Dave Pape (pape++at++evl.uic.edu)
Thu, 5 Mar 1998 20:41:57 -0600 (CST)
We've recently started running our Performer apps on a 4 pipe
Onyx2/IR, and noticed a disturbing drop in framerate as more pipes
were used. It appears that Performer is serializing the draw
processes when the Onyx is in a TKO-style configuration (pipes
are displays :0, :1, :2, and :3).
To verify this, I added some code to get timestamps at the beginning and
end of the channel draw callback (which selects the stereo buffer, calls
pfClearChan() and pfDraw()) on certain frames, and printed them later.
The timing information clearly showed that the pipes were being drawn in
sequence, rather than in parallel.
On a wild guess, I switched the system to single keyboard mode (:0.0,
:0.1, :0.2, and :0.3). With just this change, the draw stages for the
different pipes now all start at the same time, and the framerate is
back to what we'd expect.
These tests were run with Performer 2.2 n32 and o32, and Performer 2.1.3
o32. All three versions had the same behavior. We're using Irix 6.4.
So, what's the deal? Is there something I might be doing, or not doing,
which would cause this? (all the channels are attached together, and share
the scene, draw func, and swapbuffers) Is it a Performer bug, and is
there a fix?
-Dave
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Dave Pape Electronic Visualization Laboratory, UIC
pape++at++evl.uic.edu http://www.evl.uic.edu/pape/
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