Subject: Multiple-target morphing
From: [email-masked] (Kevin Bjorke)
To: [email-masked]
Date: Tue, 7 Feb 95 13:33 PST

Nostradamus predicted that Sean would write:

> It would be great if LW incorporated a technique more like "displacements"
> where multiple object targets may be mixed freely.  I believe the technique
> was developed by Matt Elson on Symbolics equipment.         

Matt showed up late in the game, this technique was being used in REAL TIME
at least as early as 1986, and I believe that it is also the mechanism
used to recreate muscle groupings in Fred Parke's old facial-animation papers
of the 1970's. It is, however, particularly effective in a programmable-
modeling animation system like the Symbolics. 

To further generalize the technique, one can remember that the displacements
are really a vector set applied to the model vertices -- each a direction
and a magnitude. If we allow the magnitudes to be program-controlled, say
by using relaxation between nodes or by varying their strengths based on
distance traveled of spline functions, then even more-organic-looking movements
can be made. Also, the target directions can be uniformly or randomly
rotated, scaled, etc. Imagine a chewing cow.

Another enhancement is to allow the path of action between the origin and
destination points be non-linear -- great for, say, pouting lips or eyelids,
which ROTATE to their destinations. This last enhancement WAS used by Matt
Elson, at least by the time of the "Virtually Yours" short.  It can be seen
in the wrist rotations, as an example.

All this puts a tremendous burden on the modeller -- these techniques have
been known in the industry for some time, but they are very manpower-intensive
(read: expensive).

---- Kevin Bjorke ---- Animation Scientist ---- Hi Tech Toons ----
            -------  Nana - korobi  ya - oki  --------