Dynamic free-form deformations for animation synthesis

Free form deformations (FFDs) are a popular tool for modeling and keyframe animation. The paper extends the use of FFDs to a dynamic setting. Our goal is to enable normally inanimate graphics objects, such as teapots and tables, to become animated, and learn to move about in a charming, cartoon like manner. To achieve this goal, we implement a system that can transform a wide class of objects into dynamic characters. Our formulation is based on parameterized hierarchical FFDs augmented with Lagrangian dynamics, and provides an efficient way to animate and control the simulated characters. Objects are assigned mass distributions and elastic deformation properties, which allow them to translate, rotate, and deform according to internal and external forces. In addition, we implement an automated optimization process that searches for suitable control strategies. The primary contributions of the work are threefold. First, we formulate a dynamic generalization of conventional, geometric FFDs. The formulation employs deformation modes which are tailored by the user and are expressed in terms of FFDs. Second, the formulation accommodates a hierarchy of dynamic FFDs that can be used to model local as well as global deformations. Third, the deformation modes can be active, thereby producing locomotion.