From: daver@sunspot.ssl.berkeley.edu (David Ray) Subject: Re: TECH: Ultrasonics, parallel processing, HMDs, etc. Date: 7 May 1992 00:30:02 GMT Message-ID: Organization: /etc/organization In article <1992May5.222002.14189@u.washington.edu> thrusher@shelley.u. washington.edu (James Thrush) writes: >..(stuff deleted).. >1) How widely used are ultrasonics in VR? It seems to me that >ultrasonics is the easiest, cheapest way to obtain 3D telemetry. I >know the PowerGlove uses this and I was wondering also whether echoing >is a problem. Echoing IS a problem, at least with the Power Glove. It is a cheap setup (sticker on mine said $39.95) so it is quite possible that a more robust circuit could eliminate it. Some people have gotten around the problem by writing code that throws out erroneous data, however you lose speed and consistent clocking when that happens. I'm more of a hardware person than a programmer, and I'm using prewritten software that I don't want to mess with. Ideally you want to get rid of the noise, not program it out. I found that most noise can be eliminated by operating the PG in a large room, away from walls, or by putting ultrasonic absorbing material behind it. Egg crates don't work so well, corrugated foam packing material works better, and real engineered anechoic foam works the best. I found a supplier of good anechoic foam, a 4'x 4' piece goes for about $40. With the good foam, I get virtually NO noise when using it in a very small room (6x10 ft). Dave