Fixed problem with hollow STL files

src/build123d/exporters.py

@@ -37,6 +37,7 @@ from enum import Enum, auto
 from io import BytesIO
 from os import PathLike, fsdecode
 from typing import Any, TypeAlias
+from typing import cast as tcast
 from warnings import warn
 
 from collections.abc import Callable, Iterable
@@ -48,7 +49,7 @@ from ezdxf.colors import RGB, aci2rgb
 from ezdxf.math import Vec2
 from OCP.BRepLib import BRepLib
 from OCP.BRepTools import BRepTools_WireExplorer
-from OCP.Geom import Geom_BezierCurve
+from OCP.Geom import Geom_BezierCurve, Geom_BSplineCurve
 from OCP.GeomConvert import GeomConvert
 from OCP.GeomConvert import GeomConvert_BSplineCurveToBezierCurve
 from OCP.gp import gp_Ax2, gp_Dir, gp_Pnt, gp_Vec, gp_XYZ
@@ -757,7 +758,7 @@ class ExportDXF(Export2D):
 
         # Extract the relevant segment of the curve.
         spline = GeomConvert.SplitBSplineCurve_s(
-            curve,
+            tcast(Geom_BSplineCurve, curve),
             u1,
             u2,
             Export2D.PARAMETRIC_TOLERANCE,
@@ -1136,7 +1137,7 @@ class ExportSVG(Export2D):
         )
         while explorer.More():
             topo_edge = explorer.Current()
-            loose_edges.append(Edge(topo_edge))
+            loose_edges.append(Edge(TopoDS.Edge_s(topo_edge)))
             explorer.Next()
         # print(f"{len(loose_edges)} loose edges")
         loose_edge_elements = [self._edge_element(edge) for edge in loose_edges]
@@ -1263,7 +1264,7 @@ class ExportSVG(Export2D):
         (u0, u1) = (lp, fp) if reverse else (fp, lp)
         start = self._path_point(curve.Value(u0))
         end = self._path_point(curve.Value(u1))
-        radius = complex(radius, radius)
+        radius = complex(radius, radius)  # type: ignore[assignment]
         rotation = math.degrees(gp_Dir(1, 0, 0).AngleWithRef(x_axis, gp_Dir(0, 0, 1)))
         if curve.IsClosed():
             midway = self._path_point(curve.Value((u0 + u1) / 2))
@@ -1316,7 +1317,7 @@ class ExportSVG(Export2D):
         (u0, u1) = (lp, fp) if reverse else (fp, lp)
         start = self._path_point(curve.Value(u0))
         end = self._path_point(curve.Value(u1))
-        radius = complex(major_radius, minor_radius)
+        radius = complex(major_radius, minor_radius)  # type: ignore[assignment]
         rotation = math.degrees(gp_Dir(1, 0, 0).AngleWithRef(x_axis, gp_Dir(0, 0, 1)))
         if curve.IsClosed():
             midway = self._path_point(curve.Value((u0 + u1) / 2))
@@ -1361,7 +1362,7 @@ class ExportSVG(Export2D):
         # According to the OCCT 7.6.0 documentation,
         # "ParametricTolerance is not used."
         converter = GeomConvert_BSplineCurveToBezierCurve(
-            spline, u1, u2, Export2D.PARAMETRIC_TOLERANCE
+            tcast(Geom_BSplineCurve, spline), u1, u2, Export2D.PARAMETRIC_TOLERANCE
         )
 
         def make_segment(bezier: Geom_BezierCurve, reverse: bool) -> PathSegment:

src/build123d/exporters3d.py

@@ -244,7 +244,7 @@ def export_gltf(
 
     messenger = Message.DefaultMessenger_s()
     for printer in messenger.Printers():
-        printer.SetTraceLevel(Message_Gravity(Message_Gravity.Message_Fail))
+        printer.SetTraceLevel(Message_Gravity.Message_Fail)
 
     status = writer.Perform(doc, index_map, progress)
 
