Title: Physically-Based Combinations of Views: Representing Rigid and Nonrigid Motion
Author: S. Sclaroff and A. P. Pentland
Date: November, 1994

Abstract:

Nonrigid motion can be described as morphing or blending between
extremal shapes, e.g., heart motion can be described as transitioning
between the systole and diastole states.  Using physically-based
modeling techniques, shape similarity can be measured in terms of
forces and strain.  This provides a physically-based coordinate system
in which motion is characterized in terms of physical similarity to a
set of extremal shapes.  Having such a low-dimensional
characterization of nonrigid motion allows for the recognition and the
comparison of different types of nonrigid motion.