Allowing Shell to take a single Face Issue #531

src/build123d/topology.py

@@ -95,6 +95,7 @@
     BRepBuilderAPI_MakeEdge,
     BRepBuilderAPI_MakeFace,
     BRepBuilderAPI_MakePolygon,
+    BRepBuilderAPI_MakeShell,
     BRepBuilderAPI_MakeSolid,
     BRepBuilderAPI_MakeVertex,
     BRepBuilderAPI_MakeWire,
@@ -6076,6 +6077,23 @@ def __init__(
             parent (Compound, optional): assembly parent. Defaults to None.
         """
 
+    @overload
+    def __init__(
+        self,
+        face: Face,
+        label: str = "",
+        color: Color = None,
+        parent: Compound = None,
+    ):
+        """Build a shell from a single Face
+
+        Args:
+            face (Face): Face to convert to Shell
+            label (str, optional): Defaults to ''.
+            color (Color, optional): Defaults to None.
+            parent (Compound, optional): assembly parent. Defaults to None.
+        """
+
     @overload
     def __init__(
         self,
@@ -6094,29 +6112,42 @@ def __init__(
         """
 
     def __init__(self, *args, **kwargs):
-        faces, obj, label, color, parent = (None,) * 5
+        face, faces, obj, label, color, parent = (None,) * 6
 
         if args:
             l_a = len(args)
             if isinstance(args[0], TopoDS_Shape):
                 obj, label, color, parent = args[:4] + (None,) * (4 - l_a)
+            elif isinstance(args[0], Face):
+                face, label, color, parent = args[:4] + (None,) * (4 - l_a)
             elif isinstance(args[0], Iterable):
                 faces, label, color, parent = args[:4] + (None,) * (4 - l_a)
 
         unknown_args = ", ".join(
-            set(kwargs.keys()).difference(["faces", "obj", "label", "color", "parent"])
+            set(kwargs.keys()).difference(
+                ["face", "faces", "obj", "label", "color", "parent"]
+            )
         )
         if unknown_args:
             raise ValueError(f"Unexpected argument(s) {unknown_args}")
 
         obj = kwargs.get("obj", obj)
+        face = kwargs.get("face", face)
         faces = kwargs.get("faces", faces)
         label = kwargs.get("label", label)
         color = kwargs.get("color", color)
         parent = kwargs.get("parent", parent)
 
         if faces:
-            obj = Shell._make_shell(faces)
+            if len(faces) == 1:
+                face = faces[0]
+            else:
+                obj = Shell._make_shell(faces)
+        if face:
+            builder = BRepBuilderAPI_MakeShell(
+                BRepAdaptor_Surface(face.wrapped).Surface().Surface()
+            )
+            obj = builder.Shape()
 
         super().__init__(
             obj=obj,

tests/test_direct_api.py

@@ -46,7 +46,7 @@
 from build123d.build_part import BuildPart
 from build123d.operations_part import extrude
 from build123d.operations_sketch import make_face
-from build123d.operations_generic import fillet, add
+from build123d.operations_generic import fillet, add, sweep
 from build123d.objects_part import Box, Cylinder
 from build123d.objects_curve import Polyline
 from build123d.build_sketch import BuildSketch
@@ -3087,6 +3087,13 @@ def test_constructor(self):
         with self.assertRaises(ValueError):
             Shell(bob="fred")
 
+        x_section = Rot(90) * Spline((0, -5), (-3, -2), (-2, 0), (-3, 2), (0, 5))
+        surface = sweep(x_section, Circle(5).wire())
+        single_face = Shell(surface.face())
+        self.assertTrue(single_face.is_valid())
+        single_face = Shell(surface.faces())
+        self.assertTrue(single_face.is_valid())
+
 
 class TestSolid(DirectApiTestCase):
     def test_make_solid(self):
@@ -3675,7 +3682,7 @@ def test_constructor(self):
         self.assertTupleAlmostEquals(w6.color.to_tuple(), (1.0, 0.0, 0.0, 1.0), 5)
         w7 = Wire(w6)
         self.assertTrue(w7.is_valid())
-        c0 = Polyline((0,0),(1,0),(1,1))
+        c0 = Polyline((0, 0), (1, 0), (1, 1))
         w8 = Wire(c0)
         self.assertTrue(w8.is_valid())
         with self.assertRaises(ValueError):