From: Wilson, Mark A (mark.a.wilson++at++lmco.com)
Date: 01/25/2000 04:37:26
The couple between IG channels is too tight to use UDP to
sync, especially since delivery is not guaranteed. DIS
employs time tags and dead reckoning in an attempt to overcome that
limitation resulting in well known discontinuities.
I'm fairly certain that simply tying sync signals together would
result in an unviewable image. Sync is sourced from the graphics card.
Imagine a monitor getting 3 unevenly spaced vertical syncs in a frame.
Most monitors wouldn't be able to display anything.
My first inclination is three PCs, each driving their own channel, and
a separate simulation host. Use a genlockable graphics cards to sync
vertical on all the IG systems. Use reflective memory (ie SCRAMNet) to
transfer data to and from the simulation host. This is not a low cost
solution (about $7500 per channel) but, it has a high probability of
success.
MaK has a demo of PC Stealth (not Linux Performer and not a general
purpose image generator) running three channels on a single PC.
If memory serves frame rate was in the 20Hz range. I believe they
were using 200SBs from Quantum3D.
Another, non-Linux Performer, solution might be XIG from CACI. They
had a pretty nice multi-channel demo is IITSEC this past December.
Mark A. Wilson
Advanced Simulation Lab
mark.a.wilson++at++lmco.com
407.356.6387
-----Original Message-----
From: KOHARCHIK++at++mcopn1.rsc.raytheon.com
[mailto:KOHARCHIK++at++mcopn1.rsc.raytheon.com]
Sent: Saturday, January 22, 2000 12:22 PM
To: info-performer++at++sgi.com
Cc: KOHARCHIK++at++mcopn1.rsc.raytheon.com
Subject: panoramic on Performer linux?
Hi folks,
We're looking for a way to draw a panoramic (120 degrees FOV) on
Performer using Linux. Our current system uses three monitors
positioned side by side in an arc, each displaying 40 degrees. If we
could drive three (or four) monitors and keep things reasonably well
synchronized, I think that would do the job. (Although I'm open to
suggestions about other display hardware too.)
I have heard some discussion about synchronizing multiple hosts
over UDP to say what to draw. I gather the consensus is that this
approach introduces too many artifacts to be satisfactory?
I've also seen a post about tying pins from different vga
connectors on differnt hosts together to coordinate vertical redraw.
Did I understand that right? Has anyone done it? I can see how that
would tell you when to draw, but how does that help you with what to
draw ? (Eg something on your scene may have changed and been picked up
by one host and not the other ones it's tied to by VGA sync so you end
up drawing different stuff, but at the same time.
One thing I haven't heard yet is talking about multiple graphics
cards per host. Can Performer or the Xserver split the scene over
several cards? Are there (I guess they'd have to be PCI) graphics
cards that have hardware acceleration for OpenGL?
One approach I've heard about is a program called MetaVR. I don't
know any details but my understanding is that they chain their systems
together through the parallel port to stay synched. Does anyone know
how that works?
Being new to this whole thing, I'm aware of how little I
know. Please feel free to correct my misconceptions and fill in the
gaps in my knowledge.
Regards,
gpk
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