Re: 3-D phenomenon

[P3D Jim Crowell <crowell@xxxxxxxxxxxxxxxxx>]

At 12:59 PM 6/7/96, P3D Gregory J. Wageman wrote:
>
>>What I was saying is that there are many ways to get the 'depth' information
>>and 'out of focus' should not be discarded as just 'noise.'  If you
>>provide a means for your brain to interpret the focus information, it
>>is possible to percieve that 'depth' thing which is the 'illusion' of
>>3-D.
>
>All of reality is "in-focus" all of the
>time; it is our *vision system* that is selectively focusing, and yes,
>that does give us a depth cue.  But we do exactly the same thing when we
>view a Realist slide *if* it contains both near (in front of the window)
>and far subjects (behind the window).

Actually, that's not quite right; when you look at objects at
different distances in a stereo view, the convergence angle of
your eyes changes but the focal length of your eyes' lenses
(your accomodation) doesn't.  It's generally believed that
aoccomodation is only useful as a depth cue out to about 2
meters, though, & even there it's pretty weak.

Besides sensing your eyes' accomodative state, you could also
calculate depth from the way in which objects at different
depths blur as you change focal length.  I just got back from a
conference at Wright-Patterson Air Force Base where ome guys
from UT Austin reported having done just that; they have an
algorithm that'll calculate a depth map from a number of
photographs of a scene taken with a single lens at different
focus settings.  The same group has also developed a foveated
imaging sytem that will track your eyes & only present fine
detail in the portion of the image you're actually looking at
(so for example, if you were remotely controlling a vehicle
you'd only need about 5% of the image transmission bandwidth.
Quite nifty.

I'd agree, though, that the loss of this very weak depth
information is much less important than being able to scan the
scene & have everything be sharp.

-Jim C.


------------------------------------------------
Jim Crowell
School of Optometry
360 Minor Hall
University of California
Berkeley, CA 94720-2020
(510) 642-7679
jim@xxxxxxxxxxxxxxxxx
http://john.berkeley.edu/IndividualPages/jim.html



------------------------------