At its lowest level of abstraction, our work is an instance of physics-based graphics modeling. This approach involves constructing dynamic models of animated objects and computing their motions via physical simulation. Physics-based modeling implies that object motions are governed by the laws of physics, which leads to physically realistic animation. Moreover, this approach frees the animator from having to specify many low-level motion details, since motion is synthesized automatically by the physical simulation. This is evident especially when animating passive motion (i.e. motions of inanimate objects)--the animator need only supply the initial state of the object and a physical simulator automatically computes its motion by integrating the differential equations stemming from Newton's laws.
The success of physics-based modeling was demonstrated in modeling the movements of inanimate objects, such as deformable objects [Terzopoulos et al.1987, Terzopoulos and Fleischer1988, Witkin and Welch1990], chains [Barzel and Barr1988] and tree leaves [Wejchert and Haumann1991]. A substantial amount of research has also been concerned with the motion of animate objects, such as humans and animals [Armstrong and Green1985, Wilhelms1987, Badler, Barsky and Zeltzer1991, Hodgins et al.1995].
An animator requires control over physics-based models in order to produce useful animations. We can categorize physics-based control techniques into two approaches: the constraint-based approach and the motion synthesis approach.
|Xiaoyuan Tu||January 1996|