Re: Computer Compositing

[T3D john bercovitz <bercov@xxxxxxxxxxx>]

>> One friend of mine, B.D., who has been making stereo photographs since
>> before I was born, supposed that all one needed to do to turn a flattie into
>> stereo, would be to scan a photograph, rotate it a degree or two, scan it
>> again and rotate it the other way a degree or two.  I explained that the
>> result would look like a perfectly flat photograph that had been curled
>> around a vertical axis.  Each eye would see exactly the same information,
>> however, a distortion field would be present that would cause curvature of
>> the plane.

> Your friend was on the right track except that you have to
> do that turning process for each part of the image independently. AND you're
> right, except it would be a flat (not curled, but maybe this is what you
> meant...) reproduction plane not perpendicular to the viewer. The basic fact
> is that you are supposed to see the same image elements with each eye. If
> you don't you encounter retinal rivalry. Parallax is only small amounts of
> horizontal displacement. Depth is all relative to the repetition spacing of
> each picture element. Compression or expansion in a horizontal direction
> accomplishes the needed parallax for any given small area. (NOT a one-step
> direct solution for excess parallax overall.)

You're actually talking about two different things here.  Larry is talking 
about shifting an image part which results in a flat image and Michael was 
talking about taking slanty views of the image part, one from the right and 
one from the left, which results in keystoning in each view and that causes
curved hyberbolic distortion of a flat surface.

John B


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End of TECH3D Digest 37
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