From: Dick Rous (dick++at++sgi.com)
Date: 05/18/2001 07:57:33
hi dick. ok, but in a four wall cave, you don't necessarily use four
pipes- you use two pipes and 2 channels per pipe (right?).
You can indeed use 2 pipes and 2 (or 4 with stereo) channels per
pipe.
The important thing is, not to draw to more than one drawable per
pipe
(= Gfx board).
With one pfPipeWindow (abstracting the OpenGL drawable) and multiple
pfChannels (OpenGL viewports) you obey this rule.
similarly,
in a stereo app, you're rendering two contexts too - so, what i'm saying
i guess is that while i agree it's a performance hit it seems like it's
something that happens all the time as a necessary evil.
For stereo, use 2 pfChannels per display channel (eg. CAVE wall).
So, as an example, to display two CAVE walls from 1 pipe, create 1
pfPipeWindow per pipe and 4 pfChannels ( 2 left, 2 right) associated
2 by 2 to a physical (ircombine) channel.
As these pfChannels are merely OpenGL viewports, you avoid the
context
switch overhead you would incur by drawing into separate left and
right drawables.
So, it's not a necessary evil you cannot avoid. Just be careful when
designing your app.
i was wondering specifically how to do it - i.e. with what performer objects
and settings.
For an example how to implement stereo, look in
/usr/share/Performer/src/sample/pguide/libpf/C/stereo.c
Hope this helps,
regards,
Dick.
____________________________________________________________________
Dick Rous SGI - European Technical Support
email: dick++at++sgi.com
phone: +31-35-6423160 fax: +31-35-6423162 VNET: 955-6868
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"Doe iets, Tom Poes. Verzin een list." (Ollie B. Bommel)
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