stereovision question

[P3D <gosfield@xxxxxxxxxxxxxxxxx>]

i got out a buncha my textbooks to remind myself of the physiology and 
neurology of stereopsis, to write up a summary for photo-3d, but it's 
just too darn much to summarize at any length people could tolerate.

However: check out Principles of Neural Science, Second Edition, E.R. 
Kandel, and J.H.Schwartz eds. (THE standard neuro text in med schools) 
Elsevier, New York, 1985.  There is a newer edition, so this one may even 
be around in used bookstores cheap, and will certainly be at any good 
library.  Check pp872-874 for a limited but very clear discussion of the 
basics of stereopsis.  There is a whole section on the neurology of 
vision, but it takes about a week to digest.

Also--during my casting about for easy/accessible explanations, i did a 
Medline search of all listed articles with the keyword 'stereopsis' in 
the last 2 years, and ended up looking through ~160 abstracts.  I 
downloaded the most interesting ones (including one which asserts that 
most "educated adults"  have lost depth perception "in everyday life"!) 
and if there is sufficient interest i would be happy to post the 
references with access info.  On the other hand, i was one of those 
complaining about excessively long posts (of binary materal) so i am not 
about to put it up here unless folks really want it.  

I don't think i can email the thing to multiple respondents, but maybe 
there is some other way to handle it Bob?

>From Kandel:

"although perceptionof spatial depth is possible with purely monocular 
cues, such as motion parallax, perspective, texture gradients, and size, 
binocular vision creates a totally new visual dimension--_stereopsis_.  
Stereopsis allows us to perceive a three-dimensional object in spatial 
depth, an aspect of perception that would be possible wth monocular vision"

" For a given fixation point, there is a locus of points called the 
_horopter_, along which images fall on corresponding points of the two 
retinas."

"For points along the horopter, the area of temporal retina stimuylated 
by light in one eye corresponds to a nasal area in the other eye."

in the optic chiasm there is a "decussation [crossing over] of the optic 
nerve fibers from each eye in order to anatomically associate 
corresponding areas of visual space in the brain"

Visual information is also shared between the hemispheres through the corpus 
callosum.

experiments with random dot stereograms (which have depth clues due to 
parallax, but no monocular info about the shape of the object) show that 
the process of stereopsis  precedes the stage at which the object shape 
is recognized.

....all the above quoted or paraphrased from the citation..i had better 
stop before i violate copyright.  It's a VERY complex subject.  

ted gosfield
gosfield@xxxxxxxxxxxxxxxxx



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