In the second step of creating an nParticle effect, you convert the meshes you want the nParticles to collide with to passive collision objects. When nParticles collide with passive collision objects, their behavior, speed, and direction change. Passive collision objects are not affected by collisions with other objects.

In this lesson, you convert the candy package, bowl, and the desk surface geometry to passive collision objects. The nParticles can then collide with these objects.

To convert geometry to passive collision objects

1. Rewind the simulation to the start frame.
2. In the scene view, -select the package and bowl meshes as well as the surface of the desk.
   
3. Select nMesh > Create Passive Collider > .

   The Make Collide Options window appears.

   
4. From the Solver list, select nucleus1.
5. Click Make Collide.

   The candy package, bowl, and desk surface meshes are converted to passive collision objects. nRigid handles appear at the center of the meshes in the scene view. You can use the nRigid handles to quickly select nRigidShape nodes in the Hypergraph or their tabs in the Attribute Editor.

   These objects are now members of the same Nucleus system (nucleus1) as the nParticles.

6. To rename the nRigid objects, in the Outliner, double-click them one at time and type nRigid_Package, nRigid_Bowl, and nRigid_Desk respectively. Press after you type each object name.
   
7. Play the simulation.

   When you play the simulation, the nParticles now fall from the end of the package and are collected in the bowl.

   Notice that the nParticles are not falling from the candy package as quickly as you might expect. Instead, they fall slowly, as if the simulation was playing back in slow motion. This is because the Nucleus solver properties need to be adjusted to suit the simulation.

   In the next section of the lesson, you set Nucleus solver properties so that the particles fall realistically.