Subject: motion capture (was Re: Lightwave and anime)
From: [email-masked] (Sean Cunningham)
To: [email-masked]
Date: Thu, 15 Sep 1994 19:01:32 -0700 (PDT)

Efficient and viable post-processing of motion-capture data is largely 
limited by your choreographer's curve-editer.  Since the capture data usually
comes in with a keyframe for every frame you must re-sample the curve in
order to get useable or editable curves.  Some packages might just blindly
throw out every nth keyframe and spline interpolate, but you're going to be
left with mush.

As much as I hate to give Softimage credit for anything, their curve editer
does a pretty darn good job of matching a bezier-spline to a raw capture
curve, tweaking the knots and tangents so that the "essense" of the captured
data is all there.  This helps get rid of some of the jitter associated with
captured data (analogous to the jittery result of 2D rotoscope animation).

Another method would be to use channel-math.  Add an offset curve to each
raw captured curve in order to modify the animation (XTRAN = XOFF + XRAW).
We've used this approach to fudge curves spit out by our 3D motion tracking
software (gleen XYZ position and rotation from a 2D image).

I'm also not a big fan of motion-capture, under most circumstances.  I hold
this technique with about as much contempt as 2D rotoscoping.  BUT, it can
be very useful and time-saving under the right circumstances.  "true to
life" movement does not always work, as any fan of Disney animation can
attest.  

On the positive side, and for you money-hungry animators out there, 
performance capture can introduce you to the wonderful world of royalty
checks!  Pupeteers fall under the jurisdiction of SAG, which means that you
could be pulling in bucks long after a project is over...everytime your
commercial or movie or whatever is shown on TV or at the movies :)  This is
something I hope will eventually happen for animators in general as I feel
we've been exploited by the suits for far too long in this industry.