VMD-L Mailing List

From: John Stone (johns_at_ks.uiuc.edu)
Date: Wed Apr 30 2003 - 20:45:29 CDT

Hi Marc,

On Wed, Apr 30, 2003 at 09:43:58AM +0200, Marc Baaden wrote:
> I do also see something that corresponds quite well to your description
> of an occasional "glitch". It is very annoying, and it is like you swap
> from a mode with fine stereo to a mode where left and right eye are not
> properly represented and you cannot see real stereo.
>
> I just wonder if that is a problem with
> - nvidia driver

Yes. The driver or else the hardware itself.

> - stereo shutter / video driver synchronization

Unlikely, if so, this would be a hardware or driver problem again.

> - VMD ( I guess not .. ? )

No, VMD has been working fine with quad-buffered stereo for many years now.
Many people use it regularly on Suns, SGI, Windows, and other platforms
without any of the troubles people have described with the Quadro boards
recently.

> - high load on the machine

Irrelevant, if it has anything to do with it, then it is once again
a driver problem. The stereo buffer swaps would be done either automatically
by hardware at vertical sync time, or by software interrupt handlers in the
device driver code in the kernel. Either way, this also boils down to a
hardware/driver problem. There's really no excuse for losing sync other than
a driver or hardware problem.

> because for now it seems a lot more frequent when I run eg an IMD simulation
> on the same machine, eg when it is under high load.

Could be that Linux has bad interrupt handling characteristics when the
machine has a high load and lots of network I/O? This would still be a
device driver level problem in any case.

> Anybody else sees this ?
>
> The annoying thing in my case is, once it has gone clear for a frame, it
> does not immediately switch back to proper stereo. So you really can't
> use it when this happens.

I would strongly suggest making NVidia aware of this problem if they aren't
already: linux-bugs_at_nvidia.com
Its possible they might have a workaround for it, if not and its an actual
hardware problem, perhaps an exchange for a working card is in order?
Seems fair if the card was bought specifically for stereo usage?
Does anyone know if the cards have similar problems in Windows??

  John Stone
  vmd_at_ks.uiuc.edu

> redmond_at_engr.wisc.edu said:
> >> We just got our Stereo VMD working with Linux and Quadro 750XGL card.
> >> It is basically functional, but I am seeing the same types of
> >> problems I saw under Windows when using shutter glasses. It is very
> >> infrequent, but there will be an occasional "glitch" where both
> >> lenses of the glasses go clear for a frame (or maybe a few). I
> >> haven't detected the image shearing that is obvious with some Quadro
> >> cards (particularly the 550XGL) on Windows since the glitches are
> >> infrequent. On Windows, we end up correcting the problem with an odd
> >> resync utility that EDimensional has available on their web site.
> >> There is no equivalent for Linux and I am not sure what it does,
> >> though I expect it syncs the glasses to monitor refresh somehow.
>
>
>
> Marc Baaden
>
>
> --
> Dr. Marc Baaden - Institut de Biologie Physico-Chimique, Paris
> mailto:baaden_at_smplinux.de - http://www.marc-baaden.de
> FAX: +49 697912 39550 - Tel: +33 15841 5176 ou +33 609 843217
> 

-- 
NIH Resource for Macromolecular Modeling and Bioinformatics
Beckman Institute for Advanced Science and Technology
University of Illinois, 405 N. Mathews Ave, Urbana, IL 61801
Email: johns_at_ks.uiuc.edu                 Phone: 217-244-3349              
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