From: langston@memstvx1.memst.edu (Mark C. Langston)
Newsgroups: alt.cyberpunk.tech
Subject: Re: TV glasses and VR
Date: 11 Nov 92 00:35:31 -0600
Distribution: world
Organization: Memphis State University

In article <qqeXTB2w165w@freeside.com>, popec@freeside.com (PopeC) writes:
> Depends on the interfaces.  For VR you need a left and a right channel to 
> really work right as each may be a little different.  If these glasses 
> have only one interface feeding two screens, this may be a problem.
> Converting a VGA display to NTSC isn't a real big trick.  There are 
> boards of the shwlf now that do that.
>   Once again, you need two boards, one left, one right to give you true 
> stereoscopic viewing.  
>   Hacking these things to work for true stereoscopic VR may be a bitch.
> Maybe they'll be smart on the Glasses and make a VR ready pair for VR 
> hackers.  

  Well, I don't see it as being all that hard (or expensive).  It'll just
require a little imagination.

To begin:  I haven't seen the article, but I'll assume for sanity's sake the
tuner is not an integral part of the frame (read: it's a belt-pack, pocket-
stored walkman-type thingie, or similar).  Well.  We don't need a tuner, so
bye-bye unnecessary hardware.  This leaves us with two very small, very
useable video displays with appropriate inputs (throw a few things here and
there if you want to get nice and have modular input jacks, either digital or
RGB for each vidmon.

  Okay.  We've got the raw device now: a cheap hmd without directional feedback
...so what next?  No need to get fancy.  Just hack some code into whatever
image driver you're using for the VR, so it alternately renders a full view,
first right eye, then left, with appropriate perspective (not much,  if the
mon's are sitting 1" or so from your face...a little goes a long way...in
fact, a general algorithm could probably be developed here).
  Now then.  What do we have now?  A computer generating scenes very quickly
at alternative perspectives.  Result?  A mess of jittery images on your
monitor.  Now what?  Simple.  Throw the output to _both_ mon inputs, and wire
up a simple circuit that's gonna alternately pass the vid signal to one eye
at a time.  Get fancy:  Use the digital output of your computer, sync the
switching to the comp's refresh rate (sync line avail on digital signal out
of computer).  What do you have now?  Homebrew VR.

A problem with images too flickery to be of any use?  Not.  I am assuming
a) that the displays are LCD, so the decay rate of the display is going to
be longer than the refresh rate of your comp vid out signal (although
hopefully not so much longer that you lose updates), and b) your comp refresh
rate is high enough to be of practical use anyway.  

Hook up a Powerglove (get creative...use two!), and you're off (or in?).

Get even more creative:  Add analog joystick mechanisms as directional feedback
for the almost-full HMD.  I'll leave this as an exercise for the reader.

Have fun.  Get lost.


-- 
+--------8<------Cut Here------8<------Cut Here------8<------Cut Here---------+
  Mark C. Langston   |  "Secrecy is the beginning of tyranny."                 
  Psychology Dept.   |  "Always listen to experts.  They'll tell you what can't
  Memphis State U.   |     be done, and why.  Then do it."                      
      "Pftph!"       |           -From the notebooks of Lazarus Long