Creating the nParticle sparks is the final stage to the two-part particle effect. The nParticle sparks are emitted from the nParticle_sparks_emitter object at various locations along the chute using Emit From Object. An external gravity field is added to give the sparks an arcing motion as they fly up and fall to the foundry floor.

You also add two more Exclude Collide Constraints so that the sparks do not collide with the slag or the nParticle _sparks_emitter objects.

To emit the nParticle sparks

1. In the Outliner, select the nParticle_sparks_emitter object and select nParticles > Create Options > Point.
2. Select nParticles > Emit from Object > .
3. In the Emitter Options (Emit from Object) window, select Edit > Reset Settings and do the following:
   • For the Emitter name, type emitter_sparks.
   • If the Solver list appears, ensure that it is set to nucleus1.
4. In the Basic Emitter Attributes section, set the following:
   • Rate (particles/sec): 100
   • Cycle emission: Frame (timeRandom on)

     When Cycle Emission is set to Frame, the emission sequence is restarted after the number of frames specified by Cycle interval. For this effect, Cycle interval is left at 1, so the emitted sparks cycle restarts each frame.

5. In the Basic Emission Speed Attributes section, set the following:
   • Speed: 10.0
   • Speed random: 100.0
   
6. Click Create.
7. In the Outliner, rename the new nParticle object to nParticle_sparks.
8. Rewind and play the simulation.

   Notice again that the new nParticle system collides with the slag, breaking the mesh apart. To solve this, you add two more Exclude Collide Pairs constraints.

   
9. In the nParticle_slag object's tab in the Attribute Editor, turn off Intermediate Object.

   You can now select the nParticle object for the nConstraint.

10. In the Outliner, Ctrl-select the geo_slag and nParticle_sparks objects, then select nConstraint > Exclude Collide Pairs.

    Name this constraint dynConstraint_slag_sparks.

11. Add another Exclude Collide Pairs constraint between the nParticle_sparks_emitter and nParticle_sparks objects. Name this constraint dynConstraint_sparksEmitter_sparks.
12. Rewind and play the simulation.

    The particle systems no longer collide, but the nParticle_sparks need adjustments to make them look and behave like red-hot sparks.

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