5

Anatomy of a Particle System
Every particle system is made up of an emitter and one or more particle cells. Each cell
appears as a sublayer underneath the emitter in the Layers list and the Timeline (click
the disclosure triangle beside the emitter layer to hide or reveal its sublayers).
Emitter
Original object (disabled)
Cell (with behaviors
applied)
The emitter and cells have separate sets of parameters that control the particle system’s
behavior. If you imagine that a garden hose is a particle system, the nozzle acts as the
emitter, while the water represents the flow of particles. Changing the parameters of the
emitter changes the shape from which the particles are emitted and their direction, while
changing the cell’s parameters affects each particle.
By changing a few parameters, it’s possible to create different effects using the same cell.
Note: In a particle system, cells and particles are not the same thing. A cell is a layer (in
the Layers list) that acts as the “mold” for the particles (the multiple objects generated
in the Canvas). The cell itself is a copy of a source object (cell source) that appears dimmed
(disabled) in the Layers list, and therefore is by default not visible in the Canvas.
As with any effect in Motion, particle system parameters can be keyframed to change a
particle effect’s dynamics over time. For example, you can create a path of bubbles that
follows an object onscreen by keyframing the emitter’s Position parameter. For more
information on keyframing, see Keyframes and Curves.
669Chapter 14 Working with Particles