P3D Re: "Hollow Face" illusion

["Dr. George A. Themelis" <DrT-3d@xxxxxxxxxxxxxxxxxxxxxxxxxxx>]

>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.

Yes, that's what the "face" does too.

In the instruction sheet it is mentioned that this optical illusion
is based on the "Reverse Masks" exhibit at the San Francisco
Exploratorium.  The item is copyrighted by "Fascinations Toys
& Gifts, Inc." and they give this email address:
image@xxxxxxxxxxxxxxxx

In the Edmund Scientific catalog it is listed as item #X81-553 and
it retails for $35.95.  The construction is rather cheap.  My wife
told me to get rid of it, after I put it for display in our 
living room... Kids enjoyed "playing" with it.  I guess I'll have to 
move it to "DrT's playroom" in the basement out of my wife's view :-)

George Themelis