Newsgroups: comp.sys.sgi
Path: utzoo!utgpu!news-server.csri.toronto.edu!me!ecf!drascic
From: drascic@ecf.utoronto.ca (David Drascic)
Subject: Re: Stereo wanted but no Crystal Eyes practicable
Message-ID: <1990Jul13.212623.19351@ecf.utoronto.ca>
Summary: build your own...
Sender: drascic@ecf.utoronto.ca
Organization: Dept of Industrial Engineering, University of Toronto
References: <1990Jul13.082301.813@urz.unibas.ch> <10323@odin.corp.sgi.com>
Date: Fri, 13 Jul 90 21:26:23 GMT

In article <10323@odin.corp.sgi.com> thant@horus.esd.sgi.com (Thant Tessman) writes:
>In article <1990Jul13.082301.813@urz.unibas.ch>, doelz@urz.unibas.ch writes:
>> Hi all, 
>> 
>> I need a stereo device for the power series which gives me an alternative 
>> to stereo view  (i.e., a shutter in front of the screen or similar) 
>> which enables me to let < 10 people look at a stereo image without 
>> nneding to spend 45000 SFr. for glasses. 
>> 
>> I'd appreciate any hints on source, implementation, and price/performance 
>> issues. 
>> 
>> Regards 
>> Reinhard
>> 
>
>StereoGraphics (415 459-4500) sells a thing called (I think)
>a Z-Screen.  It goes over the monitor and circularly polarizes
>every other frame.  The viewer wears passive polarized glasses
>that look like sunglasses.  This is the most economic solution
>for when you need to show a stereo image to many simultaneous
>viewers.
>
>The Z-Screen (or something like it) can be used with a projection
>television to create really big stereo images.
>
>thant

Another solution is to use several sets of active shuttering glasses.
Given the high cost of the Z-Screen, this might be something you want to
consider.

A few cheap options are:
- Sega sells some for their home video game system at about CAN$70.  They
  are encased in a cheapo housing with dark filters.  If you can change the
  spectacle housing you would probably be alot happier.
  The driver that comes with these is virtually unusable without the entire
  game system, so you'd have to build your own.  It's not too complicated.
- Haitex sells some better ones called XSPECS for the Amiga for about CAN$250.
  The driver for these glasses has a three connections, one for ground, one
  for +5V @ 33mA, and the third accepts TTL pulses to switch the glasses
  from the left-eye-open to the right-eye-open states.  It expects a 60Hz
  switching rate.

The limitation with these shuttering glasses is that they are all designed
to work at a 60Hz switching rate.  At this rate there is some preceivable
flicker, but under lower light level conditions, this is not a problem.

The Sega glasses can driven by the Haitex driver, which can drive two pairs
of glasses.

We use our Iris 3120 which has a regular 60Hz monitor to produce
stereoscopic graphics.  We use automatic colour table swapping to separate
the left and the right images.  By using some simple electronics to monitor
the sync signal to the monitor, we can make the Haitex driver switch the
glasses in sync with the colour maps, so that each eye gets only it's own
view.

The StereoGraphics system typically works at 120Hz, and is pretty expensive.
Our homemade system works at 60Hz, but is nice and cheap.

Hope this help!

	David Drascic
	Dept of Industrial Engineering, University of Toronto

	drascic@ecf.utoronto.ca
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