added padding arg to bounding_region (#2701)

Co-authored-by: Paul Romano <paul.k.romano@gmail.com>

openmc/bounding_box.py

@@ -1,3 +1,4 @@
+from __future__ import annotations
 from typing import Iterable
 
 import numpy as np
@@ -87,3 +88,30 @@ def extent(self):
     @property
     def width(self):
         return self.upper_right - self.lower_left
+
+    def extend(self, padding_distance: float) -> BoundingBox:
+        """Returns an extended bounding box
+
+        Parameters
+        ----------
+        padding_distance : float
+            The distance to enlarge the bounding box by
+
+        Returns
+        -------
+        An enlarged bounding box
+
+        """
+        return BoundingBox(np.array(
+            [
+                self[0][0] - padding_distance,
+                self[0][1] - padding_distance,
+                self[0][2] - padding_distance
+            ]
+        ), np.array(
+            [
+                self[1][0] + padding_distance,
+                self[1][1] + padding_distance,
+                self[1][2] + padding_distance
+            ]
+        ))

openmc/universe.py

@@ -837,7 +837,7 @@ def bounding_box(self):
             coords = dagmc_file['tstt']['nodes']['coordinates'][()]
             lower_left_corner = coords.min(axis=0)
             upper_right_corner = coords.max(axis=0)
-            return (lower_left_corner, upper_right_corner)
+            return openmc.BoundingBox(lower_left_corner, upper_right_corner)
 
     @property
     def filename(self):
@@ -950,7 +950,13 @@ def create_xml_subelement(self, xml_element, memo=None):
         dagmc_element.set('filename', str(self.filename))
         xml_element.append(dagmc_element)
 
-    def bounding_region(self, bounded_type='box', boundary_type='vacuum', starting_id=10000):
+    def bounding_region(
+            self,
+            bounded_type: str = 'box',
+            boundary_type: str = 'vacuum',
+            starting_id: int = 10000,
+            padding_distance: float = 0.
+        ):
         """Creates a either a spherical or box shaped bounding region around
         the DAGMC geometry.
 
@@ -970,6 +976,10 @@ def bounding_region(self, bounded_type='box', boundary_type='vacuum', starting_i
             Starting ID of the surface(s) used in the region. For bounded_type
             'box', the next 5 IDs will also be used. Defaults to 10000 to reduce
             the chance of an overlap of surface IDs with the DAGMC geometry.
+        padding_distance : float
+            Distance between the bounding region surfaces and the minimal
+            bounding box. Allows for the region to be larger than the DAGMC
+            geometry.
 
         Returns
         -------
@@ -983,16 +993,15 @@ def bounding_region(self, bounded_type='box', boundary_type='vacuum', starting_i
         check_type('bounded type', bounded_type, str)
         check_value('bounded type', bounded_type, ('box', 'sphere'))
 
-        bbox = self.bounding_box
+        bbox = self.bounding_box.extend(padding_distance)
 
         if bounded_type == 'sphere':
-            bbox_center = (bbox[0] + bbox[1])/2
-            radius = np.linalg.norm(np.asarray(bbox))
+            radius = np.linalg.norm(bbox.upper_right - bbox.center)
             bounding_surface = openmc.Sphere(
                 surface_id=starting_id,
-                x0=bbox_center[0],
-                y0=bbox_center[1],
-                z0=bbox_center[2],
+                x0=bbox.center[0],
+                y0=bbox.center[1],
+                z0=bbox.center[2],
                 boundary_type=boundary_type,
                 r=radius,
             )

tests/unit_tests/dagmc/test_bounds.py

@@ -23,23 +23,38 @@ def test_bounding_region(request):
     assert isinstance(region, openmc.Region)
     assert len(region) == 6
     assert region[0].surface.type == "x-plane"
+    assert region[0].surface.x0 == -25.
     assert region[1].surface.type == "x-plane"
+    assert region[1].surface.x0 == 25.
     assert region[2].surface.type == "y-plane"
+    assert region[2].surface.y0 == -25.
     assert region[3].surface.type == "y-plane"
+    assert region[3].surface.y0 == 25.
     assert region[4].surface.type == "z-plane"
+    assert region[4].surface.z0 == -25.
     assert region[5].surface.type == "z-plane"
+    assert region[5].surface.z0 == 25.
     assert region[0].surface.boundary_type == "vacuum"
     assert region[1].surface.boundary_type == "vacuum"
     assert region[2].surface.boundary_type == "vacuum"
     assert region[3].surface.boundary_type == "vacuum"
     assert region[4].surface.boundary_type == "vacuum"
     assert region[5].surface.boundary_type == "vacuum"
+    region = u.bounding_region(padding_distance=5)
+    assert region[0].surface.x0 == -30.
+    assert region[1].surface.x0 == 30.
+    assert region[2].surface.y0 == -30.
+    assert region[3].surface.y0 == 30.
+    assert region[4].surface.z0 == -30.
+    assert region[5].surface.z0 == 30.
 
     region = u.bounding_region(bounded_type="sphere", boundary_type="reflective")
     assert isinstance(region, openmc.Region)
     assert isinstance(region, openmc.Halfspace)
     assert region.surface.type == "sphere"
     assert region.surface.boundary_type == "reflective"
+    larger_region = u.bounding_region(bounded_type="sphere", padding_distance=10)
+    assert larger_region.surface.r > region.surface.r
 
 
 def test_bounded_universe(request):