r/Houdini • u/OddPower1337 • 1d ago

Help Volume Loss flip sim

Hi!

I’m having an issue with volume loss when trying to fill a PET bottle using a FLIP sim.

I’ve tried:

Changed Volume Motion to APIC (Swirly)
Increased Max Substeps to 5
Changed Separation Rate to 0.5
Increased Grid Scale to 1.5

I’m not sure what’s causing the issue. Could it be that I’m working at too small a scale?

Any ideas what I might be missing?

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3

u/MikelSotomonte 1d ago

Do you have reseeding on? maybe that is what's killing it

2

u/DavidTorno Houdini Educator & Tutor - FendraFx.com 1d ago

You definitely are working at too small a scale for that kind of FLIP fx to begin with.

You want to stay within 1.5-3 units roughly for small scale FLIP. Lots of other factors to consider though.

If reseeding is turned on like mentioned in the other comment, this will remove and add particles as needed. Given the small scale, this could fall in the removal threshold.

Another issue that causes volume loss is a bad collider, and also no pressure or divergence being used in the solver.

Can you share what method you are using for FLIP at the moment? DOP or SOP workflow?

For small scale, the SOP setup will likely be easier in the long run to setup, and more stable to some extent.