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, 11 insertions, 0 deletions

diff --git a/source/blender/draw/intern/draw_armature.c b/source/blender/draw/intern/draw_armature.c
index a73bddf880f..5f8a2d00188 100644
--- a/source/blender/draw/intern/draw_armature.c
+++ b/source/blender/draw/intern/draw_armature.c
@@ -940,6 +940,7 @@ static void ebone_spline_preview(EditBone *ebone, float result_array[MAX_BBONE_S
 	BBoneSplineParameters param;
 	EditBone *prev, *next;
 	float imat[4][4], bonemat[4][4];
+	float tmp[3];
 
 	memset(&param, 0, sizeof(param));
 
@@ -979,6 +980,11 @@ static void ebone_spline_preview(EditBone *ebone, float result_array[MAX_BBONE_S
 			if (ebone->bbone_prev_type == BBONE_HANDLE_RELATIVE) {
 				zero_v3(param.prev_h);
 			}
+			else if (ebone->bbone_prev_type == BBONE_HANDLE_TANGENT) {
+				sub_v3_v3v3(tmp, prev->tail, prev->head);
+				sub_v3_v3v3(tmp, ebone->head, tmp);
+				mul_v3_m4v3(param.prev_h, imat, tmp);
+			}
 			else {
 				param.prev_bbone = (prev->segments > 1);
 
@@ -997,6 +1003,11 @@ static void ebone_spline_preview(EditBone *ebone, float result_array[MAX_BBONE_S
 			if (ebone->bbone_next_type == BBONE_HANDLE_RELATIVE) {
 				copy_v3_fl3(param.next_h, 0.0f, param.length, 0.0);
 			}
+			else if (ebone->bbone_next_type == BBONE_HANDLE_TANGENT) {
+				sub_v3_v3v3(tmp, next->tail, next->head);
+				add_v3_v3v3(tmp, ebone->tail, tmp);
+				mul_v3_m4v3(param.next_h, imat, tmp);
+			}
 			else {
 				param.next_bbone = (next->segments > 1);