From: mbernat@gel.ulaval.ca (Marc Bernatchez)
Subject: Re: INDUSTRY: New VR Display Classes, etc.
Date: Sat, 24 Aug 96 15:05:21 GMT
Organization: dep. de Genie electrique


>***********************************************************
>Organizer: Ed Lantz of Spitz, Inc.
>Panelists:  David Bennett of Alternate Realities Corp., Bertrand de La
>Chapelle of VIRTOOLS, Steve Bryson of MRJ/NASA Ames, David Zeltzer of MIT
>Research Lab of Electronics, and Mark Bolas of Fakespace
>
[...]
>
[...]
>
>Mark Bolas dissented from calling a non-stereoscopic display "VR."  I
>personally disagree, as stereopsis only provides highly useful 3D cues
>in applications where near-stationary objects are being manipulated at
>close range (admittedly, alot of VR applications do this... but not
>all).

I must go with Mr. Bolas opinion here. A high level VR system must be
immersive. In turn, immersion is highly influenced by the use of
stereoscopy.  You can hardly say you have the feel of being there, or
that you are close by an object, if you can't "feel"(read see) your
hand is near it... All this require close by spatial cues which are
best rendered using stereoscopy. So yes, highly VR systems must use
stereoscopy to my point of view.

Notice that I have used a level of VR reference using the term "high
level VR". What this means is that a system can be ranked anywhere on
a continuous range from non VR at all to fully VR. You can't, in my
opinion, give some systems the "VR tag" and not the others. Remember
the VR.5 thing? It may have looked a bit silly or strange but I read
an interesting text they had made for it. They were trying to describe
like 6 or so VR levels. from a basic 3D CAD with no VR at all to the
fully equipped HMD and glove thing. This is a good way to aim at I
think.

This is the kind of debate we will have in the upcoming VR Live
conference I have announced in this group earlier. If you are
interested in this...join in the first Saturday of September. (sorry,
had to plug it ;-)

>  Other 3D cues including motion parallax/shear, object rotation,
>shading, depth cues such as fog and object size, etc. are very
>effective and can create the illusion of 3D immersion when employed in
>a SID.  Also a SID provides, by definition, accurate angular
>(look-angle) representation of the VE, a very strong spatial
>navigation cue.  Stereopsis is hardly useful at all when flying over
>terrain at a distance, or for fast moving objects.

On some occasions, fast moving objects can greatly benefit from being
stereoscopic in the VR world. You can stay tuned to the stereo effect
for quite fast movements in fact.

>  Add the eye strain
>factor of conflicting cues (vergence vs accomodation), the hassle of
>eyewear, etc. and you will find that many venues will not want to
>bother with a stereoscopic SID.

Yes, there are indeed some concerns about these conflicts but if well
designed and used, you can minimize these side effects to a point
where they don't show up on users... even if they stay in immersion
for a long period (like an hour or two).

I have written a short essay about these concerns. It's on VResources
in the articles section if you want to read it.

>In my opinion, one of the most important outcomes of the panel was the
>adoption of a third general VR display class: the Virtual Model
>Display or VMD.  This includes the ImmersaDesk(tm), the Virtual
>Workbench, and the Responsive Workbench which are best suited to
>representing 3D object models rather than fully immersive workspaces.
>Although varying degrees of visual immersion can be obtained in
>flat-screen desk-type displays, these displays really shine when a
>model such as a human body is displayed in its entirety.  Here there
>is no need to create a "sense of presence" within a room.  Rather, as
>Bertrand de La Chapelle put it, the model "emerges" from the display
>rather than the user being "immersed."  Thanks to Steve Bryson,
>working with Mark Bolas, for coining this new display class.

Isn't that what we call desktop VR? The term desktop VR has been used
for quite some years and is a system where you use such a PC display
with LCD shutter glasses to get the stereoscopic effect. You can also
uses sets of mirrors and lens with a split screen configuration. The
way you use to show an object come out the screen isn't important in
fact.

To finish, I will say that I strongly believe that the SID based
systems have a great future in the VR field... at least as long as we
can't produce better HMD systems that won't have the actual
bottlenecks. I will soon add this new term to the "VR Term" glosary
now found on VResources.

Very interesting text you posted Ed, thanks


 Marc Bernatchez             |  E-mail: mbernat@gel.ulaval.ca
 C.O.P.L. (local plt-00307)  |============================================    
 Dep. Genie electrique       |  http://www.gel.ulaval.ca/~mbernat
 Universite LAVAL            |  http://www.imaginative.com/VResources
 Quebec, Canada              |============================================
 G1K 7P4                     | Virtual Reality is the future of computers