
};
IndexBuffer ibo;
ibo.bind();
ibo.setData(indices);
 
// Note that this is an artificial example to showcase the usage of index buffers.
// You could achieve the same rendering result with the vertex data only and using
// the Primitive::TriangleStrip primitive instead.
vbo.draw(Primitive::Triangles, ibo);

Warning

In WebGL, the PRIMITIVE_RESTART_FIXED_INDEX option is always enabled. If an index is the maximum for the data type (i.e. 0xFF, 0xFFFF or 0xFFFFFFFF), it is not treated as a regular index, but will restart the primitive. To maintain compatibility, make sure to only use indices smaller than the maximum and only use the maximum in setPrimitiveRestartIndex. See the WebGL Spec for details.

See also

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

Public Member Functions
	IndexBuffer (Usage usageHint=Buffer::Usage::StaticDraw)
	Default constructs an empty index buffer.
uint32_t	primitiveRestartIndex () const
	Returns the OpenGL primitive restart index to use during indexed rendering.
void	setPrimitiveRestartIndex (uint32_t value)
	Sets the OpenGL primitive restart index to use during indexed rendering.
size_t	numElements () const
	Return the number of indices stored in the buffer.
PixelType	type () const
	Return the index data type.
void	setData (Utils::Span< uint8_t > indices)
	Upload uint8_t vertex indices to the buffer.
void	setData (Utils::Span< uint16_t > indices)
	Upload uint16_t vertex indices to the buffer.
void	setData (Utils::Span< uint32_t > indices)
	Upload uint32_t vertex indices to the buffer.
void	setData (Utils::Span< vec3i > indices)
	Upload non-negative int32_t triplets describing a series of triangles to the vertex index buffer.
Public Member Functions inherited from Buffer
	Buffer (Target target, Usage usage)
	Creates a new Buffer.
void	bind () const
	Binds the buffer to the target given during construction.
Usage	usageHint () const
	Returns the buffer usage hint passed to OpenGL during allocation.
void	setUsageHint (Usage value)
	Sets the buffer usage hint passed to OpenGL during allocation.
uint32_t	id () const
	Return a handle to the internal OpenGL buffer object.

Static Public Member Functions
static void	unbind ()
	Unbind any bound index buffer.
Static Public Member Functions inherited from Buffer
static void	unbind (Target target)
	Binds 0 to the specified target.

Additional Inherited Members
Public Types inherited from Buffer
enum class	Target {   Array = 0x8892 , AtomicCounter = 0x92C0 , CopyRead = 0x8F36 , CopyWrite = 0x8F37 ,   DrawIndirect = 0x8F3F , ElementArray = 0x8893 , PixelPack = 0x88EB , PixelUnpack = 0x88EC ,   ShaderStorage = 0x90D2 , Texture = 0x8C2A , TransformFeedback = 0x8C8E , Uniform = 0x8A11 }
	Enumeration of the different OpenGL buffer types. More...
enum class	Usage {   StreamDraw = 0x88E0 , StreamRead = 0x88E1 , StreamCopy = 0x88E2 , StaticDraw = 0x88E4 ,   StaticRead = 0x88E5 , StaticCopy = 0x88E6 , DynamicDraw = 0x88E8 , DynamicRead = 0x88E9 ,   DynamicCopy = 0x88EA }
	Enumeration for usage pattern hints to provide to the GPU when allocating data. More...
Protected Member Functions inherited from Buffer
void	allocateBuffer (int64_t numBytes)
	Allocates storage on the GPU for this buffer object.
template<typename... Ts>
void	setSubData (size_t offset, Utils::Span< Ts >... data)
	Upload data into the buffer starting at the given offset.
template<typename... Ts>
size_t	getBufferSize (Utils::Span< Ts >... data) const
	Compute the total number of bytes used by all provided data together.
Static Protected Member Functions inherited from Buffer
static void	glBufferSubDataImpl (Target target, int64_t offset, int64_t size, const void *data)
	forwards to OpenGL's glBufferSubData().
static void	glGetBufferSubDataImpl (Target target, int64_t offset, int64_t size, void *data)
	forwards to OpenGL's glGetBufferSubData().
Protected Attributes inherited from Buffer
const Target	m_target
	Target binding point for the buffer, will never change for a Buffer instance.
Usage	m_usageHint
	Buffer usage hint passed to OpenGL unless explicitly specified otherwise.
uint32_t	m_id = 0
	Internal OpenGL handle to buffer object.
int64_t	m_bufferSize = 0
	Number of bytes allocated on the GPU.

Constructor & Destructor Documentation

IndexBuffer()

IndexBuffer

(

Usage

usageHint = Buffer::Usage::StaticDraw

)

Default constructs an empty index buffer.

Parameters

usageHint

Expected usage pattern of the buffer

Exceptions

std::runtime_error

if the corresponding OpenGL buffer object could not be created.

Member Function Documentation

primitiveRestartIndex()

uint32_t primitiveRestartIndex

(

)

const

Returns the OpenGL primitive restart index to use during indexed rendering.

The primitive restart feature is disabled if the index is 0 (default behavior).

setPrimitiveRestartIndex()

void setPrimitiveRestartIndex

(

uint32_t

value

)

Sets the OpenGL primitive restart index to use during indexed rendering.

The primitive restart feature is disabled if the index is 0 (default behavior). On WebGL, the features is always enabled. Check the class documentation for details.

setData() [1/4]

void setData

(

Utils::Span< uint8_t >

indices

)

Upload uint8_t vertex indices to the buffer.

The buffer needs to be bound before this method is called. Any previous data will be deleted.

Parameters

indices

Contiguous sequence of index data that should be copied to the buffer.

setData() [2/4]

void setData

(

Utils::Span< uint16_t >

indices

)

Upload uint16_t vertex indices to the buffer.

The buffer needs to be bound before this method is called. Any previous data will be deleted.

Parameters

indices

Contiguous sequence of index data that should be copied to the buffer.

setData() [3/4]

void setData

(

Utils::Span< uint32_t >

indices

)

Upload uint32_t vertex indices to the buffer.

The buffer needs to be bound before this method is called. Any previous data will be deleted.

Parameters

indices

Contiguous sequence of index data that should be copied to the buffer.

setData() [4/4]

void setData

(

Utils::Span< vec3i >

indices

)

Upload non-negative int32_t triplets describing a series of triangles to the vertex index buffer.

The buffer needs to be bound before this method is called. Any previous data will be deleted.

Parameters

indices

Contiguous sequence of index data that should be copied to the buffer. Must not contain any negative elements.

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

• ImFusion/Core/GL/IndexBuffer.h