Added import_stl as Solid

pyproject.toml

@@ -43,7 +43,8 @@ dependencies = [
     "numpy >= 1.24.1, <2",
     "svgpathtools >= 1.5.1, <2",
     "anytree >= 2.8.0, <3",
-    "ezdxf >= 1.0.0, < 2"
+    "ezdxf >= 1.0.0, < 2",
+    "numpy-stl >= 3.0.0, <4"
 ]
 
 [tool.setuptools.packages.find]

src/build123d/importers.py

@@ -30,15 +30,26 @@ license:
 
 import os
 from math import degrees
+from stl.mesh import Mesh
 from svgpathtools import svg2paths
+from typing import Union
 from OCP.TopoDS import TopoDS_Face, TopoDS_Shape
 from OCP.BRep import BRep_Builder
 from OCP.BRepTools import BRepTools
 from OCP.STEPControl import STEPControl_Reader
 import OCP.IFSelect
 from OCP.RWStl import RWStl
+from OCP.BRepBuilderAPI import (
+    BRepBuilderAPI_MakeEdge,
+    BRepBuilderAPI_MakeFace,
+    BRepBuilderAPI_MakeSolid,
+    BRepBuilderAPI_MakeVertex,
+    BRepBuilderAPI_MakeWire,
+    BRepBuilderAPI_Sewing,
+)
+from OCP.gp import gp_Pnt
 
-from build123d.topology import Compound, Edge, Face, Shape, ShapeList
+from build123d.topology import Compound, Edge, Face, Shape, ShapeList, Solid, downcast
 
 
 def import_brep(file_name: str) -> Shape:
@@ -98,27 +109,78 @@ def import_step(file_name: str) -> Compound:
     return Compound.make_compound(solids)
 
 
-def import_stl(file_name: str) -> Face:
+def import_stl(file_name: str, for_reference: bool = True) -> Union[Face, Solid]:
     """import_stl
 
-    Extract shape from an STL file and return them as a Face object.
+    Extract shape from an STL file and return them as a Solid object.
 
     Args:
         file_name (str): file path of STL file to import
+        for_reference (bool, optional): only create an uneditable mesh object
+            for use as a reference. Otherwise, create an editable Solid object.
+            Note that creating a reference is very fast while creating an editable
+            model may take minutes depending on the size of the STL file.
+            Defaults to True.
 
     Raises:
         ValueError: Could not import file
 
     Returns:
-        Face: contents of STL file
+        Union[Face, Solid]: STL model
     """
-    # Now read and return the shape
-    reader = RWStl.ReadFile_s(file_name)
-    face = TopoDS_Face()
+    if for_reference:
+        # Now read and return the shape
+        reader = RWStl.ReadFile_s(file_name)
+        face = TopoDS_Face()
+        BRep_Builder().MakeFace(face, reader)
+        stl_obj = Face.cast(face)
+    else:
+        # Read the file with numpy-stl
+        try:
+            stl_mesh = Mesh.from_file(file_name)
+        except:
+            raise ValueError("Invalid file")
 
-    BRep_Builder().MakeFace(face, reader)
+        faces = []
 
-    return Face.cast(face)
+        for facet in stl_mesh.vectors:
+            # Create OCC vertices
+            ocp_vertices = [
+                downcast(BRepBuilderAPI_MakeVertex(gp_Pnt(x, y, z)).Vertex())
+                for x, y, z in facet
+            ]
+
+            # Create OCC edges
+            ocp_edges = [
+                BRepBuilderAPI_MakeEdge(v1, v2).Edge()
+                for v1, v2 in zip(ocp_vertices, ocp_vertices[1:] + [ocp_vertices[0]])
+            ]
+
+            # Create OCC wire
+            wire_builder = BRepBuilderAPI_MakeWire()
+            for edge in ocp_edges:
+                wire_builder.Add(edge)
+            ocp_wire = wire_builder.Wire()
+
+            # Create OCC face
+            face_builder = BRepBuilderAPI_MakeFace(ocp_wire)
+            ocp_face = face_builder.Face()
+
+            # Store the faces
+            faces.append(ocp_face)
+
+        # Create a shell
+        shell_builder = BRepBuilderAPI_Sewing()
+        for face in faces:
+            shell_builder.Add(face)
+        shell_builder.Perform()
+        occ_shell = downcast(shell_builder.SewedShape())
+
+        # Create a solid
+        solid_builder = BRepBuilderAPI_MakeSolid(occ_shell)
+        stl_obj = Solid(solid_builder.Solid())
+
+    return stl_obj
 
 
 def import_svg_as_buildline_code(file_name: str) -> tuple[str, str]:

tests/test_direct_api.py

@@ -1141,7 +1141,7 @@ class TestFunctions(unittest.TestCase):
         self.assertEqual(plug[0], cyl)
 
 
-class TestImportExport(unittest.TestCase):
+class TestImportExport(DirectApiTestCase):
     def test_import_export(self):
         original_box = Solid.make_box(1, 1, 1)
         original_box.export_step("test_box.step")
@@ -1157,6 +1157,22 @@ class TestImportExport(unittest.TestCase):
         with self.assertRaises(ValueError):
             step_box = import_step("test_box.step")
 
+    def test_import_stl(self):
+        original_box = Solid.make_box(1, 2, 3)
+        original_box.export_stl("test_box.stl")
+        stl_box = import_stl("test_box.stl", for_reference=False).clean()
+        self.assertEqual(len(stl_box.vertices()), 8)
+        self.assertEqual(len(stl_box.edges()), 12)
+        self.assertEqual(len(stl_box.faces()), 6)
+        self.assertAlmostEqual(stl_box.volume, 1 * 2 * 3, 5)
+
+        stl_box = import_stl("test_box.stl", for_reference=True)
+        self.assertVectorAlmostEquals(stl_box.position, (0, 0, 0), 5)
+
+        os.remove("test_box.stl")
+        with self.assertRaises(ValueError):
+            import_stl("test_box.stl", for_reference=False)
+
 
 class TestJoints(DirectApiTestCase):
     def test_rigid_joint(self):