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'''OpenGL extension ARB.vertex_buffer_object
This module customises the behaviour of the
OpenGL.raw.GL.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, constants, constant, arrays
from OpenGL import extensions, wrapper
from OpenGL.GL import glget
import ctypes
from OpenGL.raw.GL.ARB.vertex_buffer_object import *
### END AUTOGENERATED SECTION
from OpenGL.lazywrapper import lazy
from OpenGL.arrays import ArrayDatatype
glDeleteBuffersARB = arrays.setInputArraySizeType(
glDeleteBuffersARB,
None,
arrays.GLuintArray,
'buffers',
)
glGenBuffersARB = wrapper.wrapper( glGenBuffersARB ).setOutput(
'buffers', lambda n: (n,), 'n',
)
def _sizeOfArrayInput( pyArgs, index, wrapper ):
return (
arrays.ArrayDatatype.arrayByteCount( pyArgs[index] )
)
@lazy( glBufferDataARB )
def glBufferDataARB( baseOperation, target, size, data=None, usage=None ):
"""Copy given data into the currently bound vertex-buffer-data object
target -- the symbolic constant indicating which buffer type is intended
size -- if provided, the count-in-bytes of the array
data -- data-pointer to be used, may be None to initialize without
copying over a data-set
usage -- hint to the driver as to how to set up access to the buffer
Note: parameter "size" can be omitted, which makes the signature
glBufferData( target, data, usage )
instead of:
glBufferData( target, size, data, usage )
"""
if usage is None:
usage = data
data = size
size = None
data = ArrayDatatype.asArray( data )
if size is None:
size = ArrayDatatype.arrayByteCount( data )
return baseOperation( target, size, data, usage )
@lazy( glBufferSubDataARB )
def glBufferSubDataARB( baseOperation, target, offset, size, data=None ):
"""Copy subset of data into the currently bound vertex-buffer-data object
target -- the symbolic constant indicating which buffer type is intended
offset -- offset from beginning of buffer at which to copy bytes
size -- the count-in-bytes of the array (if an int/long), if None,
calculate size from data, if an array and data is None, use as
data (i.e. the parameter can be omitted and calculated)
data -- data-pointer to be used, may be None to initialize without
copying over a data-set
Note that if size is not an int/long it is considered to be data
"""
try:
if size is not None:
size = int( size )
except TypeError, err:
if data is not None:
raise TypeError(
"""Expect an integer size *or* a data-array, not both"""
)
data = size
size = None
data = ArrayDatatype.asArray( data )
if size is None:
size = ArrayDatatype.arrayByteCount( data )
return baseOperation( target, offset, size, data )
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