Vary emission from different points of point emitters

User Guide > Dynamics and Effects > Dynamics > Particles > Work with emitters >

You can use a different emission rate for each particle, CV, vertex, edit point, or lattice point of Omni or Directional point emitters. For example, you can emit a ring of fire from a circle’s edit points and vary the emission at each point to enhance the irregularity found in natural fire. You cannot vary emission on a per-point basis for objects whose Emitter Type is either Surface or Curve.

TipIf you emit from a particle object, you can use an expression or MEL command to obtain the id of all particles that emit the particles. You can use the id to query the emitting object’s attribute values, for example, acceleration, velocity, and finalLifespanPP. To do this, you must add the parentId attribute to the emitted particle shape node.

Note that if you use the MEL emit command to create the particles that emit, the parentId attribute of those emitted particles is always 0.

To vary emission from particles

Create and select the emitting particle object.
Select Particles > Per-Point Emission Rates.
This creates an attribute named emitterRatePP for the particle object that emits. This attribute lets you vary emission rates on a per particle basis.
In the Attribute Editor, open the Per Particle (Array) Attributes section.
Without breaking the connection to emitternameRatePP, right click the emitterNameRatePP box and select the desired method to set its value. See Set attributes on a per particle basis.
Note that you can turn the emitter’s Use Per-Point Rate attribute on or off to toggle per-point emission rates. In the Outliner, the emitter is indented under the emitting object.

To vary emission from a NURBS or polygonal point emitter

Finish modeling the geometry before adding a point emitter.
Select the emitting geometry.
Select Particles > Per-Point Emission Rates
Select the emitting object’s shape node.
In the Extra Attributes section of the Attribute Editor, open the emitterName Rate PP section.
For the emitterNameRatePP attributes, enter values in the Attribute Editor boxes corresponding to the CVs, vertices, edit points, or lattice points. To learn which box corresponds to a point, experiment with a large value in a box. You can also use an expression, ramp, or Artisan to set individual rates.

NoteIf you add CVs, vertices, or edit points after you add and tune per-point emission rates, you can select Per-Point Emission Rates a second time to set the additional entries for emitterNameRatePP. However, the Attribute Editor emitterNameRatePP entries no longer correspond to the same identifiers for CVs, vertices, or edit points. You’ll need to correct the emitterNameRatePP entries.
If you delete CVs, vertices, or edit points, delete the emitter, create a new emitter, and choose Per-Point Emission Rates again.