Bendy Bones: Advanced B-Bones for Easier + Simple Rigging

This commit/patch/branch brings a bunch of powerful new options for B-Bones and
for working with B-Bones, making it easier for animators to create their own
rigs, using fewer bones (which also means hopefully lighter + faster rigs ;)
This functionality was first demoed by Daniel at BConf15

Some highlights from this patch include:
* You can now directly control the shape of B-Bones using a series of properties
  instead of being restricted to trying to indirectly control them through the
  neighbouring bones.  See the "Bendy Bones" panel...

* B-Bones can be shaped in EditMode to define a "curved rest pose" for the bone.
  This is useful for things like eyebrows and mouths/eyelids

* You can now make B-Bones use custom bones as their reference bone handles,
  instead of only using the parent/child bones. To do so, enable the
  "Use Custom Reference Handles" toggle. If none are specified, then the BBone will
  only use the Bendy Bone properties.

* Constraints Head/Tail option can now slide along the B-Bone shape, instead of
  just linearly interpolating between the endpoints of the bone.

For more details, see:
* http://aligorith.blogspot.co.nz/2016/05/bendy-bones-dev-update.html
* http://aligorith.blogspot.co.nz/2016/05/an-in-depth-look-at-how-b-bones-work.html



-- Credits --
Original Idea: Daniel M Lara (pepeland)
Original Patch/Research: Jose Molina
Additional Development + Polish: Joshua Leung (aligorith)
Testing/Feedback: Daniel M Lara (pepeland), Juan Pablo Bouza (jpbouza)

4 files changed, 147 insertions, 32 deletions

diff --git a/source/blender/makesrna/intern/rna_armature.c b/source/blender/makesrna/intern/rna_armature.c
index a8ef4664fd7..842e220e8b5 100644
--- a/source/blender/makesrna/intern/rna_armature.c
+++ b/source/blender/makesrna/intern/rna_armature.c
@@ -482,6 +482,82 @@ static void rna_Armature_transform(struct bArmature *arm, float *mat)
 
