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5 Tips to Speed Up FLIP FLUID Simulations in Houdini 20

Let's get right into it ~

1. Substeps

For large-scale flip simulations, where accuracy is not a big issue, consider reducing the maximum substeps on the FLIP solver to 1 from 2.

2. Narrow Band

Consider turning on Narrow Band and increasing surface oversampling to generate more particles in sparse areas.

Note - Narrow Band should be automatically enabled when dropping a FLIP Configure Tank node. If not, go to the Advanced tab of the FLIP Solver and enable Enable Particle Narrow Band.

3. Solve Pressure with Adaptivity

When turned on, the pressure solver uses adaptive timesteps where possible to decrease simulation time. If you observe instabilities or exploding particles, do not use this option.

4. Use OpenCL to calculate Pressure and Viscosity

If using the SOP FLIP Solver, unlock the solver and navigate to the flipsolver1 node. Turn on the Use OpenCL checkbox in the solver tab of the flipsolver1 node. This setting primarily benefits high-resolution flip simulations with viscosity when run on a fast GPU.

5. Turn off Surface Collisions

For the tradeoff of having a less accurate collision calculation, turning off Surface Collide in the flip collide solver can help speed up FLIP simulations significantly.

After turning off this option, the next step would be to change the particle collision type from Particles to Move Outside Collisions in the Collision tab of the FLIP Solver.

Move Outside Collision is the default and the fastest collision handling method. This option provides the smoothest splashes but is not as accurate with fast-moving collision geometry. It is also the only method that works with volumetric collision objects.

If this is helpful at all, consider sharing or commenting below. If this gets enough traction, I will share 5 more tips to Speed up FLIP Fluid Simulations on this blog soon.

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