5

One imprecise rule of thumb is to move to the frame that’s halfway between any two
keyframed mask shapes and make new adjustments. Continue keyframing shape changes
at the halfway point between every two keyframes until the mask accurately follows the
motion of the subject. For irregularly shaped objects or objects with complex motion,
don’t be surprised if you need to add a large number of keyframes. Nobody ever said
that rotoscoping was fast!
Every time you move the playhead to a new frame and make a change to the mask’s
shape, a keyframe is 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 keyframe.
Shape Animation
parameter keyframes
Shape Animation
parameter
Note: You can also transform masks as you would any other layer. If you move, rotate,
scale, 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
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. For more information on keyframing in general,
see Keyframes and Curves.
1211Chapter 20 Using Shapes, Masks, and Paint Strokes