siggraph@pioneer.arpa (Siggraph) (04/20/88)
The next meeting of the Bay Area Association for Computing Machinery Special Interest Group on Computer Graphics (ACM/SIGGRAPH) Physically Based Modeling For Vision And Animation Andrew Witkin Michael Kass Demetri Terzopoulos Kurt Fleischer Schlumberger Palo Alto Research The speakers are researchers at Schlumberger Palo Alto Research, and the producers of critically acclaimed short videos, including "Knot Reel" and "Cooking with Kurt." They have published a number of papers in recent ACM/SIGGRAPH Proceedings, as well as elsewhere. Computer animators, and would-be animators, should make themselves aware of the exciting potential of these ground breaking methods. Here's how our speakers describe their work: 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. Elasticity theory is used to construct nonrigid curves, surfaces, and solids that model the behavior of elastic materials such as rubber, and inelastic materials such as clay or silly putty. These deformable models respond actively to applied forces and impenetrable obstacles in a simulated physical environment. Forces are also used to coerce the models into states that satisfy constraints. Realistic animation is produced by solving the differential equations of motion numerically. In visual analysis, we employ constraint forces, derived from images, to create models that mimic the shape and motion of objects observed in 2-D images. Examples of this approach to vision include simulated pieces of springy wire attracted to edges, and symmetry-seeking elastic bodies used to recover three-dimensional shapes from 2-D views. To animate active character models we use a new method called ``space-time 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. Date: Tuesday, April 26 Time: 8:00 PM Place: Xerox Palo Alto Research Center (PARC) 3333 Coyote Hill Road, Palo Alto