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, 8 insertions, 1 deletions

diff --git a/source/blender/makesdna/DNA_curve_types.h b/source/blender/makesdna/DNA_curve_types.h
index a25c00915d2..2207b0ec0b1 100644
--- a/source/blender/makesdna/DNA_curve_types.h
+++ b/source/blender/makesdna/DNA_curve_types.h
@@ -124,7 +124,8 @@ typedef struct BezTriple {
 	float back;					/* BEZT_IPO_BACK */
 	float amplitude, period;	/* BEZT_IPO_ELASTIC */
 
-	char  pad[4];
+	char f5;					/* f5: used for auto handle to distinguish between normal handle and exception (extrema) */
+	char  pad[3];
 } BezTriple;
 
 /* note; alfa location in struct is abused by Key system */
@@ -395,6 +396,12 @@ typedef enum eBezTriple_Handle {
 	HD_ALIGN_DOUBLESIDE = 5,  /* align handles, displayed both of them. used for masks */
 } eBezTriple_Handle;
 
+/* f5 (beztriple) */
+typedef enum eBezTriple_Auto_Type {
+	HD_AUTOTYPE_NORMAL = 0,
+	HD_AUTOTYPE_SPECIAL = 1
+} eBezTriple_Auto_Type;
+
 /* interpolation modes (used only for BezTriple->ipo) */
 typedef enum eBezTriple_Interpolation {
 	/* traditional interpolation */