Apple Motion 5.1.1 - Manual (Page 544)

Chapter 14 Particles 544
Particle Emitter Timing controls
When you create a particle system, its duration can be as long or short as necessary, regardless
of the duration of the original source objects used to create the particle system. The duration of
a particle system is defined by the duration of the emitter object. Changing the In or Out point
of an emitter in the Properties Inspector, Timeline, or mini-Timeline changes the duration of the
entire particle system.
By default, particles are generated by every cell in a system for the duration of the emitter. The
duration of each generated particle is defined by the Life parameter of the cell that generated it,
and not by the duration of the cell itself.
The duration of the cell controls the duration over which new particles are generated. You can
change a cell’s duration by dragging its position or its In and Out points in the Timeline. In this
way, you can adjust the timing that defines when each cell’s particles emerge.
For example, you can create a particle system that simulates an explosion by offsetting the
appearance of three types of particles. First, dense white sparks emerge from the center. Half a
second later, more diffuse orange blast particles appear around a larger area. One second after
that, hot smoke emerges from underneath both of these layers as they fade away.
You can offset a cell in the Timeline or mini-Timeline so that the cell starts before the emitter.
This creates a “pre-roll” in which the particle simulation begins before the particles are drawn.
For more information on adjusting the timing of layers in the Timeline, see Timeline overview on
page 251.
Create graphics for particle systems
Create still-image graphics to use as particle cells
Creating a particle system from scratch begins with designing the particles you want it to emit.
You can use any image, shape, text, or movie supported by Motion as a source for a cell.
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