From: jpc@tauon.ph.unimelb.edu.au (John Costella) Subject: Re: HARDWARE: hand tracker idea Date: Fri, 16 Apr 93 17:45:28 EET > Is there some reason that all these glove makers are sensing > each joint? Isnt all we need to know is where each fingertip > is? A polhemus like transmitter on the last joint of each > finger (and maybe one on the wrist)should do the job. If only > polhemi were cheaper. Can we use more than one transmitter? > How about mechanical methods to detect the position of the > fingertips? I have thought of a few lo tech ideas already. It comes down to signal-to-noise. If you measure a la Polhemi then you are measuring *absolute* position relative to the lab. You have to do this accurately enough (millimetres?) to make any use of it. You then subtract the three-position of the wrist to get relative finger position (relative to rest of hand). Measuring a la a glove, you are obtaining a *relative* position directly---which is what you actually want for the finger gestures. You then look at the noise levels: finding the small difference between two large signals boosts the signal-to-noise ratio by the same factor. On the other hand (sorry, no pun intended), a glove method will yield you relative positions directly, so the SNR is just that of the device. In *principle*, if there were very accurate absolute position transducers that were cheap, and only lousy glove-based transducers that were very expensive, then you'd be right: you'd be better off using the absolute position transducers (as long as you had at least 10 spare channels!). But (barring revolutionary transducer inventions) that's not the case right now. You also have to be prudent in your use of wireless forms of transducer: you must use different parts of the electromagnetic or sonic spectrum for each transducer channel! John ---------------------------------------------------------------------------- John P. Costella School of Physics, The University of Melbourne jpc@tauon.ph.unimelb.edu.au Tel: +61 3 543-7795, Fax: +61 3 347-4783 ----------------------------------------------------------------------------