P3D Re: "Hollow Face" illusion

["wier@xxxxxxxxxxxxxxxxx"<wier@xxxxxxxxxxxxxxxxx>]

>I bought an interesting item from Edmund Scientific.  It is called "The
>Living Image" and it is essentially a hollow mask (the inside of a mask)
>mounted on a display with a fluorescent tube lighting it underneath.  This
>display has some interesting properties, of interest to stereo vision.
>
>Viewed at a distance the depth appears reversed, i.e., instead of the
>hollow (back) end, one normally sees the front of the mask, a face, looking
>at them.  The illusion is so strong that most people have to come very
>close or even touch the mask to get back the correct hollow image.

Yes - there is a quite strong similar illusion involving a series
of cube "hollows" which appear to be solid. I saw one once at the
Exploratorium in SF. One particularly interesting thing is that
as you move your head back and forth, the cubes seem to have a 
counter movement in the WRONG direction. Very unsettling.

--BW

              Bob Wier
     mailto:wier@xxxxxxxxxxxxxxxxx
   9:37 AM Thursday, September 30, 1999
        Unix/Internet Administrator
   Rocky Mountain College, Billings MT.
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