blob: f6522449b63394cdf625b9d82a8c6ae3a31a8e3d [file] [log] [blame]
Name Strings
Rick Hammerstone, AMD (rick.hammerstone 'at'
0.3 - 11/04/06
Updated contact info after ATI/AMD merger.
0.2 - 01/15/01
Modified map call to return a pointer and take a single <buffer>
argument. Cleaned up spec.
0.1 - 11/26/01
Initial revision
This extension is written against the OpenGL 1.2.1 Specification.
OpenGL 1.1 is required. ATI_vertex_array_object is required by
this extension.
This extension provides a mechanism for an application to obtain
the virtual address of an object buffer. This allows the
application to directly update the contents of an object buffer
and avoid any intermediate copies.
Should we use Lock and Unlock terminology?
UNRESOLVED: This could be confusing. D3D uses "Lock" to mean
that something is available for the application to update and
won't be changed by the driver. However, in the compiled
vertex array extension, "Lock" is used to mean that the
application will not be changing the contents of a vertex
New Procedures and Functions
void *MapObjectBufferATI(uint buffer)
void UnmapObjectBufferATI(uint buffer)
New Tokens
Additions to Chapter 2 of the GL Specification (OpenGL Operation)
Added to the description of Vertex Array Objects:
The object buffer interface provides a mechanism for an
application to store data in persistent memory that can be
accessed directly by the graphics hardware. The memory is accessed
through handles, and data must be copied into the memory by the
driver. This provides a platform-independent mechanism for
updating the object buffers, and allows the driver to optimally
manage the object buffers.
However, in cases where object buffers are being frequently
updated, the overhead of memory copies can degrade overall
application performance. The command
void *MapObjectBufferATI(uint buffer)
allows the application to obtain a pointer to the object buffer
named <buffer>. If <buffer> is not the name of an existing object
buffer, MapObjectBufferATI returns a null pointer.
The size of the region mapped by MapObjectBufferATI is equal to
the size of the object buffer. This size can be queried by calling
GetObjectBufferivATI or GetObjectBufferfvATI with the token
When an application issues a MapObjectBufferATI command, all
rendering commands that reference data stored in <buffer> must
complete before the call to MapObjectBufferATI returns. When the
call returns, the data in <buffer> can be updated immediately.
If an application desires to update an object buffer using this
interface, it should create the object buffer using DYNAMIC_ATI as
the usage parameter. Direct updates to object buffers that were
created with STATIC_ATI as the usage parameter may operate at
reduced performance.
When an application is finished updating an object buffer, it uses
the command
void UnmapObjectBufferATI(uint buffer)
to indicate to the driver that it has completed updating the
object buffer specified by <buffer>. An application must call
UnmapObjectBufferATI before issuing any rendering commands that
use the data stored in <buffer>.
Attempts to update an object buffer by direct memory writes after
UnmapObjectBufferATI has been called result in undefined behavior
and may generate an error. UpdateObjectBufferATI can be used to
update an object buffer at any time, regardless of whether it is
mapped or not.
Additions to Chapter 3 of the 1.2.1 Specification (Rasterization)
Additions to Chapter 4 of the 1.2.1 Specification (Per-Fragment
Operations and the Frame Buffer)
Additions to Chapter 5 of the 1.2.1 Specification (Special Functions)
Added to section 5.4, as part of the discussion of what commands
are compiled into display lists:
MapObjectBufferATI and UnmapObjectBufferATI are not included in
display lists, but are executed immediately.
Additions to Chapter 6 of the 1.2.1 Specification (State and State
INVALID_VALUE is generated if the <buffer> argument of
MapObjectBuffer or UnmapObjectBuffer does not specify a valid
object buffer.
INVALID_OPERATION may be generated if a rendering command is
issued that uses an object buffer that is currently mapped.
New State
Implementation Notes