Added tri connectivity property for FE zones with tests

baseclasses/utils/tecplotIO.py

@@ -350,6 +350,15 @@ def __init__(
     def nElements(self) -> int:
         return self.connectivity.shape[0]
 
+    @property
+    def triConnectivity(self) -> npt.NDArray:
+        if self.zoneType == ZoneType.FETRIANGLE:
+            return self.connectivity
+        elif self.zoneType == ZoneType.FEQUADRILATERAL:
+            return np.row_stack((self.connectivity[:, [0, 1, 2]], self.connectivity[:, [0, 2, 3]]))
+        else:
+            raise TypeError(f"'triConnectivity' not supported for {self.zoneType.name} zone type.")
+
     def _validateZoneType(self) -> None:
         supportedZones = [zone.name for zone in ZoneType if zone.name != "ORDERED"]
         if isinstance(self.zoneType, str):

tests/test_tecplotIO.py

@@ -566,3 +566,62 @@ def test_BinaryReadWriteExternal(self):
             title, zones = readTecplot(self.externalFileBinary)
         except Exception as e:
             self.fail(f"Reading external binary file {self.externalFileBinary} failed with error: {e}")
+
+    def test_TriToTriConn(self):
+        # Create a fe ordered tri zone
+        ni, nj = 10, 10
+        nodes, connectivity = createTriGrid(ni, nj)
+        zone = TecplotFEZone(
+            "TriGrid", {"X": nodes[:, 0], "Y": nodes[:, 1]}, connectivity, zoneType=ZoneType.FETRIANGLE
+        )
+
+        triConn = zone.triConnectivity
+
+        np.testing.assert_array_equal(triConn, zone.connectivity)
+
+    def test_QuadToTriConn(self):
+        # Create a fe ordered quad zone
+        ni, nj = 10, 10
+        nodes, connectivity = createQuadGrid(ni, nj)
+        zone = TecplotFEZone(
+            "QuadGrid", {"X": nodes[:, 0], "Y": nodes[:, 1]}, connectivity, zoneType=ZoneType.FEQUADRILATERAL
+        )
+
+        triConn = zone.triConnectivity
+
+        self.assertEqual(triConn.shape, (zone.nElements * 2, 3))
+
+    def test_TriConnBadZoneType(self):
+        # Create an line seg zone
+        ni = 10
+        nodes, connectivity = createLineSegGrid(ni)
+        zone = TecplotFEZone("LineSeg", {"X": nodes[:, 0], "Y": nodes[:, 1]}, connectivity, zoneType=ZoneType.FELINESEG)
+
+        with self.assertRaises(TypeError):
+            triConn = zone.triConnectivity
+
+        # Create a tet zone
+        ni, nj, nk = 10, 10, 10
+        nodes, connectivity = createTetGrid(ni, nj, nk)
+        zone = TecplotFEZone(
+            "TetGrid",
+            {"X": nodes[:, 0], "Y": nodes[:, 1], "Z": nodes[:, 2]},
+            connectivity,
+            zoneType=ZoneType.FETETRAHEDRON,
+        )
+
+        with self.assertRaises(TypeError):
+            triConn = zone.triConnectivity
+
+        # Create a brick zone
+        ni, nj, nk = 10, 10, 10
+        nodes, connectivity = createBrickGrid(ni, nj, nk)
+        zone = TecplotFEZone(
+            "BrickGrid",
+            {"X": nodes[:, 0], "Y": nodes[:, 1], "Z": nodes[:, 2]},
+            connectivity,
+            zoneType=ZoneType.FEBRICK,
+        )
+
+        with self.assertRaises(TypeError):
+            triConn = zone.triConnectivity