Add a new B-Bone Custom Handle type that uses the handle bone direction.

Both original handle types are based on location, and Absolute uses it
in a weird way: the Start handle uses the head, while End uses the tail.

This makes controlling the shape of the B-Bone via control bone rotation
really non-intuitive, especially if trying to add a single control for
the tangent in the middle of a B-Bone chain.

To remedy this, add a new custom handle type that uses the orientation
of the control bone, while completely ignoring location. It is even
possible to control both ends of one B-Bone with the same handle bone,
resulting in an S shape.

Reviewers: brecht

Differential Revision: https://developer.blender.org/D3769

1 files changed, 23 insertions, 2 deletions

diff --git a/source/blender/blenkernel/intern/armature.c b/source/blender/blenkernel/intern/armature.c
index 91661f0a4e3..198cc526865 100644
--- a/source/blender/blenkernel/intern/armature.c
+++ b/source/blender/blenkernel/intern/armature.c
@@ -468,6 +468,7 @@ void b_bone_spline_setup(bPoseChannel *pchan, int rest, Mat4 result_array[MAX_BB
 	Bone *bone = pchan->bone;
 	BBoneSplineParameters param;
 	float imat[4][4], posemat[4][4];
+	float delta[3];
 
 	memset(&param, 0, sizeof(param));
 
@@ -518,11 +519,21 @@ void b_bone_spline_setup(bPoseChannel *pchan, int rest, Mat4 result_array[MAX_BB
 				done = true;
 			}
 			else {
-				float delta[3];
 				sub_v3_v3v3(delta, prev->pose_head, prev->bone->arm_head);
 				sub_v3_v3v3(h1, pchan->pose_head, delta);
 			}
 		}
+		else if (bone->bbone_prev_type == BBONE_HANDLE_TANGENT) {
+			/* Use bone direction by offsetting so that its tail meets current bone's head */
+			if (rest) {
+				sub_v3_v3v3(delta, prev->bone->arm_tail, prev->bone->arm_head);
+				sub_v3_v3v3(h1, bone->arm_head, delta);
+			}
+			else {
+				sub_v3_v3v3(delta, prev->pose_tail, prev->pose_head);
+				sub_v3_v3v3(h1, pchan->pose_head, delta);
+			}
+		}
 		else {
 			/* Apply special handling for smoothly joining B-Bone chains */
 			param.prev_bbone = (prev->bone->segments > 1);
@@ -556,11 +567,21 @@ void b_bone_spline_setup(bPoseChannel *pchan, int rest, Mat4 result_array[MAX_BB
 				done = true;
 			}
 			else {
-				float delta[3];
 				sub_v3_v3v3(delta, next->pose_head, next->bone->arm_head);
 				add_v3_v3v3(h2, pchan->pose_tail, delta);
 			}
 		}
+		else if (bone->bbone_next_type == BBONE_HANDLE_TANGENT) {
+			/* Use bone direction by offsetting so that its head meets current bone's tail */
+			if (rest) {
+				sub_v3_v3v3(delta, next->bone->arm_tail, next->bone->arm_head);
+				add_v3_v3v3(h2, bone->arm_tail, delta);
+			}
+			else {
+				sub_v3_v3v3(delta, next->pose_tail, next->pose_head);
+				add_v3_v3v3(h2, pchan->pose_tail, delta);
+			}
+		}
 		else {
 			/* Apply special handling for smoothly joining B-Bone chains */
 			param.next_bbone = (next->bone->segments > 1);