Animation sources are signals that vary over time, just like audio signals. To filter these audio signals, you use an audio equalizer. It lets you change the gain/level of different frequency bands (bass to treble) that exist in the signal. Changing the level of a given frequency band results in a change in the audio signal you hear.
An animation equalizer basically does the same thing: not considering the artistic/emotional aspect, animation is nothing more than a time-varying signal, just like an audio signal. These animation signals can be filtered (“broken down”) to isolate their bands of frequencies.
The low frequencies (like the bass in audio) correspond to slow variations of the signal, gathering the overall animation. Those low variations convey a lot of the signal energy—without them, the result is lifeless (imagine music without any bass!). The high frequencies (like the treble in audio) correspond to fast variations of the signal, gathering subtle details and noise. These frequencies are important to give character to animation but don’t usually convey a lot of the signal’s overall energy.
You can control each frequency’s gain (weight) individually, thereby changing the animation. For example, you can alter the frequency of a leg’s motion to exaggerate certain movements in a walk cycle or add just a little more “oomph” to a punch. Normally you’d have to edit the function curves to tweak the animation but when you equalize the action clip, you can adjust the frequency slider that corresponds to the action. This also makes it easy to copy a walk cycle, for example, to many characters in a scene and adjust their frequencies to give them each a different kind of walk.
To equalize an action
1. Select one or more action clips you want to break down into frequencies.
If you equalize multiple clips, one compound clip is created, spanning the same time interval as the original clips.
2. Choose the Clip > Equalize command on the mixer’s command bar and wait for it to process the clip.
A new compound clip is created on a new track directly below (over the same number of frames) the original clip. The compound clip contains the subclips that represent each frequency. The number of frequencies created depends on your animation. For example, a simple action without much variation may have only 3 to 5 frequency bands.
The original clip is muted so that its action doesn’t interfere with the new equalized compound clip.
3. In the Motion Equalizer property editor that opens, you can modify the Gain value for each frequency. Each Gain slider corresponds to each frequency “subclip” in the compound clip: the higher the number, the higher the frequency. The Gain 0 slider affects all frequencies in the clip.
The sliders are all set to 1 which means that every frequency they represent is “added” together give you the original fcurve.
When you change a frequency, you are not changing a particular element (such as rotation or scaling) of the animation—you are changing a level of the overall animation. (You can also change the frequency using the weight sliders at the end of each subclip’s track—see step 5).
If you close the Equalizer property editor, you can open it again by clicking the icon created for it under the model (the same as a custom parameter set icon). As well, you have access to all the Gain parameters within this set.
4. You can open or collapse the equalized compound clip as you would any compound clip. To open it, double-click it: all the subclips appear on separate tracks. To collapse it again, double-click in an empty area of the track or choose Clip > Collapse Compound.
5. You can then modify the gain of each frequency by using the weight sliders at the right end of each clip’s track, just as you would when you’re mixing the weights of clips.
You can also key these weights. For more information on this, see Mixing and Weighting Clips.
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