Dynamic Splines with Constraints for Animation

Abstract

In this paper, we present a method for fast interpolation between animation keyframes that allows for automatic computer-generated "improvement" of the motion. Our technique is closely related to conventional animation techniques, and can be used easily in conjunction with them for fast improvements of "rough" animations or for interpolation to allow sparser keyframing. We apply our technique to construction of splines in quaternion space where we show 100-fold speed-ups over previous methods. We also discuss our experiences with animation of an articulated human-like figure. Features of the method include: (1) Development of new subdivision techniques based on the Euler-Lagrange differential equations for splines in quaternion space; (2) An intuitive and simple set of coefficients to optimize over which is different from the conventional Bspline coefficients; (3) Widespread use of unconstrained minimization as opposed to constrained optimization needed by many previous methods. This speeds up the algorithm significantly, while still maintaining keyframe constraints accurately.