P3D "impossible" images in stereo

[John W Roberts <roberts@xxxxxxxxxxxxxxxxx>]

With all of this discussion of the impossibility of making convincing
"impossible" images in stereo, a potentially important issue is being
left out: stereo imagery isn't *really* 3D. Conventional stereo provides
two images (compared to 2D, which provides one image), and "real" 3D
provides an infinite number of images. There are shapes for which stereo
cannot convey a realistic impression of the true 3D shape.

The 2D "impossible images" take advantages of the fact that there's only
one view, in order to fool the human perceptual system in an interesting
way. So - can anyone think of stereo (2-view) images that take advantage
of the fact that there are only two views, to fool the human perceptual
system in interesting ways?

Please note two items:
 - The discussion has mainly been around Escher images, but I think the
   general case would also be worth exploring.
 - It is key to the concept that the ways in which the visual system is
   fooled be "interesting". A photograph of an opaque cube with a smiley
   face painted on the side of the cube facing away from the camera is
   an "illusion" because a person who views the photograph can't see the
   smiley face, but it's not a particularly interesting illusion. :-)

John R