Apple Motion 3 - Manual (Page 694)

694 Chapter 8 Working with Particles
Once an emitter is added to the project, the following occurs:
 An emitter appears in the Layers tab and is selected.
 A cell containing the image to be “particle-ized” appears underneath the emitter.
 The original source layer (the cell source) is disabled.
Note: Changes made to the original source layer, such as opacity or shearing, are
respected in the particles even after the emitter is created.
 In the Canvas, the emitter bounding box appears, which can be transformed using
the onscreen controls.
 The first particle appears in the Canvas in the same location as the original layer.
Although it appears as if the particle is selected, the bounding box represents the
emitter.
 The Emitter HUD is displayed. If you have hidden the HUD, press F7.
Note: For projects with a frame rate greater than 30 frames per second (fps), at times
only the bounding box (not the first particle) may appear at the first frame of your
project. Because, by default, particles are generated at 30 particles per second, there is
no guarantee that a particle will appear on every frame.
By default, the first frame of a new particle system (with a single cell) has one particle. If
you play your project, additional particles are generated and emerge from the center of
the emitter.
Particle system at frame 1