 #else
 
+/* Settings for curved bbone settings - The posemode values get applied over the top of the editmode ones */
+void rna_def_bone_curved_common(StructRNA *srna, bool is_posebone)
+{
+#define RNA_DEF_CURVEBONE_UPDATE(prop, is_posebone)                                \
+	{                                                                              \
+		if (is_posebone)                                                           \
+			RNA_def_property_update(prop, NC_OBJECT | ND_POSE, "rna_Pose_update"); \
+		else                                                                       \
+			RNA_def_property_update(prop, 0, "rna_Armature_update_data");          \
+	} (void)0;
+	
+	PropertyRNA *prop;
+	
+	/* Roll In/Out */
+	prop = RNA_def_property(srna, "bbone_rollin", PROP_FLOAT, PROP_ANGLE);
+	RNA_def_property_float_sdna(prop, NULL, "roll1");
+	RNA_def_property_range(prop, -M_PI * 2.0f, M_PI * 2.0f);
+	RNA_def_property_ui_text(prop, "Roll In", "Roll offset for the start of the B-Bone, adjusts twist");
+	RNA_DEF_CURVEBONE_UPDATE(prop, is_posebone);
+	
+	prop = RNA_def_property(srna, "bbone_rollout", PROP_FLOAT, PROP_ANGLE);
+	RNA_def_property_float_sdna(prop, NULL, "roll2");
+	RNA_def_property_range(prop, -M_PI * 2.0f, M_PI * 2.0f);
+	RNA_def_property_ui_text(prop, "Roll Out", "Roll offset for the end of the B-Bone, adjusts twist");
+	RNA_DEF_CURVEBONE_UPDATE(prop, is_posebone);
+	
+	if (is_posebone == false) {
+		prop = RNA_def_property(srna, "use_endroll_as_inroll", PROP_BOOLEAN, PROP_NONE);
+		RNA_def_property_ui_text(prop, "Inherit End Roll", "Use Roll Out of parent bone as Roll In of its children");
+		RNA_def_property_boolean_sdna(prop, NULL, "flag", BONE_ADD_PARENT_END_ROLL);
+		RNA_def_property_update(prop, 0, "rna_Armature_update_data");
+	}
+	
+	/* Curve X/Y Offsets */
+	prop = RNA_def_property(srna, "bbone_curveinx", PROP_FLOAT, PROP_NONE);
+	RNA_def_property_float_sdna(prop, NULL, "curveInX");
+	RNA_def_property_range(prop, -5.0f, 5.0f);
+	RNA_def_property_ui_text(prop, "In X", "X-axis handle offset for start of the B-Bone's curve, adjusts curvature");
+	RNA_DEF_CURVEBONE_UPDATE(prop, is_posebone);
+	
+	prop = RNA_def_property(srna, "bbone_curveiny", PROP_FLOAT, PROP_NONE);
+	RNA_def_property_float_sdna(prop, NULL, "curveInY");
+	RNA_def_property_range(prop, -5.0f, 5.0f);
+	RNA_def_property_ui_text(prop, "In Y", "Y-axis handle offset for start of the B-Bone's curve, adjusts curvature");
+	RNA_DEF_CURVEBONE_UPDATE(prop, is_posebone);
+	
+	prop = RNA_def_property(srna, "bbone_curveoutx", PROP_FLOAT, PROP_NONE);
+	RNA_def_property_float_sdna(prop, NULL, "curveOutX");
+	RNA_def_property_range(prop, -5.0f, 5.0f);
+	RNA_def_property_ui_text(prop, "Out X", "X-axis handle offset for end of the B-Bone's curve, adjusts curvature");
+	RNA_DEF_CURVEBONE_UPDATE(prop, is_posebone);
+	
+	prop = RNA_def_property(srna, "bbone_curveouty", PROP_FLOAT, PROP_NONE);
+	RNA_def_property_float_sdna(prop, NULL, "curveOutY");
+	RNA_def_property_range(prop, -5.0f, 5.0f);
+	RNA_def_property_ui_text(prop, "Out Y", "Y-axis handle offset for end of the B-Bone's curve, adjusts curvature");
+	RNA_DEF_CURVEBONE_UPDATE(prop, is_posebone);
+	
+	/* Scale In/Out */
+	prop = RNA_def_property(srna, "bbone_scalein", PROP_FLOAT, PROP_NONE);
+	RNA_def_property_float_sdna(prop, NULL, "scaleIn");
+	RNA_def_property_range(prop, 0.0f, 5.0f);
+	RNA_def_property_float_default(prop, 1.0f);
+	RNA_def_property_ui_text(prop, "Scale In", "Scale factor for start of the B-Bone, adjusts thickness (for tapering effects)");
+	RNA_DEF_CURVEBONE_UPDATE(prop, is_posebone);
+	
+	prop = RNA_def_property(srna, "bbone_scaleout", PROP_FLOAT, PROP_NONE);
+	RNA_def_property_float_sdna(prop, NULL, "scaleOut");
+	RNA_def_property_range(prop, 0.0f, 5.0f);
+	RNA_def_property_float_default(prop, 1.0f);
+	RNA_def_property_ui_text(prop, "Scale Out", "Scale factor for end of the B-Bone, adjusts thickness (for tapering effects)");
+	RNA_DEF_CURVEBONE_UPDATE(prop, is_posebone);
+	
+#undef RNA_DEF_CURVEBONE_UPDATE
+}
+
 static void rna_def_bone_common(StructRNA *srna, int editbone)
 {
 	PropertyRNA *prop;
@@ -653,6 +729,7 @@ static void rna_def_bone(BlenderRNA *brna)
 	RNA_def_property_ui_text(prop, "Children", "Bones which are children of this bone");
 
 	rna_def_bone_common(srna, 0);
+	rna_def_bone_curved_common(srna, 0);
 
 	/* XXX should we define this in PoseChannel wrapping code instead?
 	 *     But PoseChannels directly get some of their flags from here... */
@@ -766,6 +843,7 @@ static void rna_def_edit_bone(BlenderRNA *brna)
 	RNA_def_property_update(prop, 0, "rna_Armature_editbone_transform_update");
 
 	rna_def_bone_common(srna, 1);
+	rna_def_bone_curved_common(srna, 0);
 
 	prop = RNA_def_property(srna, "hide", PROP_BOOLEAN, PROP_NONE);
 	RNA_def_property_boolean_sdna(prop, NULL, "flag", BONE_HIDDEN_A);
diff --git a/source/blender/makesrna/intern/rna_constraint.c b/source/blender/makesrna/intern/rna_constraint.c
index 0b5d0f3d41d..98560bf3452 100644
--- a/source/blender/makesrna/intern/rna_constraint.c
+++ b/source/blender/makesrna/intern/rna_constraint.c
@@ -483,6 +483,21 @@ static EnumPropertyItem constraint_distance_items[] = {
 };
 
