From: Harry Overs (hovers++at++dera.gov.uk)
Date: 01/25/2000 05:45:31
Why not stick two ethernet cards in each machine and send TCP/IP synch
pulses.
----- Original Message -----
From: "Wilson, Mark A" <mark.a.wilson++at++lmco.com>
To: <info-performer++at++sgi.com>
Sent: Tuesday, January 25, 2000 12:37 PM
Subject: RE: panoramic on Performer linux?
> 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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