mathutils py api:

  Vector.angle_signed(other)
  for 2D vectors to get the clockwise angle between them.

  in BLI math its called - angle_signed_v2v2()

shorthand for...

  atan2f((v1[1] * v2[0]) - (v1[0] * v2[1]), dot_v2v2(v1, v2))

also corrects compile error in last commit.

1 files changed, 6 insertions, 0 deletions

diff --git a/source/blender/blenlib/intern/math_vector.c b/source/blender/blenlib/intern/math_vector.c
index 01ba62bc741..39e1a9b31f0 100644
--- a/source/blender/blenlib/intern/math_vector.c
+++ b/source/blender/blenlib/intern/math_vector.c
@@ -174,6 +174,12 @@ float angle_v2v2(const float v1[2], const float v2[2])
 	return angle_normalized_v2v2(vec1, vec2);
 }
 
+float angle_signed_v2v2(const float v1[2], const float v2[2])
+{
+	const float perp_dot = (v1[1] * v2[0]) - (v1[0] * v2[1]);
+	return atan2f(perp_dot, dot_v2v2(v1, v2));
+}
+
 float angle_normalized_v3v3(const float v1[3], const float v2[3])
 {
 	/* this is the same as acos(dot_v3v3(v1, v2)), but more accurate */