 
+static void rna_def_constraint_headtail_common(StructRNA *srna)
+{
+	PropertyRNA *prop;
+	
+	prop = RNA_def_property(srna, "head_tail", PROP_FLOAT, PROP_FACTOR);
+	RNA_def_property_float_sdna(prop, "bConstraint", "headtail");
+	RNA_def_property_ui_text(prop, "Head/Tail", "Target along length of bone: Head=0, Tail=1");
+	RNA_def_property_update(prop, NC_OBJECT | ND_CONSTRAINT, "rna_Constraint_update");
+	
+	prop = RNA_def_property(srna, "use_bbone_shape", PROP_BOOLEAN, PROP_NONE);
+	RNA_def_property_boolean_sdna(prop, "bConstraint", "flag", CONSTRAINT_BBONE_SHAPE);
+	RNA_def_property_ui_text(prop, "Follow B-Bone", "Follow shape of B-Bone segments when calculating Head/Tail position");
+	RNA_def_property_update(prop, NC_OBJECT | ND_CONSTRAINT, "rna_Constraint_update");
+}
+
 static void rna_def_constrainttarget(BlenderRNA *brna)
 {
 	StructRNA *srna;
@@ -787,10 +802,7 @@ static void rna_def_constraint_track_to(BlenderRNA *brna)
 	srna = RNA_def_struct(brna, "TrackToConstraint", "Constraint");
 	RNA_def_struct_ui_text(srna, "Track To Constraint", "Aim the constrained object toward the target");
 
-	prop = RNA_def_property(srna, "head_tail", PROP_FLOAT, PROP_FACTOR);
-	RNA_def_property_float_sdna(prop, "bConstraint", "headtail");
-	RNA_def_property_ui_text(prop, "Head/Tail", "Target along length of bone: Head=0, Tail=1");
-	RNA_def_property_update(prop, NC_OBJECT | ND_CONSTRAINT, "rna_Constraint_update");
+	rna_def_constraint_headtail_common(srna);
 
 	RNA_def_struct_sdna_from(srna, "bTrackToConstraint", "data");
 
@@ -831,10 +843,7 @@ static void rna_def_constraint_locate_like(BlenderRNA *brna)
 	srna = RNA_def_struct(brna, "CopyLocationConstraint", "Constraint");
 	RNA_def_struct_ui_text(srna, "Copy Location Constraint", "Copy the location of the target");
 
-	prop = RNA_def_property(srna, "head_tail", PROP_FLOAT, PROP_FACTOR);
-	RNA_def_property_float_sdna(prop, "bConstraint", "headtail");
-	RNA_def_property_ui_text(prop, "Head/Tail", "Target along length of bone: Head=0, Tail=1");
-	RNA_def_property_update(prop, NC_OBJECT | ND_CONSTRAINT, "rna_Constraint_update");
+	rna_def_constraint_headtail_common(srna);
 
 	RNA_def_struct_sdna_from(srna, "bLocateLikeConstraint", "data");
 
@@ -1022,10 +1031,7 @@ static void rna_def_constraint_transform_like(BlenderRNA *brna)
 	srna = RNA_def_struct(brna, "CopyTransformsConstraint", "Constraint");
 	RNA_def_struct_ui_text(srna, "Copy Transforms Constraint", "Copy all the transforms of the target");
 	
-	prop = RNA_def_property(srna, "head_tail", PROP_FLOAT, PROP_FACTOR);
-	RNA_def_property_float_sdna(prop, "bConstraint", "headtail");
-	RNA_def_property_ui_text(prop, "Head/Tail", "Target along length of bone: Head=0, Tail=1");
-	RNA_def_property_update(prop, NC_OBJECT | ND_CONSTRAINT, "rna_Constraint_update");
+	rna_def_constraint_headtail_common(srna);
 
 	RNA_def_struct_sdna_from(srna, "bTransLikeConstraint", "data");
 
@@ -1200,10 +1206,7 @@ static void rna_def_constraint_locked_track(BlenderRNA *brna)
 	RNA_def_struct_ui_text(srna, "Locked Track Constraint",
 	                       "Point toward the target along the track axis, while locking the other axis");
 	
-	prop = RNA_def_property(srna, "head_tail", PROP_FLOAT, PROP_FACTOR);
-	RNA_def_property_float_sdna(prop, "bConstraint", "headtail");
-	RNA_def_property_ui_text(prop, "Head/Tail", "Target along length of bone: Head=0, Tail=1");
-	RNA_def_property_update(prop, NC_OBJECT | ND_CONSTRAINT, "rna_Constraint_update");
+	rna_def_constraint_headtail_common(srna);
 	
