# Creating the nParticle collision event

A collision event involves a source particle system (the object that executes an event when it collides with collision geometry) and a target particle system (the particle system that emits particles when the event is executed). For this collision event, the nParticle_sparks object is the source particle system, the nRigid_chute is the collision geometry, and the nParticle_sparks_emitter is the target particle system.

For more information about Particle Collision Events, see Work with nParticle collision events in the nParticles section of the Maya Help.

To create the collision event

1. In the Outliner, select the nParticle_slag object, then select nParticles > Particle Collision Event Editor.
2. In the Particle Collision Event Editor, do the following:
   - Ensure that nParticle_slag is selected in the Objects panel.
   - For Set event name, type Sparks_Emission.
   - In the Event type section, set Type to Emit.

     In this case, when the Event type is Emit, the source particle object continues to live after the collision event. When set to Split, the object dies after the event.

   - Set Num particles to 1.

     This specifies that one particle is created for each collision event.

   - Set Spread to 1.

     This sets the emission spread angle to 180 degrees.

   - For the Target particle, type nParticle_sparks_emitter.

     This specifies that the collision event creates an nParticle object.

   - Set Inherit Velocity to 0.

     This sets new nParticles to not inherit velocity from the nParticle_slag object.

   - Click Create Event and close the Particle Collision Event Editor.

   The new nParticle object appears in the Outliner.

3. Rewind and play the simulation.

   A new Balls style nParticle system is created (since Balls was the last nParticle style selected in lesson 1) when the nParticle_slag collides with the nRigid_chute object. Notice the nParticles are colliding with the slag and breaking it apart. To stop the collisions between the nParticle_sparks_emitter and nParticle_slag, you will create an Exclude Collide Pairs constraint.

   NOTE:If you do not see the new nParticle system emitting into the scene, ensure that you have disabled the nParticle_slag cache, and create the collision event again.