Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!apple!sun-barr!decwrl!sgi!naegle@oberon.sgi.com
From: naegle@oberon.sgi.com (David Naegle)
Newsgroups: comp.sys.sgi
Subject: Re: Stereo viewing techniques
Summary: viewing non-stereo monitors with active stereo eyewear.
Message-ID: <41485@sgi.sgi.com>
Date: 9 Sep 89 00:15:44 GMT
References: <8909071236.AA15114@snow-white.merit-tech.com>
Sender: naegle@oberon.sgi.com
Organization: Silicon Graphics, Inc., Mountain View, CA
Lines: 48

In article <8909071236.AA15114@snow-white.merit-tech.com>, goss@SNOW-WHITE.MERIT-TECH.COM (Mike Goss) writes:
> [] It is sometimes necessary for the user of a stereo system to
> view other, non-stereo video monitors in addition to a stereo display.
> With active glasses, it is necessary to remove the glasses to view other
> video sources;  the glasses cause severe flicker otherwise.  With passive
> glasses, it is still possible to view other video sources without flicker.
> Also, if multiple stereo monitors are in use, active glasses require that
> all video monitors have synchronized refresh cycles in order to be viewed
> simultaneously; passive glasses do not have this requirement.

It is true that active eyewear will cause you to see slow-moving dark bands 
on a non-stereo video monitor.  That's why one of the four buttons on the
StereoView eyewear is a 'clear' mode button.  When you press this button,
you can look at non-stereo video screens with no problems.  Press it again,
and you're back in stereo mode.  This is somewhat less inconvenient than
actually removing the glasses, in most applications.

To deal with the situation where multiple stereo monitors are in use, 
the infrared transmitter is designed to broadcast a wide-angle pattern of 
stereo field (right/left) signal, and the glasses are designed to 'see'
a narrow pattern.  That way, the eyewear will lock onto the stereo signal of
whichever video display you're viewing at the moment.  

There *are* arrangements of monitors which can cause trouble, like trying
to view stereo on two unsynchronized monitors placed side-by-side, especially
from the maximum range. This arrangement puts the stereo transmitters too 
close together for the eyewear to lock onto one or the other reliably, 
since the angle of incidence is nearly identical for both I.R. beams.  
Usually, though, if you have to view multiple stereo screens at the same time, 
they can be arranged so that the I.R. beams don't come from nearly the same 
place.  Considering that it would cost $16K-$25K for two passive-eyewear
stereo systems to handle the rare instances which cannot be handled as
described above, most users would just do without stereo in those cases.

If you want theatre viewing, use a z-screen, or better yet, a polarizing 
stereo video projector.  StereoView glasses are meant for low-cost, one-on-one
applications.

> 
> ------------------------------
> Mike Goss
> Merit Technology Inc.
> (214)733-7018
> goss@snow-white.merit-tech.com

David Naegle
Graphics Hardware Manager
naegle@sgi.com