Re: passive stereo on Onyx2-IR

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Angus Dorbie (dorbie++at++sgi.com)
Tue, 06 Jul 1999 14:22:24 -0700


Passive stereo can use color masking or multiple projectors and
polarizing filters. There is another cool temporal method which uses
ploarized shuttering over the display and passively polarized glasses.

You asked specifically about color glasses an this is easy, you just
need two overlapping channels and appropriate glColorMask calls in the
channel draw callbacks. Obviously the quality is better if you can use
polarizing methods and multiple overlapping projectors but that depends
on your display environment.

The main compromise with the color masking is color reproduction, and
some colors produce zero contrast in one or other eye. Monochrome
rendering is really the only easy option.

Polarizing is better and you only really lose some brightness, 50% or
25% depending on shuttering vs multiple projector approach. It costs you
for the extra projector (or shutter) and channel, and you either need
more framebuffer area or quad buffering (stereo visual) depending on the
chosen method (but on iR it's practically free if you only start with 1
channel, the rendering cost is obviously there for all methods) and the
shuttering approach will be line rate constrained for the monitor. I've
only seen the shutter used in a Tektronics demo years ago, I'm not sure
where you'd obtain a polarizing shutter today and don't know if you
could easily sync it to the stereo vof as you can crystal eyes LCD
emitters. It was such a cool idea somebody must be doing it.

Cheers,Angus.

k. lukose wrote:
>
> Can someone offer any information on "passive" stereo viewing on an Onyx2-IR.
> By this, I mean a system where the left and right eye images are *superimposed*
> (rather than flashed alternately) on each frame, each in a different color. The
> viewer resolves the image by viewing the screen through correspondingly colored
> (and very cheap) eye-glasses - similar to entertainment 3D movies.
>
> The questions are:
> - is this at all possible?
> - what are the software tools needed to put one together?
> - what are the resulting compromises in visual fidelity?
>
> Thanks.

-- 
For years now, whenever NT has been proven to have some debilitating
weakness we've heard from MS advocates that NT would catch up, there was
just an incredible faith in this OS and Microsoft's ability to somehow
get there. With the recent results of the Linux vs NT serving benchmark
that same attitude can be seen in the Linux community. The Linux folks
aren't too worried, "Sure the single threaded IP stack was slow but
it'll be fixed in the next release.", it's eerily familiar but I have
confidence in the Linux community's ability to remedy problems and I
don't groan in pain as I used to when Microsoft made similar claims.

For advanced 3D graphics Performer + OpenGL based examples and tutors: http://www.dorbie.com/


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