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140 Chapter 4 Arts and Letters
As with any object in Motion, you can keyframe the particle emitter and particle cell
parameters. For example, you can keyframe the position of a particle emitter so that
the emitter moves across the screen spreading sparkles like a magic wand.
Particle Systems
Motion particle systems use objects, referred to as cells, as the mold for the particles
that are generated by the emitter. You can use nearly any object in Motion as a source
for a particle cell. Each particle that is created is essentially a duplicate of the original
cell, and is animated according to the parameters for that particle system (a particle cell
or cells and emitter).
The particle emitter and particle cells have separate tabs in the Inspector, each with its
own set of parameters that work together to control how the particle system acts. 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 direction and number of particles that are created, while changing
the cell’s parameters affects each individual particle.
You can apply Simulation behaviors to particle emitters or particle cells. A Simulation
behavior applied to a particle cell affects each particle the cell generates. A Simulation
behavior applied to a particle emitter can affect only the emitter, or all generated cells.
Whoa. For example, you can apply the Gravity behavior to an emitter so that only the
emitter falls, or so that all particles fall.
Simple shape (star) object Shape as particle cell source
2505.book Page 140 Wednesday, June 30, 2004 5:58 PM