P3D Re: What is Hyperstereo?

[Bruce Springsteen <bsspringsteen@xxxxxxxxx>]

Dan Shelley answered this one well.  Hyperstereo is shooting with a lens
separation larger than the average human interpupillary distance - about
2.5" or 64 mm.

To anticipate the next question, hypostereo is shooting with less than
that average distance. 

Dan says hyperstereo is helpful to "amplify" the stereo information in an
image.  This is a hard notion to get intuitively, and is often confused
with "stretching" the apparent depth of objects in a scene.  The problem
we are trying to solve is: objects that are not near to you don't reveal
much of their form in stereo, less so the farther from you they are. 
Increasing the stereo base reduces the apparent size and distance of
objects in a scene, so they appear to be in that nearby range where stereo
perception is most acute.  Let me try a poor analogy I call "Hugging the
Elephant".

If an elephant was standing in front of you, about 10 feet away, and you
wanted to get some idea of its shape by touch, without opening your eyes
or moving about, you would reach forward with both arms and try to wrap
them around the beast.  But your arms are only so long and so far apart,
and couldn't feel far enough around him to detect much more that his
"flat" side, if you reached him at all.  The relative shapes and position
of his torso, legs, ears and trunk would be beyond the scope of your
perceptual apparatus (arms).

But if you grew to a height of maybe 30 feet, about 5 times your current
scale, your ability to reach to and around the elephant would greatly
improve.  From your relative perspective, he would seem one 1/5 as far and
1/5 as large as before, and you could easily get a "feel" for his shape,
which would seem smaller and nearer but undistorted.

If a distant object is too far and large to "wrap" your eyes around it and
stereoscopically discern its shape, enlarging the stereobase makes it
appear smaller and closer, by making you "bigger", so you can gather the
information you need.

That explanation will probably make the serious scholars howl!

Bruce





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