tips mainly for Houdini


Split collision objects into small objects
In this case, a original collision object are cut in "mountain" node.
Packed each piece so we can keep only where we need.
Avoid infinite loop

To get particles for collision objects, use "Dop Import" and tick "Do Not Trigger Simulation" (right one of the network view).
We can get actual particles to use for something, use another "Dop Import" without tick there (left one of the network view).