From: LHETTINGER@FALCON.AAMRL.WPAFB.AF.MIL Subject: Re: Motion Sickness and VR Date: Wed, 23 Jan 91 15:23 EDT It seems to me that there are four factors which have the capacity for causing motion sickness in V.R.: 1) Difference between perceived gravity and viewed "down." 2) Difference between perceived angular velocity and acceleration and viewed angular velocity and acceleration. 3) Perceived linear velocity outside of normal experience. 4) Difference between perceived linear acceleration and viewed linear acceleration. 5) Changes of direction at high speed. 1 and 2 are very easily solved. Just make the viewed orientation an accurate representation of the actual orientation. To turn, you actually have to turn your head; to tilt you actually have to tilt your head; the ground plane that you see remains true. I think you could probably get away with a lot here, such as putting a scaling factor between your real head's yaw velocity and your virtual head's yaw velocity. We are relatively desensitized to 3 when we are moving in the forward direction due to our experience driving or riding in cars. Forward motion is probably the easiest to which to become desensitized, as it carries no message that can be interpreted as "rotation." People who ride in trains a lot are probably desensitized to other directions of motion as well. However, I think it's probably a good idea to limit purely virtual motion to forward, for user interface considerations as well as perceptual ones. The concepts of walking and running are more easily understood than the cancrazan. 4 is tricky, but it may not be that much of a problem. Acceleration only need last until you get up to speed. Perhaps the disorientation can be minimized by choosing an acceleration so that getting up to speed is neither too abrupt nor too prolonged. If this is not sufficient, either viewed acceleration can be mapped through a scaling factor to actual acceleration (i.e. you have to walk forward to start accelerating, and stopping walking will only slow you down a little bit.), or acceleration can be triggered by tilting back the head, which emulates some of the sensations of acceleration. We might also be able to eliminate the need for such high perceptual speeds by compressing intervening space--do you really need to see every grain of sand in the Arizona desert when zipping from Phoenix to Tucson? I would personally like a set of virtual Seven League Boots. I don't know about 5, but I think that, as abrupt changes in direction at higher than brachiating speeds haven't yet contributed to much evolutionary pressure, this can maybe be ignored. If not, one could constrain the direction change to be gradual enough not to matter and require a slowdown before speedier direction changes. This would provide a nice kinesthetic parallel to driving an automobile. I think I'll go down to Disneyworld next weekend and do some research on Star Tours and the World of Motion, not to mention the Interstate. :-) Eric Pepke INTERNET: pepke@gw.scri.fsu.edu Supercomputer Computations Research Institute MFENET: pepke@fsu Florida State University SPAN: scri::pepke Tallahassee, FL 32306-4052 BITNET: pepke@fsu Disclaimer: My employers seldom even LISTEN to my opinions. Meta-disclaimer: Any society that needs disclaimers has too many lawyers.