Adobe After Effects CS3 User Manual

Page 211

AFTER EFFECTS CS3

User Guide

206

All interpolation methods used 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 interpo-
lation methods as you view the value graph in Graph Editor mode in 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.

Note: To change interpolation methods, right-click a keyframe, select Keyframe Interpolation from the menu that
appears, and then select an option from the Temporal Interpolation drop-down menu.

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 keyframe.

“Shortcuts for keyframes” on page 650

“Shortcuts for showing properties in the Timeline panel” on page 647

“Work with the Graph Editor” on page 184

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.

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 keyframes with Linear interpolation appears as a
straight line.

Bezier interpolation

Bezier interpolation provides the most precise control because you manually adjust the shape of the value graph or
motion path segments on either side of the keyframe. Unlike Auto Bezier or Continuous Bezier, the two direction
handles on a Bezier keyframe operate independently in both the value graph and motion path.