Houdini 16.5 Particles

Reacting to events

Various particle operators can create "events" when something happens, such as a collision, or a value passing some threshold. An event can trigger the activation of other particle operators, allowing for complex and interesting behaviors.

Downstream you can use the popevent function to detect a named event. This is very useful in the Activation parameter of a POP node, where you can trigger the node only if the event has fired.

Events are identified by a name string.


The info button on the POP node’s tile gives information on which events are currently occurring.

Operators that generate events

Collision POP

When particles collide with geometry.

Limit POP

When particles go outside a boundary.

Event POP

Defines expressions that generate events when they evaluate to non-zero for an input particle.


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