Apple Motion 4 - Manual (Page 913)

To increase or decrease the effect of the flicker, you can modify the Randomize parameters.
To quickly jump to the Randomize parameters from the Generator tab, click the Behaviors
icon, then choose Randomize from the pop-up menu.
For more information on using Parameter behaviors, see Parameter Behaviors .
Using Generators as Particle Cell Sources
Like other objects, generators can be used as a source for particle cells. The following
example uses the Soft Gradient generator. It is recommended that you scale the generator
down in the Generator tab of the Inspector to give your particle system more flexibility
and to keep the project from taking too much processing power.
913 Chapter 15 Working with Generators