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• 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 allows you to customize 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.
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: Allows you to define 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: This group of parameters appears when Increment Type is set to Custom.
Use this 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.
HUD Controls
The HUD contains the Increment Type pop-up menu, and the Scale Rate, Scale At Birth,
and Scale At Death parameters.
Spin Over Life
This behavior lets you spin the particles in a system over the duration of each particle’s
life. It has one main parameter and three optional parameters that appear depending on
the selected Increment Type.
Parameters in the Inspector
Increment Type: A pop-up menu that determines which method is used to spin particles
over their lifetime. There are three options:
• Rate: Specifies a steady rate and direction in which particles spin over their lifetime.
When Rate is selected, the Spin Rate parameter becomes available.
719Chapter 14 Working with Particles