You can add behaviors to a particle system’s emitter, or to the cells themselves, to achieve sophisticated, organic effects with very little effort. You can animate any emitter using Basic Motion, Parameter, or Simulation behaviors. Emitter parameters and cell parameters can also be animated via keyframes. If you animate emitter-specific parameters such as Emission Angle or Emission Range, the position and distribution of new particles generated by that emitter are animated. All animation occurs relative to the duration of the emitter.
Animating an emitter’s Properties Inspector parameters is useful for altering the position and geometric distribution of a particle system over time. Keyframing an emitter’s Position parameter moves the source of newly emitted particles without affecting any particles generated at previous frames, creating a trail of particles.
Keyframing an emitter’s Emitter Inspector parameters is a good way to modify the particle system’s overall characteristics over time, such as increasing or decreasing the size, speed, or lifetime of newly generated particles.
Particles also have their own category of behaviors. The Particles behaviors include Scale Over Life and Spin Over Life, which allow you to modify and animate the rotation and size of the particles over their lifetime.
Using the Motion Tracking behaviors, you can apply existing tracking data to an emitter or track an emitter to a clip. For more information on using the Motion Tracking behaviors, see Motion Tracking.
For an example of a keyframed emitter object in a particle system, see Example 2: Creating Animated Pixie Dust. For more information on keyframing parameters in the Keyframe Editor, see Keyframes and Curves.
Applying behaviors to emitters is a quick and easy way to move emitters in your project. Attaching the Motion Path and Snap Alignment to Motion behaviors to an emitter affects the position of the source of all new generated particles. Throw and Spin affect the position and rotation, respectively, of the emitted particles, unless Affect Subobjects is deselected.
With all Basic Motion behaviors, after individual particles emerge, they’re unaffected by changes to the position of the emitter. This means that moving the emitter around the screen using behaviors results in the creation of a trail of particles that behave according to their particle cell parameters.
Note: You can override this effect by increasing a cell’s Attach to Emitter parameter value (in the Cell Controls group of the Emitter Inspector).
Drag a behavior from the Library onto an emitter in the Canvas, Layers list, or Timeline.
The behavior is applied to the emitter, which begins to move according to the parameters of the behavior.
Note: Not all behaviors instantly activate an object when applied. For example, when a Throw behavior is applied to an object, the Throw Velocity parameter must be adjusted before the object moves.
Simulation behaviors applied to cells are in turn applied to each particle generated from that cell. This can result in some extremely complex animations as dozens of particles move according to the behaviors you’ve defined. Behaviors applied to cells have no effect on the position of the emitter. Parameter behaviors on a cell only affect particles when they are created.
Drag a behavior from the Library to a cell in the Layers list or Timeline.
The behavior is applied to the cell, and all particles generated from that cell begin to move according to the parameters of the behavior.
Tip: If you do not see your expected result when applying behaviors to particle cells, try selecting or deselecting the Affect Subobjects checkbox (in the Behaviors Inspector) or selecting a different option from the Affect pop-up menu in the HUD or Behaviors Inspector. These parameters determine whether the entire object (such as the particle emitter) or its components (such as the particle cells) are affected by the behavior and how an object interacts with surrounding objects, respectively.
Note: The Affect Subobjects checkbox only appears in the Behaviors Inspector when the Throw and Spin behaviors are applied to a group that contains multiple objects, such as a group, particle emitter, or text.
As with all objects in Motion, you can apply Parameter behaviors to the parameters in the Emitter or Particle Cell Inspector.
Drag a behavior from the Parameter category in the Library onto an emitter or cell in the Layers list or Timeline. In the Apply To section of the Behaviors Inspector or HUD, choose an option from the Go pop-up menu.
Select an emitter or cell in the Layers list or Timeline, then choose a Parameter behavior from the Add Behavior pop-up menu in the toolbar. In the Apply To section of the Behaviors Inspector or HUD, choose an option from the Go pop-up menu.
In the Emitter or Particle Cell Inspector, Control-click a parameter, then choose a Parameter behavior from the shortcut menu.
The Particles category in the Library contains two behaviors specifically for use with the cells or emitter in a particle system:
This behavior lets you grow or shrink 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.
The HUD contains the Increment Type pop-up menu, and the Scale Rate, Scale At Birth, and Scale At Death parameters.
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.
The HUD contains the Increment Type pop-up menu, and the Spin Rate, Spin At Birth, and Spin At Death parameters.