Flexible multibody dynamics and adaptive finite element techniques for model synthesis and estimation *

This paper develops a general approach for the efficient modeling and animation of non-rigid multibody objects. We develop a new family of physics-based modeling primitives that can undergo free motions as well as parameterized and free-form deformations. Starting with parameterized geometric primitives and adding global geometric deformations, local finite-element deformations, mass distributions and elasticities, we create deformable models that display correct physical behaviors. In order to further enhance the accuracy of our shape representation we develop adaptive finite element techniques. Our algorithm ensures that during element subdivision the desirable finite element mesh properties of conformity, non-degeneracy and smoothness are maintained. In this way not only can we represent more accurately an object surface, but also more efficiently because new model nodes are added only when necessary in a local fashion. Furthermore, in the paper we adapt and implement efficient constraint methods for connecting physical primitives together to make articulated multibody objects. We demonstrate the computationally efficient performance of our algorithms for the synthesis and visualization of deformable models, as well as for estimating the shapes and motions of deformable objects.