Averages all keyframes using intelligent low-pass smoothing. The Butterworth is a frequency filter that works best on curves affected by noise.
Unlike the Smooth filter (see Smooth filter), the Butterworth filter removes noise from data without affecting the FCurve’s minimum or maximum values. In this way, the Butterworth filter avoids the “over-averaging” problems that can happen when filtering motion capture data.
When you select the Butterworth filter in the Filters window, you can set the following parameters:
Lets you establish a limit frequency value, in Hertz (Hz). All frequencies higher than this value are cut. The lower the value, the more frequencies are removed, resulting in a much smoother curve.
Removing too many frequencies changes the shape of the curve.
Lets you specify the sampling rate at which keyframes are added to the filtered curve. The default value is 30.
Snaps all keyframes to the nearest frame (see Keys on Frame filter).