P3D Re: Escher, stereo, impossibility

[abram klooswyk <abram.klooswyk@xxxxxx>]

Bruce Springsteen, P3d 3769, 6 Mar 2000: 
>(...) in the case of "impossible" images like "Belvedere", 
>"Waterfall", "Convex and Concave" and others where the 
>uncertainty of depth relationships is the whole idea (...) 

Greg Wageman, P3d 3772, 7 Mar 2000: 
>(...) Every one of these that I can think of and that has 
>been mentioned (the impossible fork, etc.) uses the same 
>'trick'.  The image is locally consistent, but not globally 
>consistent. 

Impossible figures have been analysed mathematically by Zenon 
Kulpa (from Poland), articles: "Are impossible figures 
possible", Signal Processing 1983; (5) 201-220 and: "Putting 
order in the impossible", Perception 1987; 16(2) 201-214.
He also distinguishes several classes of related figures. 
"Convex and Concave" doesn't belong to the true impossible
figures, it is more related to the Necker cube and the
intaglio-type of illusions.

There are also quite a number of psycho-physiological studies 
done on the perception of impossible figures. This is all 
related to the perception of depth, but probably not all 
within the scope of Photo-3D.

Greg: >a clever person might be able to come up with a 
>pseudoscopic pair which is as pleasing and perplexing as 
>one of Escher's impossible figures. 

You can try pseudo viewing of the anaglyphs of the Escher 3D 
conversions, at Steve Berezin's site and Michael Hodsdon's 
site (see P3d 3766). Only the "Balcony" seems interesting,
but somehow reminds of the hollow face illusion. 

(BTW, I finally could change the name of the subdirectory 
"mhgug-Mike" of my directory "3Dpeople" to "Hodsdon-Michael".
Thanks, Michael, and please keep your work on line.)

Abram Klooswyk