From: bobp@hal.com (Bob Pendelton)
Subject: Re: Low end VR
Date: Fri, 4 Oct 1991 18:43:57 GMT
Organization: HaL Computer Systems, Inc.


>From article <1991Oct1.193045.3213@milton.u.washington.edu>, by twkingsb@eos.ncsu.edu (TIM WINTHROP KINGSBURY):
> 

> In this news group, I have seen numerous discussions on how to create
> economical eyephones... But very little on how to create economical rendering
> to drive these HMDs when they are completed.  I was wondering what sort of
> approaches people had in mind for doing this.  I assume that when we say
> low-end virtual reality, we are thinking in terms of Macs, PC's and Amigas.

I assume the same thing.

> Without first achieving a reasonable frame rate, it seems like there is very
> little point in playing with home-made eyephones and Nintendo power gloves...

I think this all depends on what you expect to be able to do and see
with a low cost VR system. If you expect to see a detailed simulated
reality you are going to be disappointed. If you want to do
experiments in coordinating vision with hand motion, then PC based
systems with cheap displays will do nicely.

> Perhaps a better starting point might be to find a clever way to do some very
> fast rendering directly to the screen.

Define "fast." Define "reasonable frame rate." What scene complexity
do you want to deal with? Until we know what you expect, it is very
difficult to answer your questions.

For example, a 10 MHz 286 with an EGA card (my toy computer) using
TurboC++ can draw about a 1000 3d vectors per second. (Fixed point
arithmetic and no HLHSR (Hidden Line, Hidden Surface Removal).)

This means you can animate an "interesting" (50 or so vectors) object
at about 10 frames per second. The actual rate depends on how much
time you spend clearing buffers.

Faster machines can do more. Like I said before, what do you mean by
"reasonable frame rate," and "fast." What kind of scenes do you want
to render?

My personal opinion is that some valuable research can be done using
low end systems. But, I'm not going to try to fiddle around with head
mounted displays. If I want to see stereo images I'll draw the stereo
pairs on different sides of the screen and use mirrors or lenses to
bring the images together. (I rather like the idea of mounting
something like a ViewMaster a few inches from the monitor. I wonder if
it will work?)



			Bob P.

-- 

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