Figure 1 : Two simulations with a (background-)grid resolution of 200 3 : Our method (left) is nearly indistinguishable from regular FLIP (right), but uses only one million particles instead of 24 million. Computations outside of the pressure solver are sped up by a factor of more than 6, the total computation time for 250 frames is reduced from 4.4h to 2h, and the average memory footprint is reduced by a factor of 2. Abstract The Fluid Implicit Particle method (FLIP) for liquid simulations

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... 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 naïve 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.