Apple Motion 5.1.1 User Manual
Page 515
Chapter 14
Particles
515
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 as well as their direction. Changing the cell’s
parameters affects each particle.
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
on page 439.
You can also track an emitter to a moving object in a clip, or apply existing tracking data in your
project to an emitter. For more information on using the Motion Tracking behaviors, see
on page 955.
Additionally, you can add behaviors to each cell or to the emitter to create even more varied
effects (simulation behaviors can be especially effective). Any behavior that you apply to a cell
is in turn applied to each particle it generates. This lets you achieve almost limitless variation.
Adding behaviors to cells in addition to the particle system’s own parameters is an easy way to
create complex, organic motion that would be impossible to accomplish any other way. You can
also apply a behavior to another object in your project (an object that is not part of the particle
system). For example, applying the Repel behavior to an object will cause particles to weave
around that object. For more information about behaviors, see
on page 293.
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 not visible in the Canvas. Almost any object in Motion can be used
as a cell source, including shapes, text, images, image sequences, and clips. Transformations
that you apply to the source are respected in the cell layer, which in turn propagates those
transformations to the particles generated in the Canvas. For example, if you use a rectangle
shape that is sheared and rotated as the cell source, particles created using that rectangle as the
cell source are sheared and rotated.
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