Articulated Motion and Deformable Objects

This paper presents Virtual Clay as a novel, interactive, dynamic, haptics-based deformable solid of arbitrary topology. Our Virtual Clay methodology is a unique, powerful visual modeling paradigm which is founded upon the integration of (1) deformable models, (2) free-form, spline-based solids, (3) procedural subdivision solids of arbitrary topology, and (4) dynamic objects governed by physical laws. Solid geometry exhibits much greater modeling potential and superior advantages to popular surface-based techniques in visual computing. This is primarily because a CAD-based solid representation of a real-world physical object is both geometrically accurate and topologically unambiguous. We first introduce the concept of Virtual Clay based on dynamic subdivision solids. Then, we formulate the mathematics of Virtual Clay through the integration of the geometry of subdivision solids with the principle of physics-based CAGD. Our Virtual Clay models respond to applied forces in a natural and predictive manner and offer the user the illusion of manipulating semi-elastic clay in the real world. We showcase example sculptures created with our Virtual Clay sculpting environment, which is equipped with a large variety of real-time, intuitive sculpting toolkits. The versatility of our Virtual Clay techniques allows users to modify the topology of sculpted objects easily, while the inherent physical properties are exploited to provide a natural interface for direct, force-based deformation. More importantly, our sculpting system supports natural haptic interaction to provide the user with a realistic sculpting experience. It is our hope that our Virtual Clay graphics system can become a powerful tool in graphics, computer vision, animation, computer art, interactive techniques, and virtual environments.