From: John Wann <john1@HMS01.HMS.UQ.OZ.AU>
Subject: Re: TECH: Sega HMD info

 Bernie Roehl cross-posted (from Allan Pratt)
> Today (8/30/93) I experienced the Sega Genesis VR game. It 
> was in the context of a test conducted by Stanford Research 
> Institute (SRI) for Sega.

It was great to hear that someone has actually seen this mythical 
head-mount.  But now I would stress some caution on the 
interpretation of data about its (visual) performance.  It is not the 
case that HMDs cause visual stress, but this may be produced 
through a combination of an HMD's physical characteristics and 
what is then displayed on the screens.  

If, as reported in this "peek", the software merely presents a 
typical battle-zone game in far-space where "The distance effects 
were never very convincing or useful", then we would predict 
that there may only be very minor stress placed on the visual 
system.  -  So the SRI testing may come up with null results (e.g. 
nothing much happens to vision).  This does not mean, however, 
that such HMDs are safe for unrestricted home use.  If an 
"asteroid" game is then released, where you steer through a 
maelstrom with chunks of virtual rock whizzing past your ears 
then the stress placed on the vergence system may be 
considerable (e.g. accommodation vs disparity cues).  Hence any 
testing should not be based on what software is currently 
available, but through the full range of virtual space that it is 
possible to reproduce.  If problems are observed it may then be 
possible to limit these by limiting the degree of disparity 
produced conflict in any future software development.

These comments also apply to the effects of tracker lags.  If the 
device has inherent lags in its peripherals, it is necessary to 
anticipate, or find sensible limits on the use of head motion in 
more advanced games.

John Wann
Edinburgh VR Project