To Convert A Mask To A Rotobezier Mask; To Create A Mask From A Motion Path - Adobe AFTER EFFECTS 7.0 Manual

To convert a mask to a RotoBezier mask

You can convert any existing mask to a RotoBezier mask. However, Bezier masks that have adjusted direction lines
change shape when converted to RotoBezier because After Effects calculates RotoBezier segments automatically. You
can convert RotoBezier masks to Bezier without affecting the mask shape.
1 Select a mask in the Layer or Composition panel.
Choose Layer > Mask > RotoBezier.
2
See also
"Changing the shape of a mask" on page 254

To create a mask from a motion path

You can copy position keyframes, anchor point keyframes, or an effect's point position keyframes and paste those
keyframes on a selected mask. This is useful for creating animations that follow the edges of a mask. When you create
masks from motion paths, make sure that you copy keyframes from a single position property only—do not copy the
keyframes of any other property.
The motion path of the spaceship (left) is copied to the background layer (center) and used by the Vegas effect (right).
In the Composition panel, display the motion path from which you want to create the mask.
1
In the Timeline panel, select the successive keyframes along the motion path you want to use as a mask. Click the
2
Position property name to select all the keyframes. Shift-click successive keyframes to select only a few keyframes.
Choose Edit > Copy.
3
In the Timeline panel, select the layer you want to apply the mask to and expand its properties, or open the layer
4
in its Layer panel.
Do one of the following:
5
•
To use the motion path as a new mask, choose Layer > Mask > New Mask.
•
To use the motion path as a replacement for an existing mask, select the mask you want to replace.
In the Timeline panel, expand the Mask property for the mask you want to create or replace, and select the Mask
6
Shape value name.
7 Choose Edit > Paste.
Selecting and copying Position keyframes (left); then pasting them in the selected Mask Shape property (right)
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