2

820 Chapter 12 Using Shapes and Masks
The Difference Between Shapes and Masks
Shapes are primarily used to create all kinds of visual elements. They work like any
other object, except that they are created in Motion, and are stored within your project
file. A single shape can be used as a background or colored graphic in a composition,
or you can use a group of shapes to create lines and fills for more complex illustrations.
Each illustration below is composed of shapes created within Motion.
Masks, on the other hand, are used to create regions of transparency in other objects.
While shapes work as objects by themselves, masks must be assigned to an object to
have an effect. For example, if you have a picture in which you want to isolate the
foreground subject, you can create a mask to cut out the background.
Shapes and masks can be animated using behaviors and keyframes, like other objects.
However, you can also animate the control points used to create each shape or mask in
your project. This allows you to animate the actual form of each shape, in addition to
the shape’s basic position, rotation, and scale parameters.
Shape and Mask Drawing Tools
Shapes and masks are both made with splines, and they’re created and edited using
similar tools. This section covers the two spline drawing methods that are available in
Motion—Bezier splines and B-Splines. You can use Bezier shapes and B-Spline shapes
interchangeably for any task.
Object Mask Masked object
01112.book Page 820 Sunday, March 13, 2005 10:36 PM