Re: SFX in 3D movies

[P3D Gregory J. Wageman <gjw@xxxxxxxxxx>]

Jim Crowell asks:

>What's "rotscoping"?

I guess that's when you get the inspector to determine how far gone the
wood in your foundation really is. :-)

"Rotoscoping", on the other hand, traditionally was when one or more
frames of motion picture film were projected on a animation stand, and
then the animator made a tracing, possibly with modifications, which
were then re-shot a frame at a time, animation style.  A lot of Ralph
Bakshi's animated films were shot with live actors, and then heavily
rotoscoped to get realistic-looking motion from his animated characters.

Nowadays, the film is scanned digitally and modifications made a frame
at a time in the computer, then output to a digital printer.  But the
effect is the same; you go in an alter individual pixels by hand.

In "Star Wars", they had two different land speeder mock-ups.  One was
on the end of a long boom, and had no wheels.  It really was suspended
above the ground.  However, it could only move in a circle, and could
only be shot from certain angles to conceal the boom, so when they
wanted to show Luke driving in a straight line, they used the other
one, which had wheels.  To make it appear to be hovering (and to remove
the shadows cast by the wheels), they rotoscoped those frames and
hand-retouched the underside of the vehicle.  In the film it appears
to have a wavering, vapor-like quality under it.  Those were the
rotoscoped frames.

The bearing on 3D is that if you're going to use this technique, you
have to ensure that the pixel manipulations have the appropriate
binocular disparity on the left and right images.  Otherwise,
features would seem to randomly change apparent depth, which could be
an interesting effect by itself in the right situation, but probably
not in all of them...

        -Greg


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