A node I added to the network seems to have no effect
Possible causes and solutions:
The cook flag is on a node higher up or on a different branch of the network.
To fix this simply set the cook flag on or after the node whose effect you want to see in the viewer.
The node’s Activation parameter is (or evaluates to) 0.
Check the value of the node’s Activation parameter. If it is an expression, make sure it evaluates to a value other than 0.
Particles escape my [Icon:POP/collision][Collision POP|Node:pop/collision]
The movement of the particles is larger than the distance within which Houdini can detect collisions, so the particles move right through the “wall”.
If you are trying to keep particles inside geometry that is moving or rotating, remember to set Hint on the Collision tab to Translating Geometry.
Increase the Collision tolerance. This makes the particle look farther away to see if it has “hit” something.
On the Behavior tab, increase the Oversampling. This makes the simulation move the particles in finer-grained steps, which increases the likelihood of detecting a hit.