Constrained Animation of Flocks
Group behaviors are widely used in animation, yet
it is difficult to impose hard constraints on their behavior. We describe a new
technique for the generation of constrained group animations that improves on
existing approaches in two ways: the agents in our simulations meet exact
constraints at specific times, and our simulations retain the global properties
present in unconstrained motion. Users can position constraints on agents'
positions at any time in the animation, or constrain the entire group to meet
center of mass or shape constraints. Animations are generated in a two stage
process. The first step finds an initial set of trajectories that
exactly meet the constraints, but which may violate the behavior rules. The
second stage samples new animations that maintain the constraints while
improving the motion with respect to the underlying behavioral model. We
present a range of animations created with our system.