Cleanup: comments, redundant normalize

1 files changed, 9 insertions, 6 deletions

diff --git a/source/blender/blenkernel/intern/armature.c b/source/blender/blenkernel/intern/armature.c
index 7d10bce60ef..a694a335069 100644
--- a/source/blender/blenkernel/intern/armature.c
+++ b/source/blender/blenkernel/intern/armature.c
@@ -281,6 +281,11 @@ static void armature_transform_recurse(ListBase *bonebase,
 {
   for (Bone *bone = bonebase->first; bone; bone = bone->next) {
 
+    /* Store the initial bone roll in a matrix, this is needed even for child bones
+     * so any change in head/tail doesn't cause the roll to change.
+     *
+     * Logic here is different to edit-mode because
+     * this is calculated in relative to the parent. */
     float roll_mat3_pre[3][3];
     {
       float delta[3];
@@ -290,6 +295,7 @@ static void armature_transform_recurse(ListBase *bonebase,
         mul_m3_m3m3(roll_mat3_pre, mat3, roll_mat3_pre);
       }
     }
+    /* Optional, use this for predictable results since the roll is re-calculated below anyway. */
     bone->roll = 0.0f;
 
     mul_m4_v3(mat, bone->arm_head);
@@ -308,17 +314,14 @@ static void armature_transform_recurse(ListBase *bonebase,
       copy_v3_v3(bone->tail, bone->arm_tail);
     }
 
+    /* Now the head/tail have been updated, set the roll back, matching 'roll_mat3_pre'. */
     {
-      float roll_mat3_post[3][3];
-      float delta_mat3[3][3];
+      float roll_mat3_post[3][3], delta_mat3[3][3];
       float delta[3];
       sub_v3_v3v3(delta, bone->tail, bone->head);
-      vec_roll_to_mat3(delta, bone->roll, roll_mat3_post);
-      normalize_v3(delta);
-
+      vec_roll_to_mat3(delta, 0.0f, roll_mat3_post);
       invert_m3(roll_mat3_post);
       mul_m3_m3m3(delta_mat3, roll_mat3_post, roll_mat3_pre);
-
       bone->roll = atan2f(delta_mat3[2][0], delta_mat3[2][2]);
     }