ScrewBender : Polyscrew Subdivision for Smoothing Interpolating Motions

An ordered series of control poses may be interpolated by a polyscrew rigid body motion composed of a series of screws, each interpolating a pair of consecutive control poses. The trajectory of each point during screw motion is (C∞). Although a polyscrew is continuous, velocities are typically discontinuous at control poses when the motion switches between screws. We obtain a smooth motion by subdividing the polyscrew. Three subdivision schemes are proposed: the interpolating 4-point subdivision, the smooth cubic B-spline subdivision, and the Jarek subdivision, an average of these two. Their implementation is trivial and their computation sufficiently fast for realtime subdivision and animation, which is particularly important for interactive motion editing and hardware support for animation.