User Guide

CHAPTER 6
202
Fine-tuning Animation
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 ( ) displays in the Timeline window
under the current-time marker. 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, adding a rhythmic
or mechanical look to animations. After Effects interpolates the values to the next keyframe
as directly as possible without accounting for the values of other keyframes.
If you apply Linear temporal interpolation to all keyframes of a 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 graph segment connecting two Linear keyframes appears as a straight line.
If you apply Linear spatial interpolation to all keyframes of a 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
spatial interpolation to create the path of a pinball. The speed of motion along the path is
controlled by the temporal interpolation applied at each keyframe.
Auto Bezier interpolation
Auto Bezier interpolation creates a smooth rate of change through a keyframe. You might
use Auto Bezier spatial interpolation to create the path of a car turning on a curving road.
As you change an Auto Bezier keyframe value, the positions of Auto Bezier direction
handles change automatically to maintain a smooth transition between keyframes. The
automatic adjustments change the shape of the Value graph or motion path segments on
either side of the keyframe. If the previous and next keyframes also use Auto Bezier inter-
polation, the shape of the segments on the far side of the previous or next keyframes also
changes. If you adjust an Auto Bezier direction handle manually, you convert it to a
Continuous Bezier keyframe.
UG.book Page 202 Wednesday, February 21, 2001 12:05 PM