(to appear SIGGRAPH 2013)
In fluid simulation, enforcing incompressibility is crucial for realism; it is also computationally expensive. Recent work has improved efficiency, but still requires time-steps that are impractical for real-time applications. In this work we present an iterative density solver integrated into the Position Based Dynamics framework (PBD). By formulating and solving a set of positional constraints that enforce constant density, our method allows similar incompressibility and convergence to modern smoothed particle hydrodynamic (SPH) solvers, but inherits the stability of the geometric, position based dynamics method, allowing large time steps suitable for real-time applications. We incorporate an artificial pressure term that improves particle distribution, creates surface tension, and lowers the neighborhood requirements of traditional SPH. Finally, we address the issue of energy loss by applying vorticity confinement as a velocity post process.
The authors would like to thank NVIDIA for supporting our research, especially Nuttapong Chentanez, Tae-Yong Kim and Simon Schirm for their valuable feedback, Simon Green for his rendering work, and Adam Moravanszky and Christian Sigg for their encouragement. We also wish to thank the anonymous reviewers for their generous comments and suggestions. The Bunny and Armadillo models are used courtesy of the Stanford Computer Graphics Laboratory.