Interactive Manipulation of Rigid Body Simulations

Physical simulation of dynamic objects has become commonplace in computer graphics because it produces highly realistic anima- tions. In this paradigm the animator provides few physical param- eters such as the objects’ initial positions and velocities, and the simulator automatically generates realistic motions. The resulting motion, however, is difficult to control because even a small adjust- ment of the input parameters can drastically affect the subsequent motion. Furthermore, the animator often wishes to change the end- result of the motion instead of the initial physical parameters. We describe a novel interactive technique for intuitive manipula- tion of rigid multi-body simulations. Using our system, the anima- tor can select bodies at any time and simply drag them to desired locations. In response, the system computes the required physical parameters and simulates the resulting motion. Surface characteris- tics such as normals and elasticity coefficients can also be automat- ically adjusted to provide a greater range of feasible motions, if the animator so desires. Because the entire simulation editing process runs at interactive speeds, the animator can rapidly design complex physical animations that would be difficult to achieve with existing rigid body simulators.