Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!cs.utexas.edu!rutgers!cmcl2!lanl!opus!mlandis
From: mlandis@nmsu.edu (Marvin Landis)
Newsgroups: comp.sys.amiga
Subject: re: sa4d
Keywords: Sculpt Animate keyframe animation
Message-ID: <334@opus.NMSU.EDU>
Date: 26 Sep 89 16:49:12 GMT
Reply-To: mlandis@opus.UUCP (Marvin Landis)
Organization: New Mexico State University
Lines: 39

After my last posting on this subject, I realized I made a small mistake
in my diagram if you want to do squash and stretch.  Then Stan Fisher
pointed out that "steps" would occur in the animation using my method, so
I thought I would post a second message and clear a few things up.
(And anyway I wasn't listed on the latest Bandwidth Waster's Hall of Fame
and I felt really left out :-)

First, I should have stressed the use of squash and stretch more in my
original posting.  Yes, there would be steps in the speed of the ball using
the keyframes as I described, however if the ball is stretched in each
keyframe as it falls, I feel the illusion created is good
enough you cannot detect this "stepping".  I admit it is still
not an exact imitation of a falling ball, but its easy and I have done 
a bouncing ball animation using this method its practically impossible to
see the stepping in speed.

So here's the new diagram, with one new keyframe necessary for squash and
stretch:

o  Keyframe 1
o  Keyframe 5  (still no stretch)

o  Keyframe 9  (stretch the ball a small amount)


o  Keyframe 13  (stretched some more)



O  Keyframe 17  (stretched to its maximum)     This is the frame I forgot.
o  Keyframe 18  (squashed as it hits the groud)
----------

Try it, I think you'll find that since the ball changes shape each 
frame, this helps cover the stepping speeds problem.  After all
its easy, and its all an illusion anyway :-)

Marvin Landis
mlandis@nmsu.edu