VMD-L Mailing List

From: Michael Redmond (redmond_at_engr.wisc.edu)
Date: Fri Jan 24 2003 - 14:43:16 CST

John,
I actually do use that command when running scripts, but I usually hadn't
included it in the .vmdrc unless I was scripting a specific demo with
Windows (at least my current Windows version of VMD does not read scripts).
So I know how to do this and, for now, that is a reasonable solution. I can
probably even script it to come up with 0.0 eye separation, so to get
stereo, I would just need to increase that.

The NVidia Windows drivers have an option to sync to vertical. I have tried
to set it but to no effect. It turns out that I use the cheap eDimensional
"in-line" shutter glasses (about $70), and the image shearing initially
caused them to lose sync (every 12 seconds, there would be 6 "open shutter"
glitches 2 seconds apart that corresponded to the shearing). eDimensional
has a resync utility that I assume finds a good sync period and then forces
the glasses to ignore signals that are outside that period (not sure, but
that's how I would do it). This clears up the "open shutter" flashing of
the glasses, but the image shearing is still there. Again, this is on our
550XGL card (real cheap stereo at $250 or less). Out 900XGL also exhibits
shearing, but it is harder to spot (for us, on one periodic shear in the
top 10% of the screen - can't test with "in-line" glasses because the DVI
connector/VGA adapter is not compatible with the eDimensional
dongle/connection).

So, it appears that the NVidia driver recognizes the need to vertical sync
and then, for some reason, doesn't actually do it. That's my speculation
anyway...

This problem does not show up with clone mode (not too surprising). In our
initial tests, it also does not appear to show up under Linux with the same
shutter glasses. So someone at NVidia knows how to fix it. Interestingly
enough, other glitches have show up with Linux stereo, though not yet fully
verified. If you go to full-screen mode in stereo on one of our Linus apps
(CEI Enliten), one of the buffers gets corrupted. On the Windows side,
full-screen openGL stereo (not in a window) also messes up. We can't run
full-screen stereo Cortona as a result.

Lots of gotchas in the NVidia driver and/or hardware implementation still.
Too bad...

Thanks
Mike 

---
At 02:18 PM 1/24/2003 -0600, John Stone wrote:
>Michael,
>   You can force VMD to go into stereo mode by default by adding this
>command to your individual .vmdrc (Unix) or vmdrc (Windows), or for all
>users that run the program by editing the core VMD startup script and
>adding it to the end:
>   (install dir)/vmd/scripts/vmd/vmdinit.tcl
>
>Here's the command to enable stereo:
>   display stereo CrystalEyes
>
>You can enable one of the other stereo modes as well by default, choose
>whichever fits your use the best.
>
>Interesing that you mention their screen tearing problem.
>Do you have the driver set to force syncing to the monitor's vertical
>retrace/blank?  (does their driver do that by itself?)
>
>If you do stereo without forcing sync to vertical retrace you will get
>all kinds of screen tearing.  I assume that their driver would do this
>by default when its running in a stereo mode however.
>
>Regarding the "clone mode" stereo.  This can be done with any normal
>stereo capable system with one of the CyViz stereo splitter boxes.
>They are expensive, but they'll do it generically for any workstation or
>PC card with stereo outputs.  I know that this sort of thing can also be
>done on some of the high-end Unix systems.  As far as PC's though,
>yeah, NVidia's cards are probably the only ones that will do that
>presently, at least as far as I know.
>
>   John Stone
>   vmd_at_ks.uiuc.edu
>
>On Fri, Jan 24, 2003 at 01:54:26PM -0600, Michael Redmond wrote:
> > My workaround in VMD has always been to immediately go to stereo mode 
> after
> > starting the program. I don't know if there is a command line option to
> > start in stereo mode. In VMD this isn't a big deal, but some other apps
> > (Ensight by CEI in our case), it is a hassle to make have scripts 
> include a
> > stereo command before doing anything else. All operations are slowed by 
> the
> > mono performance hit because of slow image update speeds.
> >
> > The NVidia cards are also giving me problems in shutter glasses mode (only
> > under Windows at this point) in that the image "shears" at periodic
> > intervals (6 shears 2 seconds apart followed by stable image for 12
> > seconds...this with 120Hz refresh and any type of shutter glasses on
> > 550XGL). It is a noticeable glitch but one that we are living with for 
> now.
> > Hopefully NVidia will fix it if they first will acknowledge it is an 
> actual
> > problem (or undocumented feature I guess).
> >
> > Since I work with clone mode stereo for dual projector passive stereo
> > display, the NVidia cards appear to be the only choice. I haven't seen 
> this
> > feature in other cards yet.
> >
> > Thanks for the input. I sent John's message on the the PNY/NVidia folks 
> and
> > hopefully something will come of it.
> >
> > Mike
> > ---
>...
>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
>   WWW: http://www.ks.uiuc.edu/~johns/      Fax: 217-244-6078