Edge Collision

Edge Collision

The Edge Collision behavior is ideal for setting up complex motion simulations with objects that do not exit the Canvas. Objects with the Edge Collision behavior applied 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. Edge Collision has no effect on objects larger than the Canvas.

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.

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 farther 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 Inspector to fit the bounding box as closely as possible to the edge of the image.

Adjust this behavior using the controls in the Behaviors Inspector:

  • Affect Subobjects: A checkbox, available 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 enclosed in the parent object are affected individually. When this checkbox is deselected, all objects enclosed in the parent object are affected by the behavior together.

  • Bounce Strength: A slider that sets the speed at which objects travel after colliding with an edge. A value of 0 causes objects to come to a complete stop when colliding with an edge that’s perpendicular to the direction of motion. Higher values cause an object to move faster after bouncing. This parameter only slows the object in the direction perpendicular to the bounced edge.

  • Active Edges: Six checkboxes that define which collision box edges are detected by the Edge Collision behavior. You can turn edges on and off in any combination.

    • Left Face: Defines the left edge for the collision.

    • Right Face: Defines the right edge for the collision.

    • Top Face: Defines the top edge for the collision.

    • Bottom Face: Defines the bottom edge for the collision.

    • Back Face: Defines the back edge (in Z space) for the collision.

    • Front Face: Defines the front edge (in Z space) for the collision.

  • Width: A slider that sets a width (the right and left edges of the Canvas) other than the size of project. By default, Width is set to the project size.

  • Height: A slider that sets a height (the top and bottom edges) other than the size of project. By default, Height is set to the project size.

  • Depth: A slider that sets a depth (the back and front faces, in Z space) for the edge collision. By default, Depth is set to 100 pixels.