Computer Compositing

[T3D Michael Gordon <mgordon@xxxxxxxxx>]

>With today's tools you could put those images
>into your computer and *fix* the parallax problem in the images themselves
>then reconvert to film. This would be a much more ideal solution if the
>problem is severe enough and worth being fixed. 

Have you actually tried it?  The image is scanned into a perfectly planar
bitmap and "objects" as such do not exist.  With a great deal of effort you
can mask outline an object and cut it to its own layer, but then you must
re-create what was hiding behind the object, sometimes you can borrow
(clone) from the other image.  That works, though is extremely painstaking,
for flat objects; but an object viewed obliquely already has a continuously
varying parallax change, which you decide to alter subtly!  Good luck!

If you START with a computer generated image, where every object is either
coded on a layer, or as an object, or exists in virtual space (ie,
raytracing), then it is easy to adjust the various parameters of parallax
and perspective.

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.

Similarly, he supposed that with a computer, all one need do is click on the
apple in the photograph and move it so its perspective would not be so
great, for example.  But the computer does not "see" the apple, though if it
is strongly marked against the background you can automatically wrap a
selector mask around it, and move it -- but that exposes white underneath!
Yes, it can be done, but it is really difficult.

Sincerely,
Michael Gordon


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