Simulation wrapped in HDA causes floating objects

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Hello,

I have an HDA setup with a material fracture and bulletsolver sim that I'm using in unreal to fracture and simulate objects. I use it with a scriptable tool blueprint and trigger cook and changes from there.

It works fine the first time I simulate but if I change the seed I get floating pieces. I have it set up with a timeshift which I suspect isn't the best way. I have the same problem in houdini, if I change the seed. If I manually reset the simulation in houdini it looks good again. Is there a better way to set this up?

I tried resetting the sim from an unreal parameter connected to a python script to press the reset button, it works well in houdini but in unreal I ended up with no output from the sim after several tests.

I attached a test hda, there is the same problem with floating pieces when changing the seed in houdini, I haven't worked much with simulations so I suspect there is a more fool-proof way to set this up! I want to avoid local cache as people across an unreal project will be using it.

Edited by stinzen - 2026年6月18日 08:44:18

Attachments:
hda_simulationtest_01.hda (118.7 KB)
floating_seed_change.png (441.8 KB)

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