Adobe AFTER EFFECTS 5.5 Help Manual page 113

Adobe After Effects Help
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Understanding parent layers
To assign one layer's transformations to the transformations of another layer, use
parenting. Parenting can affect all transform properties except opacity. Assign parent
layers in the Parent column in the Timeline window. A layer can have only one parent, but
a layer can be a parent to any number of 2D or 3D layers within the same composition. You
cannot animate the act of assigning and removing the parent designation. Parenting
layers is useful for creating complex animations such as linking the movements of a mario-
nette or depicting the orbits of planets in the solar system.
Dragging the pick whip to designate the car layer as the parent
to the cloud layer
Once a layer is made a parent to another layer, the other layer is called the child layer.
Creating a parenting relationship between layers synchronizes the changes in the parent
layer with the corresponding transformation values of the child layers. For example, if a
parent layer moves 5 pixels to the right of its starting position, then the child layer will also
move 5 pixels to the right of its position. You can animate child layers independent of their
parent layers. You can also parent using null objects, which are hidden layers. See "Using
null objects" on page 114 for information on null objects.
When you assign a parent, the child layer's properties become relative to the parent layer
instead of to the composition. By default, After Effects adjusts the keyframe values of the
child layer so that its properties appear to remain relative to the composition and, thereby,
there is no visible alteration to the layer itself. However, you can choose to have the child
layer jump, or visibly alter its properties relative to the parent layer. For example, consider
two layers in a composition, where one of the layer's position property has been changed
and the other has not. If you assign the unchanged layer as the child of the changed layer
and do not choose the jump option, then the child layer will not move. If you do choose
the jump option, then the child layer's position shifts so that its position is now relative to
the parent layer.
Alternately, when you remove a parent from a child layer, you can choose to have the child
layer jump to show that its transform properties are now relative to the composition.
Jumping a layer is useful to depict a change in focus for a particular layer or layers'
animation. For example, you could animate one child layer to encircle a parent layer, then
jump the child to another layer which may be positioned away from the first parent layer.
The child layer can then encircle the new parent at a position relative to the new parent.
To show or hide the Parent column:
Choose Panels > Parent from the Timeline window menu.
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Animating Layers
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