Patch #7767: Constraint Subtargets can now target anywhere on a bone, not just the head or tail

Patch by: Roland Hess (harkyman)

For example, a constraint can be sub-targeted at the 50% (or 31.2% or 85% etc.) point of its target bone, giving you enormous rigging flexibility and removing the need for complex contraptions to do such things as:

- A bone whose base slides only between to points on a rig (CopyLoc with a variable, animated subtarget point)
- Bones that attach to multiple points along another bone (CopyLocs, each with a different head/tail percentage)
- Bones that need to stretch to a point midway between specific spots on two other bones (old way: too crazy to mention; new way: stretch bone between points on end bones, then another stretch to the midpoint of the first stretch)

It is only used for the constraint types for which it is relevant: CopyLoc, TrackTo, StretchTo and MinMax, TrackTo, and Floor.

Notes:
- This is accessed by the Head/Tail number-slider. 
- This value can be animated per constraint
- The old "Copy Bone Tail" option for the CopyLoc constraint has been automatically converted to 1.0 Head/Bone values for the affected constraints
- In the code, this value is in the bConstraint struct, so it is available for all constraints, even though only a few implement it.

1 files changed, 6 insertions, 1 deletions

diff --git a/source/blender/makesdna/DNA_constraint_types.h b/source/blender/makesdna/DNA_constraint_types.h
index 431ef56e1c4..bf512c3faf8 100644
--- a/source/blender/makesdna/DNA_constraint_types.h
+++ b/source/blender/makesdna/DNA_constraint_types.h
@@ -64,6 +64,8 @@ typedef struct bConstraint {
 	char		name[30];	/*	Constraint name */
 	
 	float		enforce;	/* 	Amount of influence exherted by constraint (0.0-1.0) */
+	float		headtail;	/*	Point along subtarget bone where the actual target is. 0=head (default for all), 1=tail*/
+	int			pad;
 } bConstraint;
 
 
@@ -116,7 +118,7 @@ typedef struct bPythonConstraint {
 	char subtarget[32];		/* subtarger from previous implentation (version-patch sets this to "" on file-load) */
 } bPythonConstraint;
 
-/* Single-target subobject constraints ---------------------  */
+
 /* Inverse-Kinematics (IK) constraint */
 typedef struct bKinematicConstraint {
 	Object		*tar;
@@ -134,6 +136,8 @@ typedef struct bKinematicConstraint {
 	float		grabtarget[3];	/* for target-less IK */
 } bKinematicConstraint;
 
+
+/* Single-target subobject constraints ---------------------  */
 /* Track To Constraint */
 typedef struct bTrackToConstraint {
 	Object		*tar;
@@ -386,6 +390,7 @@ typedef enum B_CONSTRAINTCHANNEL_FLAG {
 #define LOCLIKE_X			0x01
 #define LOCLIKE_Y			0x02
 #define LOCLIKE_Z			0x04
+	/* LOCLIKE_TIP is a depreceated option... use headtail=1.0f instead */
 #define LOCLIKE_TIP			0x08
 #define LOCLIKE_X_INVERT	0x10
 #define LOCLIKE_Y_INVERT	0x20