ShaderStorageBuffer Class Reference

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

Specialization of Buffer for OpenGL Shader Storage Buffer Object. More...

Inheritance diagram for ShaderStorageBuffer:

Detailed Description

Specialization of Buffer for OpenGL Shader Storage Buffer Object.

SSBOs are the most powerful way to transport data between the CPU and OpenGL shaders and allow for both read and write access.

Example for setting up an SSBO and attaching it to a shader

// define buffer layout of data to be shared with GPU
struct Foo {
    int32_t input = 0;
    float result = 0.f;
};
std::vector<Foo> foos(4, Foo{});
for (int i = 0; i < 4; ++i)
    foos[i].input = i + 1;
 
// create SSBO and upload data
ShaderStorageBuffer ssbo(Buffer::Usage::DynamicDraw);
ssbo.bind();
ssbo.setData(foos);
 
// bind SSBO to shader
Program prog = ...
prog.enable();
prog.bindBuffer("_fooBuffer", ssbo);

Corresponding GLSL shader code:

// define buffer layout on the GPU side, make sure to match the CPU side including potential padding
struct Foo {
    int input;
    float result;
};
layout(std430) buffer _fooBuffer {
    Foo[] foos;
};
 
void main() {
    // access SSBO
    for (int i = 0; i < 4; ++i)
        foos[0].result = computeResult(foos[i].input);
}

Note

SSBOs require at least OpenGL 4.3 or the ARB_shader_storage_buffer_object extension.

See also

https://www.khronos.org/opengl/wiki/Shader_Storage_Buffer_Object

Public Member Functions
	ShaderStorageBuffer (Usage usageHint=Buffer::Usage::StaticDraw)
	Instantiate a new Shader Storage Buffer Object.
void	bindBase (uint32_t index)
	Bind the buffer to the storage block with the given index.
template<typename... Ts>
void	setSubData (size_t offset, std::vector< Ts >... data)
	Upload data into the buffer starting at the given offset.
template<typename T>
void	setData (Utils::Span< T > data)
	Upload data to the buffer.
template<typename T>
void	setData (const std::vector< T > &data)
	Upload data to the buffer.
template<typename T>
void	getData (std::vector< T > &outData)
	Download all data from the buffer attached to the given target that fits into the given vector.
template<typename T>
void	getSubData (int64_t offsetBytes, int64_t sizeBytes, std::vector< T > &outData)
	Download the given range of data of the buffer attached to the given target.
size_t	bufferSize () const
	Returns the number of bytes that were previously allocated on the GPU for this 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.
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 shader storage 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

ShaderStorageBuffer()

ShaderStorageBuffer ( Usage usageHint = Buffer::Usage::StaticDraw )

explicit

Instantiate a new Shader Storage Buffer Object.

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

setSubData() [1/2]

template<typename... Ts>

void setSubData ( size_t offset, std::vector< Ts >... data )

inline

Upload data into the buffer starting at the given offset.

Parameters

offset	Offset in bytes into the buffer object's data store where start writing data.
data	Pack of data arrays that should be copied to the buffer. If you provide multiple spans they will be concatenated and end up next to each other in the buffer without any padding.

setData() [1/2]

template<typename T>

void setData

(

Utils::Span< T >

data

)

Upload data to the buffer.

Note

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

Parameters

data	Contiguous sequence of elements that shall be uploaded to the buffer.

setData() [2/2]

template<typename T>

void setData

(

const std::vector< T > &

data

)

Upload data to the buffer.

Note

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

Parameters

data	Vector of elements that shall be uploaded to the buffer.

getData()

template<typename T>

void getData

(

std::vector< T > &

outData

)

Download all data from the buffer attached to the given target that fits into the given vector.

Note

The buffer needs to be bound before this method is called.

Parameters

outData

Vector in which the data should be downloaded. The size of the vector must correspond the number of bytes to be downloaded.

getSubData()

template<typename T>

void getSubData	(	int64_t	offsetBytes,
		int64_t	sizeBytes,
		std::vector< T > &	outData )

Download the given range of data of the buffer attached to the given target.

Note

The buffer needs to be bound before this method is called.

Parameters

offsetBytes	Specifies the offset into the buffer object's data store from which data will be returned, measured in bytes.
sizeBytes	Specifies the size in bytes of the data store region being returned.
outData	Vector into which the data should be downloaded, will be resized to fit the data.

allocateBuffer()

void allocateBuffer

(

int64_t

numBytes

)

Allocates storage on the GPU for this buffer object.

Parameters

numBytes

Number of bytes to allocate.

setSubData() [2/2]

template<typename... Ts>

void setSubData	(	size_t	offset,
		Utils::Span< Ts >...	data )

Upload data into the buffer starting at the given offset.

Parameters

offset	Offset in bytes into the buffer object's data store where start writing data.
data	Pack of data arrays that should be copied to the buffer. If you provide multiple spans they will be concatenated and end up next to each other in the buffer without any padding.

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

• ImFusion/Core/GL/ShaderStorageBuffer.h