Re: Headtracking with the screen (not HMD) as projection plane

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David A. Southard (southard++at++draper.com)
Wed, 16 Oct 1996 12:18:35 -0400 (EDT)

The off-axis method should be best. One issue to consider is whether the
offsets between the tracker sensor and your actual eye position, and
between the tracker receiver and the screen, are taken into consideration.
If all the offsets are accounted for, then the objects should not be
distorted nor will they appear to move as you move your head. They should
appear stationary in space, except for any tracking/update delay.

Check out my article on this subject:

D. A. Southard, Viewing model for virtual environment displays, Journal of
Electronic Imaging 4(4) 413-420 (October 1995).

It gives algorithms for HMDs or head tracking based on matrix
transformations, which are compatible with Performer, and measurements that
you take from your display setup.

If you end up using it please let me know your results and comments.

>This is not a Performer question, but perhaps someone can give me a hint:
>
>What is the best projection for headtracking (with a ultrasonic or magnetic
>tracker) with the workstation or other screen as projection plane?
>
>I tried two ways:
>
>1. Way
>
>Off axis projection (asymmetric frustum) with the frustum defined by a near
>plane parallel to the screen:
>
>
> .------------------------------. far
> . .
> . .
> ---------------------- screen
> . .
> . .
> . l r . l...left
> .------|---. near r...right
> . | .
> . | .
> .|.
> eye = tracker position
>
>
>The problem is, that objects are distorted.
>
>2. Way:
>
>With an on axis projection (symmetric frustum) the objects look ok but if you
>move the head, it looks as they are moving.
>
>
>Thanks for any answers
>Regards
>Daniela
>
>--
>-------------------------------------------------------------------------
>Daniela Rainer | email: rainer++at++rus.uni-stuttgart.de
>Rechenzentrum Uni Stuttgart (RUS) | Tel: +49 (0) 711 685 5970
>Allmandring 30a, 70550 Stuttgart | Fax: +49 (0) 711 678 7672
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Dr. David A Southard mailto:southard++at++draper.com
Charles Stark Draper Laboratory MS-3F tel:617-258-4276
555 Technology Square fax:617-258-2555
Cambridge MA 02139-3563

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