From: "Bruce Cohen;;50-662;LP=A;" Subject: Re: rambling on motion Date: 12 Nov 90 17:59:21 GMT Organization: Tektronix Inc. On a cheaper note, the following idea came out of a conversation I had with Jim Kajiya of CalTech a couple of years ago. I'd been showing him the liquid-crystal shutter stereo display system on the Tektronix 3D graphics workstation, which prompted him to mention some work he wanted to do on the use of vertical parallax in depth cueing. He explained that he wanted to have the system detect the vertical position of the viewer's head with respect to the display screen center, then vary the eye-point of the picture to match, so that you see changes in parallax when you bob your head. This would not require stereo, but it would make stereo even more effective. We knocked around some ideas of how to detect the viewer's head position, and at some point we realized that the glasses we use for the stereo display were the answer. These are passive glasses, just polarizing filters, with the shutter over the screen, so the glasses are light and unobtrusive. But they do uniquely determine the viewer's head position and orientation. Rather than put a heavy Polhemus sensor on the glasses (and have to put the screen on the floor because no one could raise their head :-)) we thought about putting a reflective strip on the glasses, with some easily recognizable pattern, perhaps akin to the UPC bar code clock pattern. Sensing the pattern could be done by a camera but it might be even simpler to have a scanner like a check-out stand bar-code reader and a set of light detectors with half-silvered mirrors in front of them. The light from the scanner is split and sent to all the detectors, where it bounces off the half-silvered mirrors to go towards the viewer. The detector picks up the returned light, and its output signal can be convolved with the pattern on the reflective strip over one scanning frame to determine the angle of the line from the detector to the glasses relative to the zero point angle of the scan. Alternately scanning horizontally and vertically gives you a solid angle; Two detectors gives you triangulation for head position and tilt. -- --------------------------------------------------------------------------- Speaker-to-managers, aka Bruce Cohen, Computer Research Lab email: brucec@tekchips.labs.tek.com Tektronix Laboratories, Tektronix, Inc. phone: (503)627-5241 M/S 50-662, P.O. Box 500, Beaverton, OR 97077