Re: What can you do in 2d that cannot do in 3d (Escher)

[P3D John W Roberts <roberts@xxxxxxxxxxxxxxxxx>]

>Date: Mon, 15 Sep 1997 14:14:47 -0500
>From: "P3D Dr. George A. Themelis" <fj834@xxxxxxxxxxxxxxxxxxxxx>
>Subject: Re: What can you do in 2d that cannot do in 3d (Escher)

>Ken Luker writes:

>>I believe one cannot, in principle, make a convincing 3d 
>>photograph of the Escher fixture.

>Since these are "impossible" objects (i.e. do not exist and cannot be
>constructed in real life) it is reasonable to expect that a convincing 3d
>photograph cannot be made.  However I believe that a 3d drawing or a 
>computer-generated image can be made and perhaps a real photograph 
>can be digitally "twisted" to produce the impossible object.

An intriguing notion! Since the 2D impossible drawings are essentially
a function of the perceptual ability of the human visual system, a 3D
equivalent would be something that uses the characteristics of the
stereoscopic visual system to produce something which looks plausible to
a human, but which is geometrically impossible.
A photo including a rainbow might be that sort of thing.

I recently saw some other interesting visual effects on a plane ride. I had
a window seat over a wing, and the reduced air pressure over the wing
caused distortions - at some angles of the sun this resulted in bright
bars of sunlight along the wing - at another time the effect appeared to be
a series of tiny vertical disruptions of the view along the wing. The
apparent location of these disruptions shifted enormously with a small
shift in head position, so it was impossible to view them stereoscopically.

John R


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