Abstract: In this paper, we present a technique for motion: the problem of adapting an animated motion from one character to another. Our focus is on adapting the motion of one articulated figure to another figure with identical structure but different segment lengths, although we use this as a step when considering less similar characters. Our method creates adaptations that preserve desirable qualities of the original motion. We identify specific features of the motion as constraints that must be maintained. A spacetime constraints solver computes an adapted motion that re-establishes these constraints while preserving the frequency characteristics of the original signal. We demonstrate our approach on motion capture data.