Optimization for Sag-Free Simulations

Abstract

A common problem during the first few seconds of a cloth, hair, or flesh simulation is that the mesh sags under gravity, which can undo the work of hours of careful modeling. The typical response of increasing the stiffness of the mesh is unsatisfactory as it increases the computational cost of simulation and adversely impacts the quality of the resulting motion. Modelers are accustomed to creating geometry as it is found in the real world, whichalready includes the effect of gravity. We propose a fast and effective approach for optimizing parameters such as spring rest lengths so that the artistically modeled shape represents the equilibrium after the mesh has settled under gravity. This eliminates sagging, preserves the quality of motion, and is intuitive for the artists.