Apple Motion 3 - Manual (Page 1104)

1104 Chapter 12 Using Shapes and Masks
Every time you move the playhead to a new frame and make a change to the mask’s
shape, a keyframe is automatically created in that shape’s Shape Animation parameter.
If you move the playhead directly on top of a previously existing keyframe, you change
the mask’s shape at that point without creating a new keyframe.
Note: You can also transform and shear masks as you would any other layer. If you
move, rotate, scale, shear, or change the anchor point for a mask while animation
recording is enabled, you add keyframes to additional channels in the Keyframe Editor.
6 When you’ve finished animating the mask, disable Record (press A).
You can also create, delete, and edit the timing of a mask’s Shape Animation keyframes
directly in the Keyframe Editor. For simplicity, each change you make to a mask is
recorded as a single keyframe, no matter how many control points you edited. The
Shape Animation parameter only allows keyframes set to Constant—you cannot use
any other form of keyframe interpolation.
The process used to animate both masks and shapes is identical. To see an example of
shape animation, see “
Animating Shapes ” on page 1063. For more information on
keyframing in general, see “ Keyframes and Curves ” on page 503.
Applying Image Masks to a Layer
Another way you can create transparency in a layer is by using image masks. An image
mask creates transparency in another layer by deriving an alpha channel from another
layer, such as a shape, text, movie, or still image.
Note: You can use masks and image masks together.
Text layer Image layers Layers masked by text layer