Option to normalize rotation matrix

python/damask/_rotation.py

@@ -902,7 +902,8 @@ class Rotation:
         return Rotation(Rotation._om2qu(om))
 
     @staticmethod
-    def from_matrix(R: np.ndarray) -> 'Rotation':
+    def from_matrix(R: np.ndarray,
+                    normalize: bool = False) -> 'Rotation':
         """
         Initialize from rotation matrix.
 
@@ -910,13 +911,17 @@ class Rotation:
         ----------
         R : numpy.ndarray, shape (...,3,3)
             Rotation matrix with det(R) = 1 and R.T ∙ R = I.
+        normalize : bool, optional
+            Rescales rotation matrix to unit determinant. Defaults to False.
 
         Returns
         -------
         new : damask.Rotation
 
         """
-        return Rotation.from_basis(R)
+        return Rotation.from_basis(np.array(R,dtype=float) * (np.linalg.det(R)**(-1./3.))[...,np.newaxis,np.newaxis]
+                                   if normalize else
+                                   R)
 
     @staticmethod
     def from_parallel(a: np.ndarray,

python/tests/test_Rotation.py

@@ -774,9 +774,11 @@ class TestRotation:
                             ).all()
 
 
-    def test_matrix(self,multidim_rotations):
+    @pytest.mark.parametrize('normalize',[True,False])
+    def test_matrix(self,multidim_rotations,normalize):
         m = multidim_rotations
-        o = Rotation.from_matrix(m.as_matrix())
+        o = Rotation.from_matrix(m.as_matrix()*(0.9 if normalize else 1.0),
+                                 normalize=normalize)
         f = Rotation(np.where(np.isclose(m.as_quaternion()[...,0],0.0,atol=atol)[...,np.newaxis],~o,o))
         assert np.logical_or(m.isclose(o,atol=atol),
                              m.isclose(f,atol=atol)