You can use the Particle Collision Event Editor to create and edit specific events to occur when nParticles collide with other Nucleus objects. AA collision event involves an original particle system, which is the object that executes an event when it collides with another object, and a target particle system, which is the particle system that emits particles when the event is executed. You can specify an existing nParticle system as a target for the collision event. Otherwise, a new nParticle system is created when the collision event is created. See Create particle collisions.

Using collision events in your nParticle effects lets you can combine particle systems, emit new particles into particle systems in the advanced frames of a simulation, and accurately kill particle systems when they collide.

When you use nParticles in collision events, be aware that nParticles emitted from the target object can collide with other nParticles, causing collision events to execute prematurely.

To avoid unwanted nParticle collisions, you can turn off the Collide attribute on the target object. See Collide. You can also use the Collide Strength and Collide Strength Scale attributes to dampen or delay collisions on the target object. See Collide Strength and Collide Strength Scale.

When creating particle collision events using nParticles, be aware of the following:

• The collisionGeometryIndex output attribute is not supported for nParticle collision events in Maya 2011.
• nParticle collision events pass the name of the Nucleus object that the nParticles are colliding with to the event callback rather than passing the geometry's name.
• The Nucleus ground plane cannot be the target of an nParticle collision event.