| | '''OpenGL extension EXT.pixel_buffer_object |
| | |
| | This module customises the behaviour of the |
| | OpenGL.raw.GL.EXT.pixel_buffer_object to provide a more |
| | Python-friendly API |
| | |
| | Overview (from the spec) |
| | |
| | This extension expands on the interface provided by buffer objects. |
| | It is intended to permit buffer objects to be used not only with |
| | vertex array data, but also with pixel data. |
| | Buffer objects were promoted from the ARB_vertex_buffer_object |
| | extension in OpenGL 1.5. |
| | |
| | Recall that buffer objects conceptually are nothing more than arrays |
| | of bytes, just like any chunk of memory. Buffer objects allow GL |
| | commands to source data from a buffer object by binding the buffer |
| | object to a given target and then overloading a certain set of GL |
| | commands' pointer arguments to refer to offsets inside the buffer, |
| | rather than pointers to user memory. An offset is encoded in a |
| | pointer by adding the offset to a null pointer. |
| | |
| | This extension does not add any new functionality to buffer |
| | objects themselves. It simply adds two new targets to which buffer |
| | objects can be bound: PIXEL_PACK_BUFFER and PIXEL_UNPACK_BUFFER. |
| | When a buffer object is bound to the PIXEL_PACK_BUFFER target, |
| | commands such as ReadPixels write their data into a buffer object. |
| | When a buffer object is bound to the PIXEL_UNPACK_BUFFER target, |
| | commands such as DrawPixels read their data from a buffer object. |
| | |
| | There are a wide variety of applications for such functionality. |
| | Some of the most interesting ones are: |
| | |
| | - "Render to vertex array." The application can use a fragment |
| | program to render some image into one of its buffers, then read |
| | this image out into a buffer object via ReadPixels. Then, it can |
| | use this buffer object as a source of vertex data. |
| | |
| | - Streaming textures. If the application uses MapBuffer/UnmapBuffer |
| | to write its data for TexSubImage into a buffer object, at least |
| | one of the data copies usually required to download a texture can |
| | be eliminated, significantly increasing texture download |
| | performance. |
| | |
| | - Asynchronous ReadPixels. If an application needs to read back a |
| | number of images and process them with the CPU, the existing GL |
| | interface makes it nearly impossible to pipeline this operation. |
| | The driver will typically send the hardware a readback command |
| | when ReadPixels is called, and then wait for all of the data to |
| | be available before returning control to the application. Then, |
| | the application can either process the data immediately or call |
| | ReadPixels again; in neither case will the readback overlap with |
| | the processing. If the application issues several readbacks into |
| | several buffer objects, however, and then maps each one to process |
| | its data, then the readbacks can proceed in parallel with the data |
| | processing. |
| | |
| | The official definition of this extension is available here: |
| | http://www.opengl.org/registry/specs/EXT/pixel_buffer_object.txt |
| | ''' |
| | from OpenGL import platform, constant, arrays |
| | from OpenGL import extensions, wrapper |
| | import ctypes |
| | from OpenGL.raw.GL import _types, _glgets |
| | from OpenGL.raw.GL.EXT.pixel_buffer_object import * |
| | from OpenGL.raw.GL.EXT.pixel_buffer_object import _EXTENSION_NAME |
| |
|
| | def glInitPixelBufferObjectEXT(): |
| | '''Return boolean indicating whether this extension is available''' |
| | from OpenGL import extensions |
| | return extensions.hasGLExtension( _EXTENSION_NAME ) |
| |
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| |
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| | |
