5.1.1

Chapter 9 Behaviors 353
Simulation behaviors
Simulation behaviors overview
Simulation behaviors perform one of two tasks. Some Simulation behaviors, such as Gravity,
animate the parameters of an object in a way that simulates a real-world phenomenon. Other
Simulation behaviors, such as Attractor and Repel, aect the parameters of objects surrounding
the object to which they’re applied. These behaviors allow you to create sophisticated
interactions among multiple objects in your project with minimal adjustments. Like the Basic
Motion behaviors, Simulation behaviors also aect specic object parameters. Examples include
Attractor, Gravity, and Repel.
Important: Several Simulation behavior parameters contain object wells into which you drag
target objects used as attractors, repellers, orbiters, and so on. Dragging an object to a well can
be tricky—be sure to click the object name in the Layers list and immediately drag the object
to the object well (without releasing the mouse button). The behavior must remain active even
though you are dragging another object in the Layers list. If you click the object in the Layers list
and release the mouse button, that object becomes selected, and the behavior’s parameters are
no longer displayed. This applies to all wells, including mask source wells and image wells.
For a description of each Simulation behavior, see the behavior list in the Help table of contents
(the sidebar to the left of this window).
Align to Motion
The Align to Motion behavior changes the rotation of an object to match changes made to
its direction along an animation path. This behavior is meant to be combined with Simulation
behaviors that animate the position of an object or with a keyframed animation path you
create yourself.
Note: The Align to Motion behavior does not work on objects animated using the Motion Path
behavior. Instead, use the Snap Alignment to Motion behavior (in the Basic Motion subcategory).
Before
After using Align to Motion
Unlike the Snap Alignment to Motion behavior, which produces absolute changes in rotation
that precisely match changes in direction, Align to Motion has a springy reaction and creates a
more lively eect.
In the above example, the airplane travels along the keyframed animation path, but the plane
isn’t aligned to the animation path (notice the rotation handle). Using the Align to Motion
behavior, the airplane’s angle of rotation moves so it points in the direction of the animation
path. By adjusting the Drag parameter, you can make the object careen wildly about its anchor
point as it goes around curves in the animation path.
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