| '''OpenGL extension ARB.vertex_buffer_object |
| |
| This module customises the behaviour of the |
| OpenGL.raw.GLX.ARB.vertex_buffer_object to provide a more |
| Python-friendly API |
| |
| Overview (from the spec) |
| |
| This extension defines an interface that allows various types of data |
| (especially vertex array data) to be cached in high-performance |
| graphics memory on the server, thereby increasing the rate of data |
| transfers. |
| |
| Chunks of data are encapsulated within "buffer objects", which |
| conceptually are nothing more than arrays of bytes, just like any |
| chunk of memory. An API is provided whereby applications can read |
| from or write to buffers, either via the GL itself (glBufferData, |
| glBufferSubData, glGetBufferSubData) or via a pointer to the memory. |
| |
| The latter technique is known as "mapping" a buffer. When an |
| application maps a buffer, it is given a pointer to the memory. When |
| the application finishes reading from or writing to the memory, it is |
| required to "unmap" the buffer before it is once again permitted to |
| use that buffer as a GL data source or sink. Mapping often allows |
| applications to eliminate an extra data copy otherwise required to |
| access the buffer, thereby enhancing performance. In addition, |
| requiring that applications unmap the buffer to use it as a data |
| source or sink ensures that certain classes of latent synchronization |
| bugs cannot occur. |
| |
| Although this extension only defines hooks for buffer objects to be |
| used with OpenGL's vertex array APIs, the API defined in this |
| extension permits buffer objects to be used as either data sources or |
| sinks for any GL command that takes a pointer as an argument. |
| Normally, in the absence of this extension, a pointer passed into the |
| GL is simply a pointer to the user's data. This extension defines |
| a mechanism whereby this pointer is used not as a pointer to the data |
| itself, but as an offset into a currently bound buffer object. The |
| buffer object ID zero is reserved, and when buffer object zero is |
| bound to a given target, the commands affected by that buffer binding |
| behave normally. When a nonzero buffer ID is bound, then the pointer |
| represents an offset. |
| |
| In the case of vertex arrays, this extension defines not merely one |
| binding for all attributes, but a separate binding for each |
| individual attribute. As a result, applications can source their |
| attributes from multiple buffers. An application might, for example, |
| have a model with constant texture coordinates and variable geometry. |
| The texture coordinates might be retrieved from a buffer object with |
| the usage mode "STATIC_DRAW", indicating to the GL that the |
| application does not expect to update the contents of the buffer |
| frequently or even at all, while the vertices might be retrieved from |
| a buffer object with the usage mode "STREAM_DRAW", indicating that |
| the vertices will be updated on a regular basis. |
| |
| In addition, a binding is defined by which applications can source |
| index data (as used by DrawElements, DrawRangeElements, and |
| MultiDrawElements) from a buffer object. On some platforms, this |
| enables very large models to be rendered with no more than a few |
| small commands to the graphics device. |
| |
| It is expected that a future extension will allow sourcing pixel data |
| from and writing pixel data to a buffer object. |
| |
| The official definition of this extension is available here: |
| http://www.opengl.org/registry/specs/ARB/vertex_buffer_object.txt |
| ''' |
| from OpenGL import platform, constant, arrays |
| from OpenGL import extensions, wrapper |
| import ctypes |
| from OpenGL.raw.GLX import _types, _glgets |
| from OpenGL.raw.GLX.ARB.vertex_buffer_object import * |
| from OpenGL.raw.GLX.ARB.vertex_buffer_object import _EXTENSION_NAME |
|
|
| def glInitVertexBufferObjectARB(): |
| '''Return boolean indicating whether this extension is available''' |
| from OpenGL import extensions |
| return extensions.hasGLExtension( _EXTENSION_NAME ) |
|
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| |
