Using Help | Contents | Index Back - Adobe AFTER EFFECTS 5.5 Help Manual

Adobe After Effects Help
Using Help | Contents
To specify a mask as the target of all new shapes:
In the Layer window, select the mask name from the Target pop-up menu.
To specify no mask as a target for changes:
In the Layer window, select None from the Target pop-up menu.
Animating a mask
You can change all of a layer's Mask property values—Mask Shape, Mask Feather, Mask
Opacity, or Mask Expansion—over time by using keyframes (see "Understanding
keyframes" on page 96).
To animate a mask shape, After Effects designates the topmost control point at the initial
keyframe as the first vertex and "numbers" each successive control point in ascending
order from the first vertex. After Effects then assigns the same numbers to the corre-
sponding control points at all successive keyframes. After Effects interpolates the
movement of each control point from its initial position at one keyframe to the position of
the correspondingly numbered control point at the next keyframe. At any time during an
animation, you can designate another control point as the first vertex; this causes After
Effects to renumber the control points of the shape you assigned a new first vertex, and
the mask animates differently as After Effects now maps the new vertex numbers to the
corresponding "old" vertex numbers still saved at successive keyframes.
To animate a mask property:
1 In the Timeline or Composition window, select the mask that you want to animate.
2 Move the current-time marker to the time where you want to begin the animation.
3 Expand the Mask properties and locate the property that you want to change.
4 Set a value for the mask property. For information on setting a mask value, see the
corresponding section for the value you want to set. For example, for information on
setting Mask Opacity, see "Adjusting the opacity of a mask" on page 157.
5 Set an initial keyframe. For information on setting keyframes, see "Setting keyframes"
on page 98.
6 Move the current-time marker to the time where you want to add the second keyframe.
7 Change the value for the mask property.
Repeat steps 7 and 8 as many times as you want to add more keyframes.
Note: By default, when you add a control point to a mask, the new point appears on the
mask throughout the mask's duration but reshapes the mask only at the time it was
added. When you delete a control point from a mask at a specific point in time, the point is
deleted from the mask throughout the mask's duration. Prevent After Effects from adding
and deleting control points throughout the mask's duration by choosing Edit > Prefer-
ences > General and deselecting Preserve Constant Vertex Count When Editing Masks.
To designate another control point as the first vertex:
1 Create an animated mask shape, as described in the previous procedure.
2 In the Timeline window, move the current time marker to the point where you want to
designate a new first vertex.
Using Help | Contents
| Index
| Index
Working with Masks and Transparency
Back
Back
160
160