One eyed 3D

[P3D Peter Homer <P.J.Homer@xxxxxxxxxxxxxxxxx>]

One example of a 3D illusion of stereo at least was the "Rotoreliefs" of
the serealist artist Marcel Duchamp . These consisted of sightly of
centered spiral patterns which when rotated gave the illusion of a
precessing cone sticking out in space when viewed with one eye. They were
marketed for a while for use on record turntables but have turned up since,
in adverts in american superman comics etc in the 60.s with the claim that
they could hypnotise people. I have a record from the 70,s Black Sabbaths
Master of Reality which has such a pattern for its label on one side.
Actualy at that time I think that was the Vertigo record label logo and
they all had it . Only recently have I noticed the effect of viewing it
with one eye after reading about Duchamp. He even produced actual three
dimensional versions of them by drawing the spirals on domes and filmed
them rotating stereoscopicaly for anaglyph projection . I have seen a side
by side stereo pair taken from this film in an art book but have not been
able to track it down since. Apparently his thinking behind doing this was
that if a single eye could produce the third dimension a two eyed version
should produce further dimensions!. I suppose the fourth of time was
present because there was movement but that would apply equaly to the
single eye version . What I think happens here is that with shapes like
this the mirror image is the opposite eye view . Wheatstone himself
experimented with this using a mirror to provide the other view , rotating
these devices presents the left end right views in alternation and the
brain seems to retain the one image long enought to combine it with the
other. Closing one eye probably helps by preventing normal stereo vision
from contradicting the illusion . This may explain the  method just
mentioned on the list and also some time ago of alternating smoothly
between the pairs on a video to be viewed without glasses and maybe it is
also partly responsible for the Pulfrich effect .
                                               P.J.Homer



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