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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 to start before the emitter. This
creates a “preroll” in which the particle simulation starts before the particles are drawn.
For more information on adjusting the timing of layers in the Timeline, see Using the
Timeline.
Creating Graphics and Animations for Particle Systems
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. This section presents guidelines for creating particle imagery.
Creating Still Image Graphics for Particle Systems
Particle systems that use still images as their cell sources render in real time much faster
than systems that use video or animation clips. A still image is often all you need to create
a compelling particle system. Here are some guidelines for creating graphics for use as
particles.
688 Chapter 14 Working with Particles