P3D Cyclopean vision

[abram klooswyk <abram.klooswyk@xxxxxx>]

I will need more time to read Bruce Springsteen's series on
Nomenclature and Larry Berlin's reactions. However, first a quick
note on the Cyclopean image issue.

Larry wrote (P3d 3649, 15 Dec 1999):
>I will point out it's a significant mis-use in light of current
>knowledge.
>*Cyclopean* CANNOT accurately apply to the inner mental experience
>of stereoscopic vision as a Cyclops has only one eye, and would see
>the world strictly in 2D.
(...)
>The synthesis of two images into one fully structured 3D and
centralized
>comprehension is inherent ONLY to two eyed creatures. It is completely
>an ERROR to apply the term Cyclopean to this unquestionably binocular
>function.

I'm afraid Larry misses the point by ignoring the history of research
in binocular vision.
It has wondered several scientists in many centuries that we have
two eyes, but see one single world. Many solutions have been proposed,
including the idea that always one image is suppressed, and Descartes'
idea that some little man in the brain is doing the coordination.

When you compare the visual directions from one eye with the
visual directions you have with both eyes combined, in the latter
case it seems that different directions meet in a point midway
between the eyes, and a little behind the forehead.
Forerunners of this idea go back to Alhazen in the 11th century,
but the geometrical definition of binocular visual direction and
the term "cyclopean" date from the 19th century (Hering and
von Helmholtz).
So the cyclopean eye was at first a purely geometrical concept,
which had nothing to do with stereoscopic vision. The choice of the
term is clear, as geometrically there seems to be a single eye
midway the anatomical ones. (The Cyclops was the one-eyed giant in
Homers' Odyssea which liked men for breakfast, but was blinded by
Odysseus and his companions. The cyclops-myth no doubt is based on
a fortunately rare malformation, sometimes cyclops-babies are born.)

In 1971 Bela Julesz wrote his hallmark book "Foundations of
Cyclopean Perception", in which he summarized research with
computer generated random-dot stereograms.
Before Julesz one of the ideas on binocular perception was that
the images formed in each eye were analysed (for example with
Gestalt techniques) and that subsequently the extracted forms
were combined in the brain to a single unified percept.

Julesz however showed that two images, which don't reveal any form or
shape in either picture, can be combined in the brain to a 3D-form.
He used the analogy of a "cyclopean retina", which is used to
see these forms.
An interesting detail is that mathematical formulae which
describe for example a torus, can be fed to the computer to
produce a random-dot stereopair, and that in viewing the brain
(with its "cyclopean retina") sees the form. This stereo picture
is not an _image of_ an existing object, the left nor the right
hand picture show a form, the object only exists as an illusion,
for as long as you look.

So Julesz' usage is a generalization of the concept "cyclopean" to
include stereo vision.
Larry is right of course that a cyclops would have no stereo
vision, but the term has a history, is fully accepted in
vision research, and I believe everyone is aware that it is
only an analogy.

Abram Klooswyk