Adobe After Effects CS4 - Manual (Page 235)

229 USING AFTER EFFECTS CS4
Animation and keyframes
Last updated 12/21/2009
Smooth motion and velocity by removing extra keyframes
Smooth motion paths, value curves, and velocity curves to eliminate bumpiness or excess keyframes using the
Smoother, which adds keyframes or removes unnecessary keyframes.
You can also use the smooth expression method for this purpose, without removing keyframes. (See “ Property
attributes and methods (expression reference) ” on page 677.)
Although you can smooth a curve for any property, the Smoother is most useful when applied to curves that have been
automatically generated by Motion Sketch, where you may have excess keyframes. Applying the Smoother to
keyframes that have been set manually may result in unexpected changes to the curve.
Note: To avoid the need to use the Smoother on a path generated by Motion Sketch, set the Smoothing option in the
Motion Sketch panel before sketching the motion path.
When you apply the Smoother to properties that change spatially (such as Position), you can smooth only the spatial
curve (the curve defined by the motion). When you apply the Smoother to properties that change only in time (such
as Opacity), you can smooth only the value and velocity curves (the curve defined by the value or the velocity).
In addition to adding keyframes or eliminating unnecessary keyframes, the Smoother also applies Bezier interpolation
at each keyframe when smoothing the temporal curve. (See “
Keyframe interpolation methods ” on page 233.)
1 In the Timeline panel, either select all the keyframes for a property to smooth the entire curve, or select at least three
keyframes to smooth only a portion of a curve.
2 Choose Window > Smoother. In the Apply To menu, the Smoother automatically selects Spatial Path or Temporal
Graph, depending on the type of property for which you selected keyframes in step 1.
3 Set a value for Tolerance. The units of Tolerance match the units of the property you are smoothing. New keyframe
values will vary no more than the specified value from the original curve. Higher values produce smoother curves,
but too high a value may not preserve the original shape of the curve.
4 Click Apply and preview the results.
5 If necessary, choose Edit > Undo Smoother to reset the keyframes, adjust the value for Tolerance, and then reapply
the Smoother.
More Help topics
“ Sketch a motion path with Motion Sketch ” on page 226
“ Select keyframes ” on page 215
Add randomness to a property with the Wiggler
You can add randomness to any property as it varies over time by using the Wiggler.
You can also use the wiggle expression method for this purpose. In most cases, it is easier to use the expression than
to use the Wiggler. (See “ Property attributes and methods (expression reference) ” on page 677.)
Depending on the property and the options you specify, the Wiggler adds a certain number of deviations to a property
by adding keyframes and randomizing interpolations coming into or out of existing keyframes. You need at least two
keyframes to use the Wiggler.