Adobe AFTER EFFECTS CS3 PROFESSIONAL User Manual page 214

AFTER EFFECTS CS3 208
User Guide
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.
If you apply Bezier interpolation to all keyframes of a layer property, After Effects creates a smooth transition
between keyframes. The initial position of the direction handles is calculated using the same method used in Auto
Bezier interpolation. After Effects maintains existing direction handle positions as you change a Bezier keyframe
value.
Unlike other interpolation methods, Bezier interpolation lets you create any combination of curves and straight lines
along the motion path. Because the two Bezier direction handles operate independently, a curving motion path can
suddenly turn into a sharp corner at a Bezier keyframe. Bezier spatial interpolation is ideal for drawing a motion
path that follows a complex shape, such as a map route or the outline of a logo.
Existing direction handle positions persist as you move a motion-path keyframe. 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 automati-
cally 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 interpolation, 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 .
Auto Bezier is the default spatial interpolation.