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.

6 files changed, 92 insertions, 25 deletions

diff --git a/source/blender/blenlib/BLI_math_vector.h b/source/blender/blenlib/BLI_math_vector.h
index 1a24acfe1a5..b8b53f1ba7c 100644
--- a/source/blender/blenlib/BLI_math_vector.h
+++ b/source/blender/blenlib/BLI_math_vector.h
@@ -176,6 +176,7 @@ MINLINE float line_point_side_v2(const float l1[2], const float l2[2], const flo
 /* - angle_normalized_* is faster equivalent if vectors are normalized       */
 
 float angle_v2v2(const float a[2], const float b[2]);
+float angle_signed_v2v2(const float v1[2], const float v2[2]);
 float angle_v2v2v2(const float a[2], const float b[2], const float c[2]);
 float angle_normalized_v2v2(const float a[2], const float b[2]);
 float angle_v3v3(const float a[3], const float b[3]);
diff --git a/source/blender/blenlib/intern/math_geom.c b/source/blender/blenlib/intern/math_geom.c
index f491ea25075..84bc397a7f8 100644
--- a/source/blender/blenlib/intern/math_geom.c
+++ b/source/blender/blenlib/intern/math_geom.c
@@ -1726,31 +1726,29 @@ static float tri_signed_area(const float v1[3], const float v2[3], const float v
 	return 0.5f*((v1[i]-v2[i])*(v2[j]-v3[j]) + (v1[j]-v2[j])*(v3[i]-v2[i]));
 }
 
+/* return 1 when degenerate */
 static int barycentric_weights(const float v1[3], const float v2[3], const float v3[3], const float co[3], const float n[3], float w[3])
 {
-	float a1, a2, a3, asum;
+	float wtot;
 	int i, j;
 
 	axis_dominant_v3(&i, &j, n);
 
-	a1= tri_signed_area(v2, v3, co, i, j);
-	a2= tri_signed_area(v3, v1, co, i, j);
-	a3= tri_signed_area(v1, v2, co, i, j);
+	w[0] = tri_signed_area(v2, v3, co, i, j);
+	w[1] = tri_signed_area(v3, v1, co, i, j);
+	w[2] = tri_signed_area(v1, v2, co, i, j);
 
-	asum= a1 + a2 + a3;
+	wtot = w[0] + w[1] + w[2];
 
-	if (fabsf(asum) < FLT_EPSILON) {
+	if (fabsf(wtot) > FLT_EPSILON) {
+		mul_v3_fl(w, 1.0f / wtot);
+		return 0;
+	}
+	else {
 		/* zero area triangle */
-		w[0]= w[1]= w[2]= 1.0f/3.0f;
+		copy_v3_fl(w, 1.0f / 3.0f);
 		return 1;
 	}
-
-	asum= 1.0f/asum;
-	w[0]= a1*asum;
-	w[1]= a2*asum;
-	w[2]= a3*asum;
-
-	return 0;
 }
 
 void interp_weights_face_v3(float w[4], const float v1[3], const float v2[3], const float v3[3], const float v4[3], const float co[3])
@@ -1809,22 +1807,19 @@ void interp_weights_face_v3(float w[4], const float v1[3], const float v2[3], co
  * note: using area_tri_signed_v2 means locations outside the triangle are correctly weighted */
 void barycentric_weights_v2(const float v1[2], const float v2[2], const float v3[2], const float co[2], float w[3])
 {
-	float wtot_inv, wtot;
+	float wtot;
 
 	w[0] = area_tri_signed_v2(v2, v3, co);
 	w[1] = area_tri_signed_v2(v3, v1, co);
 	w[2] = area_tri_signed_v2(v1, v2, co);
-	wtot = w[0]+w[1]+w[2];
+	wtot = w[0] + w[1] + w[2];
 
 	if (wtot != 0.0f) {
-		wtot_inv = 1.0f/wtot;
-
-		w[0] = w[0]*wtot_inv;
-		w[1] = w[1]*wtot_inv;
-		w[2] = w[2]*wtot_inv;
+		mul_v3_fl(w, 1.0f / wtot);
+	}
+	else { /* dummy values for zero area face */
+		copy_v3_fl(w, 1.0f / 3.0f);
 	}
-	else /* dummy values for zero area face */
-		w[0] = w[1] = w[2] = 1.0f/3.0f;
 }
 
 /* given 2 triangles in 3D space, and a point in relation to the first triangle.
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 */
diff --git a/source/blender/blenlib/intern/math_vector_inline.c b/source/blender/blenlib/intern/math_vector_inline.c
index 6414245fb3e..96587da9784 100644
--- a/source/blender/blenlib/intern/math_vector_inline.c
+++ b/source/blender/blenlib/intern/math_vector_inline.c
@@ -625,6 +625,12 @@ MINLINE void normal_float_to_short_v3(short out[3], const float in[3])
 
