Increase consistency in where the Rowland tori are oriented

marxs/design/rowland.py

@@ -479,10 +479,11 @@ def double_rowland_from_channel_distance(d_BF, R, f):
            (r + R) * np.sin(-alpha),
             0]
 
-    orientm = [[-np.cos(alpha), np.sin(alpha), 0],
-               [-np.sin(alpha), -np.cos(alpha), 0],
-               [0., 0., 1]]
-
+    orientm = [
+        [np.cos(-alpha), np.sin(-alpha), 0],
+        [-np.sin(-alpha), np.cos(-alpha), 0],
+        [0.0, 0.0, 1],
+    ]
 
     geometry = {'d_BF': d_BF,
                 'd': d,

marxs/design/tests/test_design.py

@@ -1,5 +1,6 @@
 # Licensed under GPL version 3 - see LICENSE.rst
 import numpy as np
+from numpy.testing import assert_allclose
 from scipy.stats import kstest
 import transforms3d
 import pytest
@@ -496,4 +497,20 @@ def test_offset_double_rowland_channels():
                                             '2m': [0, 2.5, 12.5],
                                             })
     assert geom['pos_opt_ax']['2m'] == pytest.approx([0, 302.5, 12.5, 1. ])
-    assert geom['rowland_1'].geometry['center'] == pytest.approx([7.48596673, 297.12570166, -7.5, 1.])
+    assert geom['rowland_1'].geometry['center'] == pytest.approx([7.48596673, 297.12570166, -7.5, 1.])
+
+
+def test_rowlands_are_oriented_the_same_way():
+    """When there are two rowland tori, they should be oriented the same way."""
+    double = double_rowland_from_channel_distance(100, 500, 1000.0)
+    add_offset_double_rowland_channels(
+        double, offsets={"1": [0, -5, 0], "1m": [0, +5, 0]}
+    )
+    assert_allclose(
+        double["rowland_central"].parametric(0, 0),
+        double["rowland_central_m"].parametric(0, 0),
+    )
+    # The "top" points in the same direction. Of course, they are offset from each other
+    # so the numbers are not exactly the same.
+    assert_allclose(double["rowland_1"].parametric(0, 0), [1000.0, -55.0, 0.0, 1.0])
+    assert_allclose(double["rowland_1m"].parametric(0, 0), [1000.0, 55.0, 0.0, 1.0])