manual/editors/graph_editor/fcurves/editing.rst

@@ -500,3 +500,35 @@ Filter Width
 .. figure:: /images/editors_graph-editor_gaussian_smooth.jpg
 
    F-Curve after applying the Gaussian Smooth with the original curve overlayed.
+
+Butterworth Smooth
+------------------
+
+.. reference::
+
+   :Menu:      :menuselection:`Key --> Smooth --> Butterworth Smooth`
+
+Smooth the selected keyframes using a Butterworth filter. This filter is ideal for
+smoothing large amounts of data because it preserves the peaks of the animation.
+The downside is that it can introduce a ripple effect when the key values change rapidly.
+
+Frequency Cutoff
+   The lower the value the smoother the curve. There is an implicit maximum at which
+   the value no longer changes the curve which is at half the sample rate. The sample
+   rate in this case is the scene frame rate multiplied by the `Samples per Frame` of this operator.
+
+Filter order
+   Higher values mean the frequency cutoff is steeper. 
+
+Samples per Frame
+   Before the filter is applied, the curve is resampled at this interval to avoid errors when there
+   are uneven spaces between frames. If keys are on subframes, e.g. a 60fps file in a 30fps scene,
+   increase this value to 2.
+
+Blend
+   A 0-1 value to blend from original curve to filtered curve.
+
+Blend In/Out
+   The number of frames at the start and end for which to blend between the filtered and unfiltered curve.
+   This can help reducing jumps in the animation at the selection border. At value 1 it only locks the first and
+   last frame of the selection to the original position.