We propose a simple framework for making elastic body animation with point constraints. In general, a physics-based approach for constraint animation offers a variety of animations with physically correct realism, which are achieved by solving the equations of motion. However, in the digital animation industry, solving the equations of motion is an indirect path to creating more art-directed animations that maintain a plausible realism. Our algorithms provide animators a practical way to make elastic body animation with plausible realism, while effectively using point-constraints to offer directatorial control. The animation examples illustrate that our framework creates a wide variety of point-constraint animations of elastic objects with greater directability than existing methods.

　　
[ A (left)] Initial animation. Point-to-point constraints are applied between the characters and the bench. One of the constraints between the fish and the bench is turned off near the end of the animation (the bottom of [A]).
[ B (middle)] Directing the duck by making keyframes so that the duck is pulling and throwing the fishes.
[ C (right)] Final animation. The user modifies the trajectory so that the fish can reach the big duck. At the instant of collision, a new point-to-point constraint is added, so the fish sticks to the big duck.



[Publication]
Ryo Kondo, Ken Anjyo,"Directable Animation of Elastic Bodies with Point-Constraints", In The Journal of Computer Animation and Virtual World (CASA 2008, Volume 19, Issue 3-4, pp.165-173, Seoul, Korea, Sept. 1-3 2008)