 /********************************* Comparison ********************************/
 
+
+MINLINE int is_zero_v2(const float v[3])
+{
+	return (v[0] == 0 && v[1] == 0);
+}
+
 MINLINE int is_zero_v3(const float v[3])
 {
 	return (v[0] == 0 && v[1] == 0 && v[2] == 0);
diff --git a/source/blender/python/bmesh/bmesh_py_select.c b/source/blender/python/bmesh/bmesh_py_select.c
index a9fb5b2b018..37beb43eeb5 100644
--- a/source/blender/python/bmesh/bmesh_py_select.c
+++ b/source/blender/python/bmesh/bmesh_py_select.c
@@ -122,7 +122,7 @@ static PyObject *bpy_bmeditselseq_add(BPy_BMEditSelSeq *self, BPy_BMElem *value)
 		return NULL;
 	}
 
-	BM_select_history_store(self->bm, value->ele)
+	BM_select_history_store(self->bm, value->ele);
 
 	Py_RETURN_NONE;
 }
diff --git a/source/blender/python/mathutils/mathutils_Vector.c b/source/blender/python/mathutils/mathutils_Vector.c
index 6a7ace9c2a4..3434aadced5 100644
--- a/source/blender/python/mathutils/mathutils_Vector.c
+++ b/source/blender/python/mathutils/mathutils_Vector.c
@@ -920,7 +920,7 @@ PyDoc_STRVAR(Vector_angle_doc,
 "   :return: angle in radians or fallback when given\n"
 "   :rtype: float\n"
 "\n"
-"   .. note:: Zero length vectors raise an :exc:`AttributeError`.\n"
+"   .. note:: Zero length vectors raise an :exc:`ValueError`.\n"
 );
 static PyObject *Vector_angle(VectorObject *self, PyObject *args)
 {
@@ -971,6 +971,64 @@ static PyObject *Vector_angle(VectorObject *self, PyObject *args)
 	return PyFloat_FromDouble(saacos(dot / (sqrt(dot_self) * sqrt(dot_other))));
 }
 
+PyDoc_STRVAR(Vector_angle_signed_doc,
+".. function:: angle_signed(other, fallback)\n"
+"\n"
+"   Return the signed angle between two 2D vectors (clockwise is positive).\n"
+"\n"
+"   :arg other: another vector to compare the angle with\n"
+"   :type other: :class:`Vector`\n"
+"   :arg fallback: return this value when the angle cant be calculated\n"
+"      (zero length vector)\n"
+"   :type fallback: any\n"
+"   :return: angle in radians or fallback when given\n"
+"   :rtype: float\n"
+"\n"
+"   .. note:: Zero length vectors raise an :exc:`ValueError`.\n"
+);
+static PyObject *Vector_angle_signed(VectorObject *self, PyObject *args)
+{
+	float tvec[2];
+
+	PyObject *value;
+	PyObject *fallback = NULL;
+
+	if (!PyArg_ParseTuple(args, "O|O:angle_signed", &value, &fallback))
+		return NULL;
+
+	if (BaseMath_ReadCallback(self) == -1)
+		return NULL;
+
+	/* don't use clamped size, rule of thumb is vector sizes must match,
+	 * even though n this case 'w' is ignored */
+	if (mathutils_array_parse(tvec, 2, 2, value, "Vector.angle_signed(other), invalid 'other' arg") == -1)
+		return NULL;
+
+	if (self->size != 2) {
+		PyErr_SetString(PyExc_ValueError,
+		                "Vector must be 2D");
+		return NULL;
+	}
+
+	if (is_zero_v2(self->vec) || is_zero_v2(tvec)) {
+		/* avoid exception */
+		if (fallback) {
+			Py_INCREF(fallback);
+			return fallback;
+		}
+		else {
+			PyErr_SetString(PyExc_ValueError,
+			                "Vector.angle_signed(other): "
+			                "zero length vectors have no valid angle");
+			return NULL;
+		}
+	}
+
+
+	return PyFloat_FromDouble(angle_signed_v2v2(self->vec, tvec));
+}
+
+
 PyDoc_STRVAR(Vector_rotation_difference_doc,
 ".. function:: rotation_difference(other)\n"
 "\n"
@@ -2705,6 +2763,7 @@ static struct PyMethodDef Vector_methods[] = {
 	{"cross", (PyCFunction) Vector_cross, METH_O, Vector_cross_doc},
 	{"dot", (PyCFunction) Vector_dot, METH_O, Vector_dot_doc},
 	{"angle", (PyCFunction) Vector_angle, METH_VARARGS, Vector_angle_doc},
+	{"angle_signed", (PyCFunction) Vector_angle_signed, METH_VARARGS, Vector_angle_signed_doc},
 	{"rotation_difference", (PyCFunction) Vector_rotation_difference, METH_O, Vector_rotation_difference_doc},
 	{"project", (PyCFunction) Vector_project, METH_O, Vector_project_doc},
 	{"lerp", (PyCFunction) Vector_lerp, METH_VARARGS, Vector_lerp_doc},