Constraints: BBones Head/Tail Interpolation is now optional

To preserve backwards compat with old rigs, the behaviour to use the BBone
shape when interpolating Head/Tail values will now only be performed when
the "curve" toggle beside the head/tail slider is enabled.

TODO: Make this toggle only show up when the target is actually a bbone

4 files changed, 34 insertions, 40 deletions

diff --git a/release/scripts/startup/bl_ui/properties_constraint.py b/release/scripts/startup/bl_ui/properties_constraint.py
index ef0fc9c7c9f..4ca2f773dcc 100644
--- a/release/scripts/startup/bl_ui/properties_constraint.py
+++ b/release/scripts/startup/bl_ui/properties_constraint.py
@@ -65,9 +65,10 @@ class ConstraintButtonsPanel:
                 layout.prop_search(con, "subtarget", con.target.data, "bones", text="Bone")
 
                 if hasattr(con, "head_tail"):
-                    row = layout.row()
+                    row = layout.row(align=True)
                     row.label(text="Head/Tail:")
                     row.prop(con, "head_tail", text="")
+                    row.prop(con, "use_bbone_shape", text="", icon='IPO_BEZIER')  # XXX icon, and only when bone has segments?
             elif con.target.type in {'MESH', 'LATTICE'}:
                 layout.prop_search(con, "subtarget", con.target, "vertex_groups", text="Vertex Group")
 
diff --git a/source/blender/blenkernel/intern/constraint.c b/source/blender/blenkernel/intern/constraint.c
index e5c662f5caa..a591d536b43 100644
--- a/source/blender/blenkernel/intern/constraint.c
+++ b/source/blender/blenkernel/intern/constraint.c
@@ -535,7 +535,7 @@ static void contarget_get_lattice_mat(Object *ob, const char *substring, float m
 
 /* generic function to get the appropriate matrix for most target cases */
 /* The cases where the target can be object data have not been implemented */
-static void constraint_target_to_mat4(Object *ob, const char *substring, float mat[4][4], short from, short to, float headtail)
+static void constraint_target_to_mat4(Object *ob, const char *substring, float mat[4][4], short from, short to, short flag, float headtail)
 {
 	/*	Case OBJECT */
 	if (substring[0] == '\0') {
@@ -573,7 +573,7 @@ static void constraint_target_to_mat4(Object *ob, const char *substring, float m
 				/* skip length interpolation if set to head */
 				mul_m4_m4m4(mat, ob->obmat, pchan->pose_mat);
 			}
-			else if ((pchan->bone) && (pchan->bone->segments > 1)) {
+			else if ((pchan->bone) && (pchan->bone->segments > 1) && (flag & CONSTRAINT_BBONE_SHAPE)) {
 				/* use point along bbone */
 				Mat4 bbone[MAX_BBONE_SUBDIV];
 				float tempmat[4][4];
@@ -686,7 +686,7 @@ static bConstraintTypeInfo CTI_CONSTRNAME = {
 static void default_get_tarmat(bConstraint *con, bConstraintOb *UNUSED(cob), bConstraintTarget *ct, float UNUSED(ctime))
 {
 	if (VALID_CONS_TARGET(ct))
-		constraint_target_to_mat4(ct->tar, ct->subtarget, ct->matrix, CONSTRAINT_SPACE_WORLD, ct->space, con->headtail);
+		constraint_target_to_mat4(ct->tar, ct->subtarget, ct->matrix, CONSTRAINT_SPACE_WORLD, ct->space, con->flag, con->headtail);
 	else if (ct)
 		unit_m4(ct->matrix);
 }
@@ -1154,7 +1154,7 @@ static void kinematic_get_tarmat(bConstraint *con, bConstraintOb *cob, bConstrai
 	bKinematicConstraint *data = con->data;
 	
 	if (VALID_CONS_TARGET(ct)) 
-		constraint_target_to_mat4(ct->tar, ct->subtarget, ct->matrix, CONSTRAINT_SPACE_WORLD, ct->space, con->headtail);
+		constraint_target_to_mat4(ct->tar, ct->subtarget, ct->matrix, CONSTRAINT_SPACE_WORLD, ct->space, con->flag, con->headtail);
 	else if (ct) {
 		if (data->flag & CONSTRAINT_IK_AUTO) {
 			Object *ob = cob->ob;
@@ -2037,7 +2037,7 @@ static void pycon_get_tarmat(bConstraint *con, bConstraintOb *cob, bConstraintTa
 		/* firstly calculate the matrix the normal way, then let the py-function override
 		 * this matrix if it needs to do so
 		 */
-		constraint_target_to_mat4(ct->tar, ct->subtarget, ct->matrix, CONSTRAINT_SPACE_WORLD, ct->space, con->headtail);
+		constraint_target_to_mat4(ct->tar, ct->subtarget, ct->matrix, CONSTRAINT_SPACE_WORLD, ct->space, con->flag, con->headtail);
 		
 		/* only execute target calculation if allowed */
 #ifdef WITH_PYTHON
@@ -2149,7 +2149,7 @@ static void actcon_get_tarmat(bConstraint *con, bConstraintOb *cob, bConstraintT
 		unit_m4(ct->matrix);
 		
 		/* get the transform matrix of the target */
-		constraint_target_to_mat4(ct->tar, ct->subtarget, tempmat, CONSTRAINT_SPACE_WORLD, ct->space, con->headtail);
+		constraint_target_to_mat4(ct->tar, ct->subtarget, tempmat, CONSTRAINT_SPACE_WORLD, ct->space, con->flag, con->headtail);
 		
 		/* determine where in transform range target is */
 		/* data->type is mapped as follows for backwards compatibility:
diff --git a/source/blender/makesdna/DNA_constraint_types.h b/source/blender/makesdna/DNA_constraint_types.h
index 86991245068..5fcd374b21f 100644
--- a/source/blender/makesdna/DNA_constraint_types.h
+++ b/source/blender/makesdna/DNA_constraint_types.h
@@ -516,7 +516,9 @@ typedef enum eBConstraint_Flags {
 		/* indicates that constraint was added locally (i.e.  didn't come from the proxy-lib) */
 	CONSTRAINT_PROXY_LOCAL = (1<<8),
 		/* indicates that constraint is temporarily disabled (only used in GE) */
-	CONSTRAINT_OFF = (1<<9)
+	CONSTRAINT_OFF = (1<<9),
+		/* use bbone curve shape when calculating headtail values */
+	CONSTRAINT_BBONE_SHAPE = (1<<10),
 } eBConstraint_Flags;
 
 /* bConstraint->ownspace/tarspace */
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");