# Creating the nConstraint

For this simulation, you want both nParticle systems (nParticle_slag and nParticle_sparks_emitter) to interact with the chute, but you do not want the two nParticle systems to collide. Since both nParticle systems need to interact with the chute, you cannot disable collisions on either nParticle object or assign each system its own Nucleus solver. Creating an Exclude Collide Pairs constraint is the best solution for this simulation, because it lets you disable collisions between objects or object components.

To create an Exclude Collide Pair constraint

1. In the Outliner, Ctrl-select the nParticle_sparks_emitter and nParticle_slag objects, then select nConstraint > Exclude Collide Pairs.

   A dynamicConstraint1 object appears in the Outliner.

2. Rename the new constraint to dynConstraint_slag_sparksEmitter.
3. Rewind and play the simulation.

   The two nParticle systems no longer collide with each other. Leave the dynamicConstraintShape node attributes set to the default values for this simulation.

4. Select the nParticle_slag object, and in the Attribute Editor, turn on Intermediate Object to hide it from the scene.

   Hiding the nParticle slag makes it easier to see the how the nParticles sparks work in the scene.

   In the next section, you refine the behavior for the nParticle_sparks_emitter object and complete the second stage of the sparks effect.