Adobe After Effects CS4 - Manual (Page 241)

235 USING AFTER EFFECTS CS4
Animation and keyframes
Last updated 12/21/2009
If you apply Continuous Bezier interpolation to all keyframes of a property, After Effects adjusts the values at each
keyframe to create smooth transitions. After Effects maintains these smooth transitions as you move a Continuous
Bezier keyframe
on either the motion path or the value graph.
Hold interpolation
Hold interpolation is available only as a temporal interpolation method. Use it to change the value of a layer property
over time, but without a gradual transition. This method is useful for strobe effects, or when you want layers to appear
or disappear suddenly.
If you apply Hold temporal interpolation to all keyframes of a layer property, the value of the first keyframe holds
steady until the next keyframe, when the values change immediately. In the value graph, the graph segment following
a Hold keyframe
appears as a horizontal straight line.
Even though Hold interpolation is available only as a temporal interpolation method, the keyframes on the motion
path are visible, but they are not connected by layer-position dots. For example, if you animate the Position property
of a layer using Hold interpolation, the layer holds at the position value of the previous keyframe until the current-time
indicator reaches the next keyframe, at which point the layer disappears from the old position and appears at the new
position.
You can easily freeze the current frame for the duration of the layer using the Freeze Frame command. To freeze a
frame, position the current time indicator at the frame you want to freeze. Make sure that the layer is selected and then
choose Layer
> Time > Freeze Frame. Time-remapping is enabled, and a Hold keyframe is placed at the position of the
current time indicator to freeze the frame.
Note: If you previously enabled time-remapping on the layer, any keyframes you created are deleted when you apply the
Freeze Frame command.
You can use Hold interpolation only for outgoing temporal interpolation (for the frames following a keyframe). If you
create a keyframe following a Hold keyframe, the new keyframe uses incoming Hold interpolation.
To apply or remove Hold interpolation as outgoing interpolation for a keyframe, select the keyframe in the Timeline
panel, and choose Animation
> Toggle Hold Keyframe.
Apply and change keyframe interpolation methods
You can apply and change the interpolation method for any keyframe. You can apply changes using the Keyframe
Interpolation dialog box, or you can apply them directly to a keyframe in layer bar mode, in a motion path, or in the
Graph Editor. You can also change the default interpolation After Effects uses for spatial properties.
For information on using Easy Ease controls to automatically ease speed between keyframes, see “ Controlling speed
between keyframes ” on page 237.
More Help topics
“ Select keyframes ” on page 215
“ About animation, keyframes, and expressions ” on page 210
“ Keyframes and the Graph Editor (keyboard shortcuts) ” on page 751
“ Showing properties and groups in the Timeline panel (keyboard shortcuts) ” on page 748