From: J.P.Wann@RDG.AC.UK
Subject: Re: TECH: Driving Simulators - Curved Paths
Date:         Tue, 4 Jun 1996 11:50:25 +0100


>Hendrik-Jan van Veen (veen@newsserv.zdv.uni-tuebingen.de) wrote:
>: Did anyone ever try one of these alternative ways of simulating
>: changing direction of movement or did anyone ever think about this
>
> and Oren Levine (ohl@world.std.com) replied:
> One way of solving this problem is to tie the viewing direction of
> the simulator to the viewing direction of the user's head....If the
> display device is an HMD...or...For other simulators, you'll have to
> find a way to track the direction in which the user is looking
>

This is a more complex problem than it seems at first: If you are
driving around a curved path your motion can be decomposed into a
forward translation + rotation. Similar retinal motion patterns
however result from pure forward translation (a straight line
trajectory) + a gaze rotation.  The bottom line is if you had a
similator that was head responsive in this manner, then someone who
was sat BEHIND the driver wouldn't be able to tell from the display
whether they were on a curved path, or a straight path with driver
gaze motion superimposed.

The flaw in using Hendrik's suggestion is that you would be
introducing optical rotation at the rendering stage that may not
precisely reflect the gaze motion (e.g. due to small tranduction
errors or transmission lags) and unless the actual and rendered gaze
motions matched perfectly, then the driver would mis-perceive their
heading.  In the standard (static viewpoint) simulator display, gaze
rotations are only introduced into the retinal flow if the eye
actually moves, hence they are always veridical.

This is a difficult topic to get your head round, but
gaze-heading-steering is an area we have ongoing research in, so if
anyone wants more info then contact us directly.

John W.

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Dr John P. Wann  <john1@ed.ac.uk>  or < J.P.Wann@rdg.ac.uk>
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