 	RNA_def_struct_sdna_from(srna, "bLockTrackConstraint", "data");
 
@@ -1327,10 +1330,7 @@ static void rna_def_constraint_stretch_to(BlenderRNA *brna)
 	srna = RNA_def_struct(brna, "StretchToConstraint", "Constraint");
 	RNA_def_struct_ui_text(srna, "Stretch To Constraint", "Stretch to meet the target object");
 
-	prop = RNA_def_property(srna, "head_tail", PROP_FLOAT, PROP_FACTOR);
-	RNA_def_property_float_sdna(prop, "bConstraint", "headtail");
-	RNA_def_property_ui_text(prop, "Head/Tail", "Target along length of bone: Head=0, Tail=1");
-	RNA_def_property_update(prop, NC_OBJECT | ND_CONSTRAINT, "rna_Constraint_update");
+	rna_def_constraint_headtail_common(srna);
 
 	RNA_def_struct_sdna_from(srna, "bStretchToConstraint", "data");
 
@@ -2122,10 +2122,7 @@ static void rna_def_constraint_distance_limit(BlenderRNA *brna)
 	srna = RNA_def_struct(brna, "LimitDistanceConstraint", "Constraint");
 	RNA_def_struct_ui_text(srna, "Limit Distance Constraint", "Limit the distance from target object");
 	
-	prop = RNA_def_property(srna, "head_tail", PROP_FLOAT, PROP_FACTOR);
-	RNA_def_property_float_sdna(prop, "bConstraint", "headtail");
-	RNA_def_property_ui_text(prop, "Head/Tail", "Target along length of bone: Head=0, Tail=1");
-	RNA_def_property_update(prop, NC_OBJECT | ND_CONSTRAINT, "rna_Constraint_update");
+	rna_def_constraint_headtail_common(srna);
 	
 	RNA_def_struct_sdna_from(srna, "bDistLimitConstraint", "data");
 
@@ -2236,10 +2233,7 @@ static void rna_def_constraint_damped_track(BlenderRNA *brna)
 	RNA_def_struct_ui_text(srna, "Damped Track Constraint",
 	                       "Point toward target by taking the shortest rotation path");
 	
-	prop = RNA_def_property(srna, "head_tail", PROP_FLOAT, PROP_FACTOR);
-	RNA_def_property_float_sdna(prop, "bConstraint", "headtail");
-	RNA_def_property_ui_text(prop, "Head/Tail", "Target along length of bone: Head=0, Tail=1");
-	RNA_def_property_update(prop, NC_OBJECT | ND_CONSTRAINT, "rna_Constraint_update");
+rna_def_constraint_headtail_common(srna);
 	
 	RNA_def_struct_sdna_from(srna, "bDampTrackConstraint", "data");
 
@@ -2396,10 +2390,7 @@ static void rna_def_constraint_pivot(BlenderRNA *brna)
 	srna = RNA_def_struct(brna, "PivotConstraint", "Constraint");
 	RNA_def_struct_ui_text(srna, "Pivot Constraint", "Rotate around a different point");
 	
-	prop = RNA_def_property(srna, "head_tail", PROP_FLOAT, PROP_FACTOR);
-	RNA_def_property_float_sdna(prop, "bConstraint", "headtail");
-	RNA_def_property_ui_text(prop, "Head/Tail", "Target along length of bone: Head=0, Tail=1");
-	RNA_def_property_update(prop, NC_OBJECT | ND_CONSTRAINT, "rna_Constraint_update");
+	rna_def_constraint_headtail_common(srna);
 	
 	RNA_def_struct_sdna_from(srna, "bPivotConstraint", "data");
 	
diff --git a/source/blender/makesrna/intern/rna_internal.h b/source/blender/makesrna/intern/rna_internal.h
index 703b02f9d18..161e19f581c 100644
--- a/source/blender/makesrna/intern/rna_internal.h
+++ b/source/blender/makesrna/intern/rna_internal.h
@@ -197,6 +197,8 @@ void rna_def_animdata_common(struct StructRNA *srna);
 void rna_def_animviz_common(struct StructRNA *srna);
 void rna_def_motionpath_common(struct StructRNA *srna);
 
