Interactive Physically-Based Control of Skeleton-Driven Deformable Characters

Abstract

We present an intuitive way to create dynamic motions for physically simulated, skeleton-driven deformable characters. The motion of the character is guided by the user interactively through Cartesian space control and a combination of setpoint selection. To make direct manipulation of a physically simulated character intuitive, we present a novel approach to Cartesian space control, in which the user may directly drive the accelerations or velocities of bones in the character using mouse drags and scripted constraints. To facilitate direct user control, we must solve the fully nonlinear equations of motion at speeds close to real-time. To achieve this fast computation speed, we model the deformable body as a coarse mesh having an embedded fine surface and apply a geometric recursive dynamics algorithm for fast computation and analytic differentiation. These techniques are not sufficient for good performance, however. We present an improved diagonalization method to efficiently handle mesh elements with large deformation and a number of other optimizations that allow us to achieve simulation speeds that approach real-time.