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Name Strings
$Date: 1996/11/21 00:52:19 $ $Revision: 1.3 $
This extension defines an interface which allows static vertex array
data to be cached or pre-compiled for more efficient rendering. This
is useful for implementations which can cache the transformed results
of array data for reuse by several DrawArrays, ArrayElement, or
DrawElements commands. It is also useful for implementations which
can transfer array data to fast memory for more efficient processing.
For example, rendering an M by N mesh of quadrilaterals can be
accomplished by setting up vertex arrays containing all of the
vertexes in the mesh and issuing M DrawElements commands each of
which operate on 2 * N vertexes. Each DrawElements command after
the first will share N vertexes with the preceding DrawElements
command. If the vertex array data is locked while the DrawElements
commands are executed, then OpenGL may be able to transform each
of these shared vertexes just once.
* Is compiled_vertex_array the right name for this extension?
* Should there be an implementation defined maximum number of array
elements which can be locked at a time (i.e. MAX_LOCKED_ARRAY_SIZE)?
Probably not, the lock request can always be ignored with no resulting
change in functionality if there are insufficent resources, and allowing
the GL to define this limit can make things difficult for applications.
* Should there be any restrictions on what state can be changed while
the vertex array data is locked?
Probably not. The GL can check for state changes and invalidate
any cached vertex state that may be affected. This is likely to
cause a performance hit, so the preferred use will be to not change
state while the vertex array data is locked.
New Procedures and Functions
void LockArraysEXT (int first, sizei count)
void UnlockArraysEXT (void)
New Tokens
Accepted by the <pname> parameter of GetBooleanv, GetIntegerv,
GetFloatv, and GetDoublev:
Additions to Chapter 2 of the 1.1 Specification (OpenGL Operation)
After the discussion of InterleavedArrays, add a description of
array compiling/locking.
The currently enabled vertex arrays can be locked with the command
LockArraysEXT. When the vertex arrays are locked, the GL
can compile the array data or the transformed results of array
data associated with the currently enabled vertex arrays. The
vertex arrays are unlocked by the command UnlockArraysEXT.
Between LockArraysEXT and UnlockArraysEXT the application
should ensure that none of the array data in the range of
elements specified by <first> and <count> are changed.
Changes to the array data between the execution of LockArraysEXT
and UnlockArraysEXT commands may affect calls may affect DrawArrays,
ArrayElement, or DrawElements commands in non-sequential ways.
While using a compiled vertex array, references to array elements
by the commands DrawArrays, ArrayElement, or DrawElements which are
outside of the range specified by <first> and <count> are undefined.
Additions to Chapter 3 of the 1.1 Specification (Rasterization)
Additions to Chapter 4 of the 1.1 Specification (Per-Fragment Operations
and the Frame Buffer)
Additions to Chapter 5 of the 1.1 Specification (Special Functions)
LockArraysEXT and UnlockArraysEXT are not complied into display lists
but are executed immediately.
Additions to Chapter 6 of the 1.1 Specification (State and State Requests)
Additions to the GLX Specification
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GLX Protocol
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INVALID_VALUE is generated if LockArrarysEXT parameter <first> is less
than zero.
INVALID_VALUE is generated if LockArraysEXT parameter <count> is less than
or equal to zero.
INVALID_OPERATION is generated if LockArraysEXT is called between execution
of LockArraysEXT and corresponding execution of UnlockArraysEXT.
INVALID_OPERATION is generated if UnlockArraysEXT is called without a
corresponding previous execution of LockArraysEXT.
INVALID_OPERATION is generated if LockArraysEXT or UnlockArraysEXT is called
between execution of Begin and the corresponding execution of End.
New State
Get Value Get Command Type Value Attrib
--------- ----------- ---- ------- ------
ARRAY_ELEMENT_LOCK_FIRST_EXT GetIntegerv Z+ 0 client-vertex-array
ARRAY_ELEMENT_LOCK_COUNT_EXT GetIntegerv Z+ 0 client-vertex-array
New Implementation Dependent State