Anurag.Acharya@CENTRO.SOAR.CS.CMU.EDU (02/29/88)
TOPIC: Physically Based Modeling For Vision And Animation SPEAKER: Andy Witkin, Purdue University WHEN: Thursday, March 3, 1988, 3:30-4:30 p.m. WHERE: Wean Hall 5409 ABSTRACT Our approach to modeling for vision and graphics uses the machinery of physics. We will describe two current foci of our research: To create models of real-world objects we use simulated materials that move and deform in response to applied forces. Constraints are imposed on these active models by applying forces that coerce them into states that satsify the constraints. In visual analysis, the constraint forces are derived from images. Additionally, the user may apply forces interactively, guiding the models towards the desired solution. Examples of the approach include simulated pieces of springy wire attracted to edges, and symmetry-seeking elastic bodies used to recover three-dimension shapes from 2-D views. To animate active character models we use a new method called ``spacetime constraints.'' The animator specifies what the character has to do, for instance, ``jump from here to there, clearing a hurdle in between;'' how the motion should be performed, for instance ``don't waste energy,'' or ``come down hard enough to splatter whatever you land on;'' the character's physical structure---the geometry, mass, connectivity, etc. of the parts; and the physical resources available to the character to accomplish the motion, for instance the character's muscles, a floor to push off from, etc. The requirements contained in this description, together with Newton's laws, comprise a problem of constrained optimization. The solution to this problem is a physically valid motion satisfying the ``what'' constraints and optimizing the ``how'' criteria. We will present animation of a Luxo lamp performing a variety of coordinated motions. These realistic motions conform to such principles of traditional animation as anticipation, squash-and-stretch, follow-through, and timing. We will conclude with a videotape presenting an overview of our recent vision and animation work. -----------------------------------------------------------------------