Bernard Leclerc (bleclerc++at++cae.ca)
Tue, 1 Oct 1996 10:03:54 -0400
> With a single graphics pipe on your machine, I strongly recommend not to
> create multiple DRAW processes. Since you're using pf1.2 you won't be
> able to multithread the CULL stage as oppose to pf2.0
>
> If you've created multiple pfPipe's (one per channel), then your 3 DRAW
> processes will compete for a single resource (the graphics pipe) and
> force unnecessary graphics context switching.
>
> I don't recall Performer 1.2 API since I've been using 2.0 for more than
> a year now. However the principles are the same. With pf2.0 I would
> create a single pfPipe, open one pfPipeWindow and create 3 pfChannel's
on
> it. If the CULL stage becomes the bottleneck, use pfMultithread.
>
> Remember, you have a single pipe, you want to run at 30 Hz (33 ms) and
> you have 3 channels. It turns out each channel can use up to 11 ms max.
> But I would budget only 8 ms since you need spare time.
>
> Now, would you obtain better performance with Performer 2.0? I don't
> think so. Pf2.0 hasn't increased performance over pf1.2 - it improved
the
> API and added a lot of new functionalities. But performance wise, you
can
> expect the same result.
Chris Ege replied:
> We are also working on a project that will use three displays. Your
> reply worries us since we want 30fps. We are, however, going to be
> running it on an Infinite Reality Engine. What type of RE are you
> running your application on that gave you those performance results?
> If it isn't an IRE, would you expect a problem getting 30fps with an
IRE?
Chris,
You can expect better performance with the InfiniteReality (iR). I've been
working so far with the RealityEngine2 (RE2) but I had the chance to try
the new iR. However, it is still true that a single graphics pipe -
whether it's a iR or RE2 makes no difference - should be assigned only one
Performer DRAW process.
Now, answer these simple questions:
1- How many iR pipes do you have on your Onyx?
2- What is the resolution of your 3 channels?
3- How many CPUs do you have on your Onyx?
4- What type of CPUs are you using? R4400 or R10000?
If you have 3 pipes, then you should not worry. If you only have one pipe,
then the resolution becomes an issue. The higher is the resolution and
more likely you will be fill limited by the depth complexity of your
scene. But your lucky, the iR has Dynamic Video Resolution (DVR) to cope
with that problem. If you have enough CPU, you can also multithread the
CULL stage and obtain 3 culling processes, one for each channel.
The best solution is to have 1 pipe per channel. It's expensive but it
gives you a whole period of 33 ms to draw your scene. On the other hand,
the iR is much more capable than the RE2, and a single pipe could be tuned
to run 3 channels at 30 Hz. You might have to compromise the resolution,
but as I mentioned, DVR helps you anyway.
--
Bernard Leclerc CAE Electronics Ltd., 8585 Cote De Liesse
Technical Leader Saint-Laurent, Quebec, Canada, H4L-4X4
3-D Graphics Applications tel: +1 514 341 2000 extension 2275
bleclerc++at++cae.ca fax: +1 514 340 5496
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