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From: dbs@speech2.cs.cmu.edu (David Sanner)
Newsgroups: sci.virtual-worlds
Subject: do-it-yourself "verminals"?
Message-ID: <10709@milton.u.washington.edu>
Date: 7 Nov 90 00:02:15 GMT
Sender: hlab@milton.u.washington.edu
Organization: Carnegie-Mellon University, CS/RI
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  hi again,

( maybe this belongs on sci.electronics, but i thought i'd post it here first)

   some time ago, a couple folks posted some messages on their steps
 towards 'homebrew' virtual reality systems.  unfortunately it seems to
 have stalled, for the moment.
   i'm interested in starting a thread in this group for people who either
   1) have developed their own systems, or
   2) are interested in developing them.  
 i fall into the latter category.  i have a lot of ideas, and i'm 
 currently working on the software end... i need help, though, putting 
 together the hardware end:

   sure it won't be fast.  i don't care.
   sure it will have lousy resolution.  i don't care.
   sure it will be buggy.  i don't care.

   i think many issues in VR can be explored with a "cheap", do-it-yourself 
 "virtstation" (or, if you prefer, "verminals"!)

   as i mentioned, i'm primarily interested in what people are doing, or 
 are thinking of doing, with the hardware end of things.. ( i.e. all those 
 great input/feedback devices).
   ultimately, the system should allow a user to be able to walk, sit
 turn head, etc. with the appropriate feedback.  the system should also be 
 able to be built by anybody with a soldering iron, determination, and a 
 meager amount of cash.  that is, perhaps, way too ambitious at the moment... 
 but it's something to shoot for (remember, it doesn't have to be perfect!)
   as for the software 'visualizations', i'm keeping my pie-in-the-sky 
 ideas in check, at the moment.  just some 3d polygons or lines, updated 
 in (mabe) real-time response.  then i'll go from there.

   let me start it off:
   
 [to get the greatest possible use of available equipment, lets assume i have
 a room which can be more or less used for VR alone.  this might allow us to 
 consider less flexible systems (like, wall mounted tracking systems, etc.)]

   i have an amiga 1000.  ok, it's anchient, but it still works, and i've
 hopped it up to 2.5megs and a 20MB harddrive.  i'm just pounding out the
 code for 3D at the moment.  the code should be done soon (and the check is
 in the mail...) and i'm looking toward the next step.  
   for visual feedback, i'd like to do the following: take 2 2.7 inch b&w
 sony watchmans (or similar device), and rip them apart.  mount the ntsc
 circutry on a backpack/chestpack/tether.  mount the screens on an old 
 motorcycle helmet at the appropriate angles.  for sound, insert some 
 thin earpieces into the helmet, and connect to the amiga.  for a locating
 device, well... some people have mentioned an electronic compass
 (like the 'shack has) - hopefully, using "flux-gate" technology, the influence
 of stray magnetic fields (like those in a normal house, or around elec. 
 circuts) can be decreased (any one care to mention how this works?).  
 this can be mounted on the helmet, and the data fed into the computer.  
 when (if!) the data-glove rs232 version comes out, mabe it can be used in 
 a similar manner (the sonar method the power-glove uses seems so limited...)
   now, several things rule this choice: black and white watchmans are
 cheaper than color.  my amiga outputs a TV signal.  the helmet is no longer
 useable on the road.  the amiga has stereo sound outputs.  the electronic 
 compass is cheap, and with schematics, you might be able to build your own.
 provided, of course, that it can produce stable output in the presence of 
 normal magnetic fields produced in a normal house (and circuts). 
   notice that all these things spell 'cheap', 'cause i'm poor.  as i 
 mentioned, i'd like to keep the approach as cheap as possible (and that
 would be an accomplishment in itself !!)
   major flaws are apparent in this system.  for instance, i'd need 2 amigas,
 or switching/buffering circuts to use the ntsc outputs, to get 2 seperate 
 pictures on the watchmans.  but i think the visual part is doable (since
 some folks out there have already done similar things).  the elec. compass
 may work ok in a level plane (parallel with the ground), but what happens 
 when you incline your head forward/backward... and does it have a settle 
 time before it's output is valid?  how do you detect someone lowering or
 raising themselves in altitude?  etc...
   naturally, there are lots of alternatives to the design. since i've assumed
 i have a whole room at my disposal (well, a basement), i could mount sensors 
 on the wall, and have some kind of receptor on the helmet.  or, since the 
 helmet encases the whole head, some kind of mechanical/electronic marriage
 may provide adequate response (e.g. a linkage assembly attached to the 
 back of the helmet, and also to your back.  motions of the helmet are 
 translated as relative motion to your (assumed straight) back).

   anyway, i'm hoping the rest of you will pick out problems or suggest
 solutions of your own, and hence a new thread of discussion...
   
     thanks,

    ... dave sanner
        dbs@speech2.cs.cmu.edu