@@ -297,7 +297,7 @@ def export_step(
     # Disable writing OCCT info to console
     messenger = Message.DefaultMessenger_s()
     for printer in messenger.Printers():
-        printer.SetTraceLevel(Message_Gravity(Message_Gravity.Message_Fail))
+        printer.SetTraceLevel(Message_Gravity.Message_Fail)
 
     session = XSControl_WorkSession()
     writer = STEPCAFControl_Writer(session, False)
@@ -328,7 +328,7 @@ def export_step(
 
     if not isinstance(file_path, BytesIO):
         status = (
-            writer.Write(fspath(file_path)) == IFSelect_ReturnStatus.IFSelect_RetDone
+            writer.Write(fsdecode(file_path)) == IFSelect_ReturnStatus.IFSelect_RetDone
         )
     else:
         status = writer.WriteStream(file_path) == IFSelect_ReturnStatus.IFSelect_RetDone

src/build123d/mesher.py

@@ -106,15 +106,23 @@ from OCP.BRepGProp import BRepGProp
 from OCP.BRepMesh import BRepMesh_IncrementalMesh
 from OCP.gp import gp_Pnt
 from OCP.GProp import GProp_GProps
+from OCP.Standard import Standard_TypeMismatch
 from OCP.TopAbs import TopAbs_ShapeEnum
 from OCP.TopExp import TopExp_Explorer
 from OCP.TopLoc import TopLoc_Location
-from OCP.TopoDS import TopoDS_Compound
+from OCP.TopoDS import TopoDS, TopoDS_Compound, TopoDS_Shell
 from lib3mf import Lib3MF
 
 from build123d.build_enums import MeshType, Unit
 from build123d.geometry import TOLERANCE, Color
-from build123d.topology import Compound, Shape, Shell, Solid, downcast
+from build123d.topology import (
+    Compound,
+    Shape,
+    Shell,
+    Solid,
+    downcast,
+    unwrap_topods_compound,
+)
 
 
 class Mesher:
@@ -466,7 +474,9 @@ class Mesher:
             # Convert to a list of gp_Pnt
             ocp_vertices = [gp_pnts[tri_indices[i]] for i in range(3)]
             # Create the triangular face using the polygon
-            polygon_builder = BRepBuilderAPI_MakePolygon(*ocp_vertices, Close=True)
+            polygon_builder = BRepBuilderAPI_MakePolygon(
+                ocp_vertices[0], ocp_vertices[1], ocp_vertices[2], Close=True
+            )
             face_builder = BRepBuilderAPI_MakeFace(polygon_builder.Wire())
             facet = face_builder.Face()
             facet_properties = GProp_GProps()
@@ -479,19 +489,27 @@ class Mesher:
         occ_sewed_shape = downcast(shell_builder.SewedShape())
 
         if isinstance(occ_sewed_shape, TopoDS_Compound):
-            occ_shells = []
+            bd_shells = []
             explorer = TopExp_Explorer(occ_sewed_shape, TopAbs_ShapeEnum.TopAbs_SHELL)
             while explorer.More():
-                occ_shells.append(downcast(explorer.Current()))
+                # occ_shells.append(downcast(explorer.Current()))
+                bd_shells.append(Shell(TopoDS.Shell_s(explorer.Current())))
                 explorer.Next()
         else:
-            occ_shells = [occ_sewed_shape]
+            assert isinstance(occ_sewed_shape, TopoDS_Shell)
+            bd_shells = [Shell(occ_sewed_shape)]
 
-        # Create a solid if manifold
-        shape_obj = Shell(occ_sewed_shape)
-        if shape_obj.is_manifold:
-            solid_builder = BRepBuilderAPI_MakeSolid(*occ_shells)
-            shape_obj = Solid(solid_builder.Solid())
+        outer_shell = max(bd_shells, key=lambda s: math.prod(s.bounding_box().size))
+        inner_shells = [s for s in bd_shells if s is not outer_shell]
+
+        # The the shell isn't water tight just return it else create a solid
+        if not outer_shell.is_manifold:
+            return outer_shell
+
+        solid_builder = BRepBuilderAPI_MakeSolid(outer_shell.wrapped)
+        for inner_shell in inner_shells:
+            solid_builder.Add(inner_shell.wrapped)
+        shape_obj = Solid(solid_builder.Solid())
 
         return shape_obj
 

src/build123d/topology/composite.py

@@ -60,7 +60,6 @@ import sys
 import warnings
 from collections.abc import Iterable, Iterator, Sequence
 from itertools import combinations
-from typing import TypeVar
 
 from typing_extensions import Self
 

tests/test_mesher.py

@@ -210,6 +210,7 @@ class TestHollowImport(unittest.TestCase):
         importer = Mesher()
         stl = importer.read("test.stl")
         self.assertTrue(stl[0].is_valid)
+        self.assertAlmostEqual(test_shape.volume, stl[0].volume, 0)
 
 
 class TestImportDegenerateTriangles(unittest.TestCase):