Adobe After Effects CS3 - Manual (Page 212)

AFTER EFFECTS CS3
User Guide
207
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.
Continuous Bezier interpolation
Like Auto Bezier interpolation, Continuous Bezier interpolation creates a smooth rate of change through a keyframe.
However, you set the positions of Continuous Bezier direction handles manually. Adjustments you make change the
shape of the value graph or motion path segments on either side of the keyframe.
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 a layer’s Position
property 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.