Hello!

I am doing a vellum grain simulation and I am having some issue with the collisions.
The grains should stay inside the machine (wire mesh around the sim), but as you can see in the image below quite a few of them escape the mesh.


This is especially true for the two of the 3 cylinders... maybe it has something to do with the collision mesh? This is how the collision mesh tree looks like


I also tried increasing the substeps of the sim into the vellum solver node, but I didn't notice any significant difference.

Any tips on what to do to fix the problem?


Thank you!
Bernardo

Hey Bernardo,

It's easier to help when you post your file. with all incoming geos stashed.
Depending on how your collision geo is represented inside the dops network.
If it's a volume you should increase the Uniform Divisions. Or increase the thickness of your collider.

Cheers
CYTE

Hey CYTE, thanks for you answer! There's quite a lot of external objs and alembic files, few of them quite big, which are needed for the file. Do you know if there's a way to pack them or do I have to manually put them in a zip when I send the file?

By the way, I've solved the issue!

2 things helped
- I think the collision mesh was too messy. I guess houdini didn't like too many stretched ngons. I thought houdini automatically remeshed the geometry, but maybe I am wrong? Either way, I exported a remeshed version of the collision geometry from blender (I know I could've done it in houdini, but I wanted a quick check and I am much more proficient in blender than in houdini).
This fixed most of the escaping grains.




- To fix the few remaining grains I've created an "encapsulating" version of the collision geometry and I fed it into a pop kill node, so that basically any grain escaping the collision object was killed.



Seems to be work well now!