Using Masks with Particle Systems
As shown in the following images, you can apply masks to the cell source of a particle
emitter. The effect of the mask on the cell source is carried through to the emitted particles.
Original source layer
Bezier mask applied
to source layer
Resulting particle system
Working with Particles
You can also apply masks to the emitter object itself.
Rectangle mask (inverted)
applied to the emitter object
For more information on working with masks, see
Masking a Layer or Group