Blender Git Loki

Bugfix [#26222] Alt-O (smooth) in Graph editor destroys fcurve handle
type and data

Recoded Keyframe Smoothing operator to work better for continuous
curves (i.e. ones with monotonically increasing slopes in sections) as
opposed to hypothetically jagged ones.

The old method assumed that handles should be flat as otherwise, you'd
often get unsmooth curves just because you went and tilted some of the
handles for local extrema, causing some unkeyframed overshoots, which
also leads to changes in timing, which in turn often means unsmooth
motion. Hence, the code took advantage of this to do things with less
extra data.

However, now we have a proper "flatten handles" tool (under snap ->
horizontal) so this functionality is not needed in the general case
where it will lead to stair-stepping artifacts.