Re: Stereo in a X Window

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Tom McReynolds (tomcat++at++proxima.asd.sgi.com)
Tue, 25 Jun 1996 17:55:27 -0700

On Jun 25, 3:49pm, Daniela Rainer wrote:
> Subject: Re: Stereo in a X Window
> Hi Tom,
>
> thanks for your help. I compared your code fragments with my OpenGL based
> Performer demo program and noticed that they are the same. The only
difference
> was, that I tried to run it in STR_BOT mode on a Indigo Extreme and this does
> not work. But on a Reality Engine it works with the Reality Engine stereo
> modes.
>
> Do you know what I have to do in OpenGL based Performer if I want to have
> stereo on a machine without quadbuffer stereo?

Good point. I may have been answering the wrong question. If you are doing
quadbufferred stereo, all you have to do is call glDrawBuffer() with the
back left buffer, draw the left eye view, call glDrawBuffer() again with the
back right buffer, draw the right eye view, then swap the buffers to get
the back buffers to the front.

If you are doing top/bottom stereo (aka full screen stereo), you have to
use the XSGI calls, and you'll have to synchronize the GL and X streams,
as other posters have pointed out.

The basic sequence for top/bottom stereo is:

glXWaitGL()
XSGISetStereoBuffer() /* left buffer */
glXWaitX()

draw left eye view

glXWaitGL()
XSGISetStereoBuffer() /* right buffer */

draw right eye view

swap buffers

Yes, it's slow, but it's unavoidable for top/bottom stereo; that's why
we don't encourage people to use this type of stereo. Quadbuffer stereo
is a much faster path, although it doesn't work with the older/lower-end
systems.

I don't have a top/bottom demo program at the moment, but I can point you
to an OpenGL program that does both quad buffer and top/bottom stereo.

The demo program is in the gl_dev.sw.samples ism in the IRIX 6.2 release,
and the program gets installed in

/usr/share/src/OpenGL/teach/stereo

I hope this helps...

        -Tom

>
> Best regards
> Daniela
>
> --
> ----------------------------------------------------------------------------
> Daniela Rainer
>
> rainer++at++rus.uni-stuttgart.de
> Tel.: ++49-(0)711-685-5970
>-- End of excerpt from Daniela Rainer

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