Class buffer

Class Documentation

class legion::rendering::buffer

Low level rendering buffer that can be used for all kinds of purposes. Depending on the target it could be a vertex buffer or shader storage buffer or something else.

Public Functions

buffer() = default

Faux constructor. To prevent unnecessary GPU allocations the default constructor doesn’t actually create a buffer. This means that default initialized buffers are invalid temporary objects until they get properly initialized.

template<typename T>
buffer(GLenum target, const std::vector<T> &data, GLenum usage)

Main allocating constructor. This constructor actually creates the GPU side buffer and binds it to this instance.

Note

Read more at docs.gl.

Parameters

  • target: The buffer type to create. eg: GL_ARRAY_BUFFER, GL_SHADER_STORAGE_BUFFER

  • data: Vector of data to store in the buffers VRAM allocation.

  • usage: Intended memory usage. eg: GL_STATIC_DRAW (Data doesn’t change and ised for drawing many times), GL_DYNAMIC_READ (Changes all the time and is used for reading back to CPU)

buffer(GLenum target, size_type size, void *data, GLenum usage)

Main allocating constructor. This constructor actually creates the GPU side buffer and binds it to this instance.

Note

Read more at docs.gl.

Note

If the buffer is allocated with a nullptr as the data pointer then the memory in VRAM may be garbage when read. Do not assume null writes to happen.

Parameters

  • target: The buffer type to create. eg: GL_ARRAY_BUFFER, GL_SHADER_STORAGE_BUFFER

  • size: Size in bytes to allocate on VRAM.

  • data: Data to send to VRAM. This may be a nullptr if you only want to allocate VRAM but keep the memory empty.

  • usage: Intended memory usage. eg: GL_STATIC_DRAW (Data doesn’t change and ised for drawing many times), GL_DYNAMIC_READ (Changes all the time and is used for reading back to CPU)

buffer(GLenum target, GLenum usage)

Main non allocating constructor. This constructor actually creates the GPU side buffer and binds it to this instance.

Note

This constructor doesn’t actually allocate any VRAM to this buffer yet and requires a bufferData call in order to allocate memory for it.

Parameters

  • target: The buffer type to create. eg: GL_ARRAY_BUFFER, GL_SHADER_STORAGE_BUFFER

  • usage: Intended memory usage. eg: GL_STATIC_DRAW (Data doesn’t change and ised for drawing many times), GL_DYNAMIC_READ (Changes all the time and is used for reading back to CPU)

app::gl_id id() const

Returns the rendering API id of the buffer. Useful for low level native rendering.

GLenum target() const

Returns the rendering API type/target of the buffer. Useful for low level native rendering.

GLenum usage() const

Returns the rendering API intended memory usage of the buffer. Useful for low level native rendering.

size_type size() const

Returns the current size of the buffer in bytes.

void bindBufferBase(uint index) const

Bind buffer to a set indexed buffer binding location in shaders.

Note

Read more at docs.gl.

Note

Target must be GL_ATOMIC_COUNTER_BUFFER, GL_TRANSFORM_FEEDBACK_BUFFER, GL_UNIFORM_BUFFER or GL_SHADER_STORAGE_BUFFER.

Parameters

  • index: Indexed buffer binding location to bind to.

void resize(size_type newSize) const

Resize the buffer to a new size. This reallocates VRAM and thus invalidates all data in the buffer.

template<typename T>
inline void bufferData(const std::vector<T> &data) const

Send new data to the VRAM of the buffer. This may reallocate the buffer if the size of the new data is larger than the previously allocated VRAM.

Parameters

  • data: Vector with the data to send.

void bufferData(size_type size, void *data) const

Send new data to the VRAM of the buffer. This may reallocate the buffer if the size of the new data is larger than the previously allocated VRAM.

Parameters

  • size: Size the data to send.

  • data: Pointer to the data to send. (Should not be a nullptr, if you only want to allocate/reallocate then use the resize function.)

void bufferData(size_type offset, size_type size, void *data) const

Send new data to the VRAM of the buffer with a certain offset. This function does not reallocate data and thus the sum of offset + size cannot be more that the size of the buffer.

Parameters

  • offset: Offset since the start of the buffer in bytes.

  • size: Size of the new data in bytes.

  • data: Pointer to the new data to write.

void bind() const

Bind the buffer to the current context. Useful for low level native rendering.

void release() const

Release the buffer from the current context. Useful for low level native rendering.