Accelerated viscous fluid simulation using position-based constraints

The most prevalent approach to simulating viscous fluids is based on the Navier-Stokes equations, and has extensively been adopted in computer graphics for the past two decades. When employing an explicit viscosity integration, however, time step size for numerically stable simulation is likely to be limited and necessitate an exceedingly long period of time for computation. In this paper, we present a novel particle-based method for efficiently simulating viscous fluids using position-based constraints. Our method utilizes the geometric configuration of particles for the positional constraints in the position-based dynamics, and thus can generate visually-plausible behavior of viscous fluids, while allowing for the use of much larger time steps than the ones previously adopted in the viscous fluid simulations. An associated boundary handling scheme for the position-based fluids is also proposed to properly address constraints for density and viscosity distributions on boundaries. In addition, by adjusting parameters of particles, our method can produce complicated dynamics of threads, sheets, and volumes of different viscosity values in a unified framework. Several examples demonstrate the efficiency as well as robustness and versatility of our approach.