[Solved] Drastic FLIP volume change with feedback on rigid bodies

[meepzh]

Hey everyone,

My overall goal is to simulate liquid poured into a glass with ice cubes inside, with the ice cubes floating.

Everything works normally until I enable feedback forces:

• Normal: https://gfycat.com/LameCarelessIzuthrush
• With feedback: https://gfycat.com/FlashySolidFreshwatereel

There's a ton of particle loss. For these sims, particle separation is 0.004, grid scale is 2, feedback force is 1, and max FLIP substeps is 10.

The best I got was to maintain volume with 1.75 grid scale, but with overreacting ice cubes: https://gfycat.com/MiserlyEmbarrassedAfricanbushviper
I've attached the Houdini file for this below.

Anything related to this problem would be helpful. Why is there particle loss, even without reseeding or with many substeps (I've tried using 20)? Is there a problem with how I'm using feedback? Why does changing grid size cause volume to increase or decrease?

Thanks!

ice-tea-milk_027_017.hipnc

Edited July 19, 2017 by meepzh
solved!

[Sepu]

For one you scene scale is pretty small. Second the feedback scale, you need to play with this setting it will react appropriately, again depending of you scene scale. 
For good measure use the pig as an example as how you scale should be. 

Here is a fix version.

 

ice-tea-milk_027_017_FIX.hipnc

Edited July 19, 2017 by Sepu

[meepzh]

Thank you very much! I owe you for all the time you've saved me.

I thought I could make it work with an accurate scene scale, but this still looks realistic. For others, Sepu had bumped up my cup size from 25cm to 750cm and lowered feedback scale from 1 to 0.75.

I tried only lowering the feedback scale, but it seems like the root cause was the scene scale.

Again, thank you!

Edit: Actually, the sloshing around in the cup gives away the scene scale, but I imagine playing with the forces and velocity smoothing will fix that.

Edited July 20, 2017 by meepzh