From cce80fe7da8b32631601afe72464f76b1ef13335 Mon Sep 17 00:00:00 2001
From: Christopher Billingham <cbillingham@gmail.com>
Date: Sun, 6 Aug 2023 01:31:38 +0100
Subject: [PATCH] Spherical bb (#2620)

Co-authored-by: Jonathan Shimwell <drshimwell@gmail.com>
Co-authored-by: Paul Romano <paul.k.romano@gmail.com>
---
 openmc/mesh.py                | 26 ++++++++++++++++++++++++++
 tests/unit_tests/test_mesh.py | 22 +++++++++++++++++++++-
 2 files changed, 47 insertions(+), 1 deletion(-)

diff --git a/openmc/mesh.py b/openmc/mesh.py
index a878d4f7127..30ad738a20b 100644
--- a/openmc/mesh.py
+++ b/openmc/mesh.py
@@ -505,6 +505,9 @@ class RegularMesh(StructuredMesh):
     upper_right : Iterable of float
         The upper-right corner of the structured mesh. If only two coordinate
         are given, it is assumed that the mesh is an x-y mesh.
+    bounding_box: openmc.BoundingBox
+        Axis-aligned bounding box of the cell defined by the upper-right and lower-
+        left coordinates
     width : Iterable of float
         The width of mesh cells in each direction.
     indices : Iterable of tuple
@@ -1549,6 +1552,15 @@ class SphericalMesh(StructuredMesh):
     indices : Iterable of tuple
         An iterable of mesh indices for each mesh element, e.g. [(1, 1, 1),
         (2, 1, 1), ...]
+    lower_left : numpy.ndarray
+        The lower-left corner of the structured mesh. If only two coordinate
+        are given, it is assumed that the mesh is an x-y mesh.
+    upper_right : numpy.ndarray
+        The upper-right corner of the structured mesh. If only two coordinate
+        are given, it is assumed that the mesh is an x-y mesh.
+    bounding_box : openmc.BoundingBox
+        Axis-aligned bounding box of the cell defined by the upper-right and lower-
+        left coordinates
 
     """
 
@@ -1629,6 +1641,20 @@ def indices(self):
                 for t in range(1, nt + 1)
                 for r in range(1, nr + 1))
 
+    @property
+    def lower_left(self):
+        r = self.r_grid[-1]
+        return np.array((self.origin[0] - r, self.origin[1] - r, self.origin[2] - r))
+
+    @property
+    def upper_right(self):
+        r = self.r_grid[-1]
+        return np.array((self.origin[0] + r, self.origin[1] + r, self.origin[2] + r))
+
+    @property
+    def bounding_box(self):
+        return openmc.BoundingBox(self.lower_left, self.upper_right)
+
     def __repr__(self):
         fmt = '{0: <16}{1}{2}\n'
         string = super().__repr__()
diff --git a/tests/unit_tests/test_mesh.py b/tests/unit_tests/test_mesh.py
index affbcabd206..60d14a27929 100644
--- a/tests/unit_tests/test_mesh.py
+++ b/tests/unit_tests/test_mesh.py
@@ -38,7 +38,7 @@ def test_raises_error_when_flat(val_left, val_right):
         mesh.lower_left = [-25, -25, val_left]
 
 
-def test_mesh_bounding_box():
+def test_regular_mesh_bounding_box():
     mesh = openmc.RegularMesh()
     mesh.lower_left = [-2, -3, -5]
     mesh.upper_right = [2, 3, 5]
@@ -48,6 +48,26 @@ def test_mesh_bounding_box():
     np.testing.assert_array_equal(bb.upper_right, np.array([2, 3, 5]))
 
 
+def test_spherical_mesh_bounding_box():
+    # test with mesh at origin (0, 0, 0)
+    mesh = openmc.SphericalMesh([0.1, 0.2, 0.5, 1.], origin=(0., 0., 0.))
+    np.testing.assert_array_equal(mesh.upper_right, (1, 1, 1))
+    np.testing.assert_array_equal(mesh.lower_left, (-1, -1, -1))
+    bb = mesh.bounding_box
+    assert isinstance(bb, openmc.BoundingBox)
+    np.testing.assert_array_equal(bb.lower_left, (-1, -1, -1))
+    np.testing.assert_array_equal(bb.upper_right, (1, 1, 1))
+
+    # test with mesh at origin (3, 5, 7)
+    mesh.origin = (3, 5, 7)
+    np.testing.assert_array_equal(mesh.upper_right, (4, 6, 8))
+    np.testing.assert_array_equal(mesh.lower_left, (2, 4, 6))
+    bb = mesh.bounding_box
+    assert isinstance(bb, openmc.BoundingBox)
+    np.testing.assert_array_equal(bb.lower_left, (2, 4, 6))
+    np.testing.assert_array_equal(bb.upper_right, (4, 6, 8))
+
+
 def test_SphericalMesh_initiation():
 
     # test defaults