A technique for motion specification in computer animation

A technique is discussed for the interactive specification and real-time evaluation of the movements of geometrical objects with several degrees of freedom. The technique is a midway between a faithful simulation of the dynamics and kinematics of the object and completely free user control, and as such it is well suited for animated drawings, for example. The method works in two steps: first, the motion of a relevant subobject (the skeleton) is specified interactively in real time. Next, the entire object is deformed and oriented in space such as to match the form of the skeleton. Depending on the complexity of the object, this second step either takes place in real time, or as a batch process. Several forms of geometrical constraints, as well as stretching and squeezing, are supported.