Fitting solid meshes to animated surfaces using linear elasticity

Computing correspondence between time frames of a time-dependent 3D surface is essential for the understanding of its motion and deformation. In particular, it can be a useful tool in compression, editing, texturing, or analysis of the physical or structural properties of deforming objects. However, correspondence information is not trivial to obtain for experimentally acquired 3D animations, such as time-dependent visual hulls (typically represented as either a binary occupancy grid or as a sequence of meshes of varying connectivity). In this article we present a new nonrigid fitting method that can compute such correspondence information for objects that do not undergo large volume or topological changes, such as living creatures. Experimental results show that it is robust enough to handle visual hull data, allowing to convert it into a constant connectivity mesh with vertices moving in time. Our procedure first creates a rest-state mesh from one of the input frames. This rest-state mesh is then fitted to the consecutive frames. We do this by iteratively displacing its vertices so that a combination of surface distance and elastic potential energy is minimized. A novel rotation compensation method enables us to obtain high-quality results with linear elasticity, even in presence of significant bending.