Narrow Band FLIP for Liquid Simulations

Florian Ferstl1, Ryoichi Ando2, Chris Wojtan2Rüdiger Westermann1, and Nils Thuerey1
1Technische Universität München, Germany    2IST Austria

Abstract

The Fluid Implicit Particle method (FLIP) for liquid simulations uses particles to reduce numerical dissipation and provide important visual cues for events like complex splashes and small-scale features near the liquid surface. Unfortunately, FLIP simulations can be computationally expensive, because they require a dense sampling of particles to fill the entire liquid volume. Furthermore, the vast majority of these FLIP particles contribute nothing to the fluid's visual appearance, especially for larger volumes of liquid. We present a method that only uses FLIP particles within a narrow band of the liquid surface, while efficiently representing the remaining inner volume on a regular grid. We show that a naive realization of this idea introduces unstable and uncontrollable energy fluctuations, and we propose a novel coupling scheme between FLIP particles and regular grid which overcomes this problem. Our method drastically reduces the particle count and simulation times while yielding results that are nearly indistinguishable from regular FLIP simulations. Our approach is easy to integrate into any existing FLIP implementation.

Acknowledgements

This work was supported by the European Union under the ERC Advanced Grant 291372 SaferVis and the ERC Starting Grants 637014 realFlow and 638176 BigSplash.

Source Code

Our implementation is available in the open source solver Mantaflow (version >= 0.9).

Associated publications

Narrow Band FLIP for Liquid Simulations
F. Ferstl, R. Ando, C. Wojtan, R. Westermann, N.Thuerey, 
Computer Graphics Forum, 35: 225–232 (Eurographics 2016) 
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