From 76c1a26f26c63439dfac57dd46c6100691ad2182 Mon Sep 17 00:00:00 2001
From: Patrick Shriwise <pshriwise@gmail.com>
Date: Thu, 15 Feb 2024 23:52:32 -0600
Subject: [PATCH] Adding area and volume methods and tests

---
 dagmc/dagnav.py    | 24 ++++++++++++++++++++++++
 test/test_basic.py | 29 +++++++++++++++++++++++++++++
 2 files changed, 53 insertions(+)

diff --git a/dagmc/dagnav.py b/dagmc/dagnav.py
index 8327600..3963f58 100644
--- a/dagmc/dagnav.py
+++ b/dagmc/dagnav.py
@@ -370,6 +370,16 @@ def num_triangles(self):
     def _get_triangle_sets(self):
         return [self]
 
+    @property
+    def area(self):
+        """Returns the area of the surface"""
+        conn, coords = self.get_triangle_conn_and_coords()
+        sum = 0.0
+        for _conn in conn:
+            tri_coords = coords[_conn]
+            sum += np.linalg.norm(np.cross(tri_coords[1] - tri_coords[0], tri_coords[2] - tri_coords[0]))
+        return 0.5 * sum
+
 
 class Volume(DAGSet):
 
@@ -427,6 +437,20 @@ def num_triangles(self):
     def _get_triangle_sets(self):
         return [s.handle for s in self.get_surfaces().values()]
 
+    @property
+    def volume(self):
+        """Returns the volume of the volume"""
+        volume = 0.0
+        for surface in self.get_surfaces().values():
+            conn, coords = surface.get_triangle_conn_and_coords()
+            sum = 0.0
+            for _conn in conn:
+                tri_coords = coords[_conn]
+                c = np.cross(tri_coords[1] - tri_coords[0], tri_coords[2] - tri_coords[0])
+                sum += np.dot(c, tri_coords[0])
+            sign = 1 if surface.forward_volume == self else -1
+            volume += sign * sum
+        return volume / 6.0
 
 class Group(DAGSet):
 
diff --git a/test/test_basic.py b/test/test_basic.py
index be68861..e10240d 100644
--- a/test/test_basic.py
+++ b/test/test_basic.py
@@ -2,6 +2,8 @@
 import urllib.request
 
 import pytest
+import numpy as np
+
 from test import config
 
 from pymoab import core
@@ -297,3 +299,30 @@ def test_write(request, tmpdir):
 
     model = dagmc.DAGModel('fuel_pin_copy.h5m')
     assert 12345 in model.volumes
+
+
+def test_volume(request):
+    test_file = str(request.path.parent / 'fuel_pin.h5m')
+    model = dagmc.DAGModel(test_file)
+    exp_vols = {1: np.pi * 7**2 * 40,
+                2: np.pi * (9**2 - 7**2) * 40,
+                3: np.pi * (10**2 - 9**2) * 40,}
+    pytest.approx(model.volumes[1].volume, exp_vols[1])
+    pytest.approx(model.volumes[2].volume, exp_vols[2])
+    pytest.approx(model.volumes[3].volume, exp_vols[3])
+
+
+def test_area(request):
+    test_file = str(request.path.parent / 'fuel_pin.h5m')
+    model = dagmc.DAGModel(test_file)
+    exp_areas = {1: 2 * np.pi * 7 * 40,
+                 2: np.pi * 7**2,
+                 3: np.pi * 7**2,
+                 5: 2 * np.pi * 9 * 40,
+                 6: np.pi * 9**2,
+                 7: np.pi * 9**2,
+                 9: 2 * np.pi * 10 * 40,
+                 10: np.pi * 10**2,
+                 11: np.pi * 10**2 }
+    for surf_id, exp_area in exp_areas.items():
+        pytest.approx(model.surfaces[surf_id].area, exp_area)
\ No newline at end of file