+void rna_def_bone_curved_common(struct StructRNA *srna, bool is_posebone);
+
 void rna_def_texmat_common(struct StructRNA *srna, const char *texspace_editable);
 void rna_def_mtex_common(struct BlenderRNA *brna, struct StructRNA *srna, const char *begin, const char *activeget,
                          const char *activeset, const char *activeeditable, const char *structname,
diff --git a/source/blender/makesrna/intern/rna_pose.c b/source/blender/makesrna/intern/rna_pose.c
index 5bbc2b49a0d..fb7d5141a6d 100644
--- a/source/blender/makesrna/intern/rna_pose.c
+++ b/source/blender/makesrna/intern/rna_pose.c
@@ -872,6 +872,50 @@ static void rna_def_pose_channel(BlenderRNA *brna)
 	RNA_def_property_ui_text(prop, "Rotation Mode", "");
 	RNA_def_property_update(prop, NC_OBJECT | ND_POSE, "rna_Pose_update");
 	
+	/* Curved bones settings - Applied on top of restpose values */
+	rna_def_bone_curved_common(srna, true);
+	
+	/* Custom BBone next/prev sources */
+	prop = RNA_def_property(srna, "use_bbone_custom_handles", PROP_BOOLEAN, PROP_NONE);
+	RNA_def_property_boolean_sdna(prop, NULL, "bboneflag", PCHAN_BBONE_CUSTOM_HANDLES);
+	RNA_def_property_ui_text(prop, "Use Custom Handle References", 
+	                         "Use custom reference bones as handles for B-Bones instead of next/previous bones, "
+	                         "leave these blank to use only B-Bone offset properties to control the shape");
+	RNA_def_property_editable_func(prop, "rna_PoseChannel_proxy_editable");
+	RNA_def_property_update(prop, NC_OBJECT | ND_POSE, "rna_Pose_update");
+	
+	prop = RNA_def_property(srna, "bbone_custom_handle_start", PROP_POINTER, PROP_NONE);
+	RNA_def_property_pointer_sdna(prop, NULL, "bbone_prev");
+	RNA_def_property_struct_type(prop, "PoseBone");
+	RNA_def_property_flag(prop, PROP_EDITABLE);
+	RNA_def_property_ui_text(prop, "B-Bone Start Handle",
+	                         "Bone that serves as the start handle for the B-Bone curve");
+	RNA_def_property_editable_func(prop, "rna_PoseChannel_proxy_editable");
+	RNA_def_property_update(prop, NC_OBJECT | ND_POSE, "rna_Pose_update");
+	
+	prop = RNA_def_property(srna, "use_bbone_relative_start_handle", PROP_BOOLEAN, PROP_NONE);
+	RNA_def_property_boolean_sdna(prop, NULL, "bboneflag", PCHAN_BBONE_CUSTOM_START_REL);
+	RNA_def_property_ui_text(prop, "Relative B-Bone Start Handle", 
+	                         "Use treat custom start handle position as a relative value");
+	RNA_def_property_editable_func(prop, "rna_PoseChannel_proxy_editable");
+	RNA_def_property_update(prop, NC_OBJECT | ND_POSE, "rna_Pose_update");
+	
+	prop = RNA_def_property(srna, "bbone_custom_handle_end", PROP_POINTER, PROP_NONE);
+	RNA_def_property_pointer_sdna(prop, NULL, "bbone_next");
+	RNA_def_property_struct_type(prop, "PoseBone");
+	RNA_def_property_flag(prop, PROP_EDITABLE);
+	RNA_def_property_ui_text(prop, "B-Bone End Handle",
+	                         "Bone that serves as the end handle for the B-Bone curve");
+	RNA_def_property_editable_func(prop, "rna_PoseChannel_proxy_editable");
+	RNA_def_property_update(prop, NC_OBJECT | ND_POSE, "rna_Pose_update");
+	
+	prop = RNA_def_property(srna, "use_bbone_relative_end_handle", PROP_BOOLEAN, PROP_NONE);
+	RNA_def_property_boolean_sdna(prop, NULL, "bboneflag", PCHAN_BBONE_CUSTOM_END_REL);
+	RNA_def_property_ui_text(prop, "Relative B-Bone End Handle", 
+	                         "Use treat custom end handle position as a relative value");
+	RNA_def_property_editable_func(prop, "rna_PoseChannel_proxy_editable");
+	RNA_def_property_update(prop, NC_OBJECT | ND_POSE, "rna_Pose_update");
+	
 	/* transform matrices - should be read-only since these are set directly by AnimSys evaluation */
 	prop = RNA_def_property(srna, "matrix_channel", PROP_FLOAT, PROP_MATRIX);
 	RNA_def_property_float_sdna(prop, NULL, "chan_mat");