Adobe After Effects - Manual (Page 232)

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Smooth Noise
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.
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.)
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.
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).)
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.
Using the Wiggler, you can more closely simulate natural movement within specified limits. For example, add randomness to an animated butterfly
to produce fluttering. Add it to brightness or opacity to simulate the flicker of an old projector.
1. Select a range of keyframes for the property.
2. Choose Window > Wiggler.
3. For Apply To, select the type of curve you want the Wiggler to change. If you selected keyframes for a property that varies spatially, you can
select Spatial Path to add deviations to the motion, or Temporal Graph to add deviations to the velocity. If you selected keyframes for a
property that does not vary spatially, you can select only Temporal Graph.
4. Select a Noise Type option to specify the type of deviation due to randomly distributed pixel values (noise):
Produces deviations that occur more gradually, without sudden changes.
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