overview of OpenGL
environment variables
Chapter 1 25
. This variable allows the user to specify the coordinate space to be used
for lighting. By default, HP’s implementation of the OpenGL will select
the lighting space. Possible values are:
HPOGL_LIGHTING_SPACE=OC
HPOGL_LIGHTING_SPACE=EC
where OC = Object Coordinates and EC = Eye Coordinates. For details
on the lighting space, see the sections “Lighting Space” and
“Optimization of Lighting” found in Chapter 5. This option is available
only for the HP Visualize fx family of graphics devices.
HPOGL_TXTR_SHMEM_THRESHOLD (HP Visualize fx family only)
This variable sets a fence for the use of process memory vs. shared
memory. Any 2D or 3D texture that has a size greater than or equal to
the threshold set is stored in shared memory. The initial value is set to
10241024 bytes. This variable should be set to the byte size desired for
shared memory usage. This option is available only for the HP Visualize
fx family of graphics devices.
new environment variables as of release 1.05
The performance of HP OpenGL double buffering has been improved for
Release 1.05 of HP’s implementation of OpenGL 1.1. With this
performance enhancement, there is a low probability that minor image
tearing may be visible during buffer-swap operations. The majority of
OpenGL applications will see no difference in the visual quality of double
buffering. However, this tearing may be noticed by some OpenGL
applications that render simultaneously to multiple windows. Two
environment variables can be set in an application environment to
control whether or not the new faster buffer swapping method is in
effect:
HPOGL_DSM_ENABLE_FAST_BUFFER_SWAP
When set to any non-NULL value, the new or faster double buffering
method will be used. (This is the default behavior and does not need to be
set except to override glHint as discussed below)
HPOGL_DSM_DISABLE_FAST_BUFFER_SWAP
When set to any non-NULL value, the old or slower double buffering
method will be used.
OGLImp.book Page 25 Tuesday, February 14, 2006 9:15 AM
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