Implement a new automatic handle algorithm to produce smooth F-Curves.

The legacy algorithm only considers two adjacent points when computing
the bezier handles, which cannot produce satisfactory results. Animators
are often forced to manually adjust all curves.

The new approach instead solves a system of equations to trace a cubic spline
with continuous second derivative through the whole segment of auto points,
delimited at ends by keyframes with handles set by other requirements.

This algorithm also adjusts Vector handles that face ordinary bezier keyframes
to achieve zero acceleration at the Vector keyframe, instead of simply pointing
it at the adjacent point.

Original idea and implementation by Benoit Bolsee <benoit.bolsee@online.be>;
code mostly rewritten to improve code clarity and extensibility.

Reviewers: aligorith

Differential Revision: https://developer.blender.org/D2884

1 files changed, 3 insertions, 1 deletions

diff --git a/source/blender/blenkernel/BKE_curve.h b/source/blender/blenkernel/BKE_curve.h
index 30db8f45059..175fa1dad79 100644
--- a/source/blender/blenkernel/BKE_curve.h
+++ b/source/blender/blenkernel/BKE_curve.h
@@ -202,10 +202,12 @@ void BKE_nurb_bpoint_calc_normal(struct Nurb *nu, struct BPoint *bp, float r_nor
 void BKE_nurb_bpoint_calc_plane(struct Nurb *nu, struct BPoint *bp, float r_plane[3]);
 
 void BKE_nurb_handle_calc(struct BezTriple *bezt, struct BezTriple *prev,  struct BezTriple *next,
-                          const bool is_fcurve);
+                          const bool is_fcurve, const char smoothing);
 void BKE_nurb_handle_calc_simple(struct Nurb *nu, struct BezTriple *bezt);
 void BKE_nurb_handle_calc_simple_auto(struct Nurb *nu, struct BezTriple *bezt);
 
+void BKE_nurb_handle_smooth_fcurve(struct BezTriple *bezt, int total, bool cyclic);
+
 void BKE_nurb_handles_calc(struct Nurb *nu);
 void BKE_nurb_handles_autocalc(struct Nurb *nu, int flag);
 void BKE_nurb_bezt_handle_test(struct BezTriple *bezt, const bool use_handle);