Apple Motion 5.1.1 - Manual (Page 548)

Chapter 14 Particles 548
Particles behavior parameters
After you apply the Scale Over Life or Spin Over Life behavior, you can adjust its parameters in
the Behaviors Inspector.
Scale Over Life parameters
This Scale Over Life behavior has one main parameter control and three optional parameter
controls that vary, depending the selected Increment Type:
•
Increment Type: Choose an option from this pop-up menu to determine which method is used
to resize particles over their lifetime. 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. When
Natural Scale is selected, the Scale At Birth and Scale At Death parameters become available.
•
Rate: Specifies a steady rate at which particles change size over their entire lifetimes. When
Rate is selected, the Scale Rate parameter becomes available.
•
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 pre-existing particle Scale (defined in the Cell
Controls section of the Emitter Inspector). When this option is selected, the Scale At Birth
and Scale At Death parameters become available.
•
Custom: This mini-curve editor customizes the scale of the particles over their lifetime. Click
the disclosure triangle to display the mini-curve editor in the Inspector. For more information
on using mini-curve editors, see
Mini-curve editor on page 482.
•
Scale At Birth: Determines the initial size of particles when they are created. This parameter
appears when Natural Scale or Birth and Death Values is selected in the Increment Type
pop-up menu.
•
Scale At Death: Determines the size of each particle at the end of its lifetime. This parameter
appears when Natural Scale or Birth and Death Values is selected in the Increment Type
pop-up menu.
•
Scale Rate: Defines how quickly each particle changes size. Positive values grow particles over
time, while negative values shrink particles over time. This parameter appears when Rate is
selected in the Increment Type pop-up menu.
•
Custom Scale group: This group of parameters (a mini-curve editor and two sliders, described
below) appears when Increment Type is set to Custom. Use the mini-curve editor for more
precise control over the Scale of particles in your particle system.
•
Custom Scale: Use this slider to adjust the value of the selected keyframe in the mini-
curve editor. This parameter appears when Custom is selected in the Increment Type
pop-up menu.
•
Over Life: Use this slider to adjust the position of the selected keyframe in the life of
the particle. This parameter appears when Custom is selected in the Increment Type
pop-up menu.
The HUD contains the Increment Type pop-up menu, and the Scale Rate, Scale At Birth, and Scale
At Death parameters.
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