From: james@wet.UUCP (James Marshall)
Subject: Very cheap head tracker, using spring-fed fishing line, maybe?
Date: 9 Dec 91 23:25:15 GMT
Message-ID: <3140@wet.UUCP>
Organization: Wetware Diversions, San Francisco



I don't know if this has already been tried, but here's maybe a short-term
solution.  It only works for a short range, and you can't turn your head
all the way around (a la "The Exorcist"), but it might be usable until we
get a workable and cheap high-tech solution.  The method is:

On the top of the helmet, put (let's say) three hooks in a ~4 inch triangle.
At the top of your range of movement (like your ceiling), in the corners,
mount little spring-fed fishing line feeders.  Same concept as a spring-fed
tape rule.  The line feeders should be able to measure "amount of line fed
out", for one dimension of input.  Then, you guessed it, attach the fishing
lines to the hooks in the helmet.  This provides as many dimensions of input
as you have line feeders; you then have lots of defined polygons to work 
with.

The theoretical minimum is six lines attached to your head, using at least
three helmet-hooks and at least three line feeders.  Attach more as desired.

To be feasible, this requires very light but strong line of some kind.  The
line feeders must draw in slack very quickly, and measure accurately.  Still,
the mechanism should be less cumbersome than helmet-mounted cameras.

If used for both position and orientation, you need to invent a wiring plan
that allows maximum rotation of head, before the lines touch each other.  I
don't think you can get much more than 90 degrees each way.

If used for position only, use a single helmet-hook, and have unrestricted
head rotation.  Also, you have greater position range without tangling.
Perhaps use another scheme (gyros, etc.) for orientation.

Total cost is little more than the cost of the line-feeders and their
data interface.  Assuming they make such line-feeders that measure 
accurately.  Does anyone know of such a device?

Has anyone already tried this?  Anyone want to?

Hoping I've described it clearly enough,
-James

PS  Respond to me via email-- news feed can be flakey.


[MODERATOR'S NOTE:  They use a similar system at Tokyo Technical University
to measure hand position and to give a measure of feedback.  It is a cum-
bersome system that was abandoned awhile back. -- Bob Jacobson]