running OpenGL programs
virtual GLX (VGL) mode
Chapter 338
virtual GLX (VGL) mode
Virtual GLX (VGL) defines a special transparent mode within hp's
implementation of OpenGL that allows an hp client to render through
OpenGL to X servers and/or X terminals that do not support OpenGL or
the X server extension for GLX.
This mode is implemented by emulating the X server extension within
the OpenGL API client-side library and using the hp Virtual Memory
Driver (VMD) to perform Xlib rendering.
VGL provides flexibility for OpenGL users, but does not provide the same
level of performance as is available to servers supporting GLX.
visual support for the VGL mode
In VGL mode, the visual capabilities incorporated in
glXChooseVisual() and glXGetConfig() are synthesized from the list
of X Visuals supported on the target X Server and the capabilities of the
Virtual Memory Driver (VMD). Table 1-5 in Chapter 1 lists the X Visuals
that are supported through the OpenGL Extension to the X Window
System (GLX) in the Virtual GLX (VGL) mode.
special considerations
When you are in the VGL mode, you will notice the following differences
between it and the GLX mode.
• VGL deals with X servers that do not support replicated X visuals
that provide extended GLX capabilities. This results in a GLX visual
list that is synthesized from available X visuals. This list is assigned
the maximum set of capabilities supported by the Virtual Memory
Driver (VMD) for each particular visual. For example, if a visual is
found to be supported by the Double-Buffered Extension (DBE), then
it will be reported as having the capability of doing double-buffering.
Note that there will not be a counterpart for the GLX visual with the
same type and depth that is single buffered. Such visuals are locked
to either single buffer or double buffer mode, based upon the first
access. In VGL, to utilize one visual for both single and double
buffered operation, two separate X display connections must be
opened.
OGLImp.book Page 38 Tuesday, February 14, 2006 9:15 AM
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