Interpolation Methods; No Interpolation; Linear Interpolation - Adobe AFTER EFFECTS 7.0 Manual

ADOBE AFTER EFFECTS 7.0
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User Guide
A B C D E
Timeline keyframe icons in layer bar mode
A. Linear B. Linear in, Hold out C. Auto Bezier D. Continuous Bezier or Bezier E. Linear in, Bezier out
See also
"About changes in speed" on page 224

Interpolation methods

All interpolation methods provided by After Effects are based on the Bezier interpolation method, which provides
direction handles so that you can control the transitions between keyframes. Interpolation methods that don't use
direction handles are constrained versions of Bezier interpolation and are convenient for certain tasks.
To learn more about how different interpolation methods affect temporal properties, experiment by setting up at
least three keyframes with different values for a temporal layer property—such as Opacity— and change the inter-
polation methods as you view the value graph in the Graph Editor view of the Timeline panel.
To learn more about how different interpolation methods affect a motion path, experiment by setting up three
keyframes for a spatial property—such as Position—with different values on a motion path, and change the interpo-
lation methods as you preview the motion in the Composition panel.
In the following descriptions of interpolation methods, the result of each method is described as if you had applied
it to all of the keyframes for a layer property. This is done to clarify the examples. In practice, you can apply any
available interpolation method to any layer property keyframe.

No interpolation

No interpolation is the state in which there are no keyframes for a layer property—when the stopwatch is turned off
and the I-beam icon appears in the Timeline panel under the current-time indicator. In this state, when you set
the value of a layer property, it maintains that value for the layer's duration, unless overridden by an expression. By
default, no interpolation is applied to a layer property. If any keyframes are present for a layer property, some kind
of interpolation is in use. Removing all keyframes from a layer property also removes all interpolation methods from
the layer property.

Linear interpolation

Linear interpolation creates a uniform rate of change between keyframes, which can add a mechanical look to anima-
tions. After Effects interpolates the values between two adjacent keyframes as directly as possible without accounting
for the values of other keyframes.
If you apply Linear interpolation to all keyframes of a temporal layer property, change begins instantly at the first
keyframe and continues to the next keyframe at a constant speed. At the second keyframe, the rate of change switches
immediately to the rate between it and the third keyframe. When the layer reaches the final keyframe value, change
stops instantly. In the value graph, the segment connecting two Linear keyframes appears as a straight line.
If you apply Linear interpolation to all keyframes of a spatial property such as position via the motion path, After
Effects creates a straight line between each keyframe. At each Linear keyframe where a change of direction
occurs, the motion path forms a corner. For example, you might use Linear interpolation on the position keyframes
of the motion path to create the path of a pinball.