5.5

532Motion User Guide
Apply a Particles behavior to an emitter or cell
The Particles category of behaviors in the Library contains two behaviors specifically for
use with the cells or an emitter in a particle system:
• Scale Over Life: This behavior lets you grow or shrink the particles in a system over the
duration of each particle’s life.
• Spin Over Life: This behavior lets you spin the particles in a system over the duration of
each particle’s life.
In Motion, do one of the following:
• Drag a behavior from the Particles category of behaviors in the Library onto an emitter
or cell in the Layers list or Timeline.
• Select an emitter or cell in the Layers list or Timeline, click Behaviors in the toolbar,
then choose a behavior from the Particles submenu.
For a description of each Particles behavior parameter, see Scale Over Life controls in
Motion and Spin Over Life controls in Motion.
Particles behavior controls
Scale Over Life controls in Motion
The Scale Over Life behavior has one main parameter control and three optional parameter
controls that vary, depending on the selected Increment Type:
• Increment Type: A pop-up menu that sets the method used to resize particles over their
lifetimes. There are four options:
• Natural Scale: Specifies starting and ending scale percentages used to animate each
particle’s size over its lifetime. Natural Scale uses an exponential curve to allow
the animation to progress slowly when the scale values are small, and speed up
when the values are large. This creates the illusion that the scaling is occurring at a
constant speed.
• Rate: Specifies a steady rate at which particles change size over their lifetimes.
• Birth and Death Values: Specifies starting and ending scale percentages used
to animate each particle’s size over its lifetime. The scale amount generated by
this option for a specific particle at a specific time is multiplied by the preexisting
particle Scale (defined in the Cell Controls section of the Emitter Inspector).
• Custom: Lets you customize the scale of the particles over their lifetimes with a
mini-curve editor (described below).
Scale At Birth: A slider (available when Increment Type is set to Natural Scale or Birth
and Death Values) that defines the initial size of particles when they’re created. Click
the disclosure triangle next to the Scale At Birth parameter to reveal separate X, Y, and
Z subparameters. Use X and Y to change the width and height of generated particles;
use Z to change the depth of 3D text particles.
• Scale At Death: A slider (available when Increment Type is set to Natural Scale or Birth
and Death Values) that defines the size of each particle at the end of its lifetime. Click
the disclosure triangle next to the Scale At Death parameter to reveal separate X, Y, and
Z subparameters. Use X and Y to change the width and height of generated particles;
use Z to change the depth of 3D text particles.