Apple Motion 4 - Manual (Page 505)

Edge Collision
This is a good behavior to use if you’re setting up complex motion simulations and you
don’t want your objects exiting the Canvas. Objects with the Edge Collision behavior
applied either come to a stop or bounce off after colliding with the edge of the Canvas
frame. For example, if you apply the Throw behavior to an object and set the velocity to
send the object toward the edge of the frame, then apply Edge Collision, the object will
bounce off the edge of the frame according to the Bounce Strength parameter.
Animation path of a
thrown object affected
by the Edge Collision
behavior
The angle at which the object bounces depends on the angle at which it hits the edge
of the frame; the speed it travels after bouncing is set by the Bounce Strength parameter.
Note: Edge Collision has no effect on objects that are larger than the Canvas.
Important: By default, the Edge Collision behavior uses the size of the project and the
bounding box to determine how the object collides with the edge of the Canvas. For
example, in an NTSC Broadcast SD project (720 x 486 pixels), an object bounces off the
right and left edges of the project at its bounding box. With groups (particles, text, and
objects), only the object’s center is used. You can make the object travel further off the
Canvas before it bounces by adjusting the Width and Height parameters. If you’re using
this behavior with an object that has an alpha channel that’s smaller than its bounding
box, adjust the Crop parameter in the object’s Properties tab to fit the bounding box as
closely as possible to the edge of the image.
Parameters in the Inspector
Affect Subobjects: This parameter appears when this behavior is applied to an object
that contains multiple objects, such as a group, a particle emitter, a replicator, or a text
layer. When this checkbox is selected, all objects within the parent object are affected
individually. When this checkbox is deselected, all objects within the parent object are
affected by the behavior together, as if they were a single object.
505 Chapter 9 Using Behaviors