adding plot function to DAGMCUnvierse (#3451)

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

Author: shimwell

openmc/dagmc.py

@@ -13,6 +13,7 @@
 from .surface import _BOUNDARY_TYPES
 from .bounding_box import BoundingBox
 from .utility_funcs import input_path
+from .plots import add_plot_params
 
 
 class DAGMCUniverse(openmc.UniverseBase):
@@ -566,6 +567,21 @@ def sync_dagmc_cells(self, mats: Iterable[openmc.Material]):
                 fill = mats_per_id[dag_cell.fill.id] if dag_cell.fill else None
             self.add_cell(openmc.DAGMCCell(cell_id=dag_cell_id, fill=fill))
 
+    @add_plot_params
+    def plot(self, *args, **kwargs):
+        """Display a slice plot of the DAGMCUniverse.
+        """
+        model = openmc.Model()
+        model.geometry = openmc.Geometry(self)
+
+        for mat_name in self.material_names:
+            material = openmc.Material(name=mat_name)
+            # Placeholder nuclide to ensure material is not empty
+            material.add_nuclide('H1', 1.0)
+            model.materials.append(material)
+
+        return model.plot(*args, **kwargs)
+
 
 class DAGMCCell(openmc.Cell):
     """A cell class for DAGMC-based geometries.

tests/unit_tests/dagmc/test_plot.py

@@ -7,9 +7,9 @@
     not openmc.lib._dagmc_enabled(), reason="DAGMC CAD geometry is not enabled."
 )
 
-def test_plotting_dagmc_geometry(request):
-    """Test plotting a DAGMC geometry with OpenMC. This is different to CSG
-    geometry plotting as the path to the DAGMC file needs handling."""
+def test_plotting_dagmc_model(request):
+    """Test plotting a DAGMC model with OpenMC. This is different to CSG
+    model plotting as the path to the DAGMC file needs handling."""
 
     dag_universe = openmc.DAGMCUniverse(request.path.parent / 'dagmc.h5m')
     csg_with_dag_inside = dag_universe.bounded_universe()
@@ -30,3 +30,11 @@ def test_plotting_dagmc_geometry(request):
     model.settings.particles = 50
 
     model.plot()
+
+
+def test_plotting_dagmc_universe(request):
+    """Test plotting a DAGMCUniverse with OpenMC. This is different to plotting
+    UniverseBase as the materials are not defined withing the DAGMCUniverse."""
+
+    dag_universe = openmc.DAGMCUniverse(request.path.parent / 'dagmc.h5m')
+    dag_universe.plot()