From: Robin Hollands Subject: Re: TECH: How does a source-less tracker works ? Date: 1 Mar 1996 14:42:32 GMT Message-ID: <4h72co$5f1@bignews.shef.ac.uk> Organization: Automatic Control & Systems Engineering, University of Sheffield From: Robin Hollands >I need your help. I'm working on my graduation paper and I'm just >trying to describe VR-Systems and their components. I can't find >anything about "source-less tracker" (like in Forte's VFX-1 System) > I wrote an article on this as part of VR News' excellent Technical Reviews last year. There are a number of different technologies, but the most commonly used is the gravimetric device. This simply uses a 2-axis (fluid filled) tilt sensor for measuring pitch and roll with respect to gravity. To measure yaw (or heading) an electronic compass is used. The Cybermaxx and i-glasses! use trackers licensed from Precision Navigation, who specialise in this technology. Forte developed their own for the VFX and then sued VictorMaxx and Virtual i-O! Another technology used is inertial techniques which primarily use gyroscopes, but can also use accelerometers. A UK company, VR Systems UK market a gyroscopic based orientation tracker, primarily as an input device for disabled users. Another company, started by Eric Foxlin, has produced a high precision tracker based on similar techniques that can also be used in a hybrid mode. Another technology being investigated uses a inside-out camera system and measures optical flow of the surroundings, and I've also heard of another company developing a full 6DOF sourceless system, but they hadn't been cleared to reveal the technology. For a fuller description of the technologies, and a survey of currently available devices, see my article in VR News. Contact mike@vrnews.demon.co.uk for back issues. Cheers, Robin (UK Vr-SIG Chairman)