Added materials support by postfixing the material name onto the volume

.github/workflows/tests.yml

@@ -40,5 +40,6 @@ jobs:
       - name: Install dependencies
         run: |
           python -m pip install .[dev]
+          python -m pip install --upgrade git+https://github.com/CadQuery/cadquery.git
       - name: Run tests
         run: python -m pytest -v

assembly_mesh_plugin/plugin.py

@@ -161,6 +161,7 @@ def get_gmsh(self, imprint=True):
     tagged_faces = {}
     multi_material_groups = {}
     surface_groups = {}
+    solid_materials = []
 
     gmsh.initialize()
     gmsh.option.setNumber(
@@ -171,13 +172,23 @@ def get_gmsh(self, imprint=True):
     # Get all of the subshapes and their corresponding names/positions
     extract_subshape_names(self, self.name)
 
-    # Imprint the assembly
-    imprinted_assembly, imprinted_solids_with_orginal_ids = (
-        cq.occ_impl.assembly.imprint(self)
-    )
-
     # Handle the imprinted assembly
     if imprint:
+        # Imprint the assembly
+        imprinted_assembly, imprinted_solids_with_orginal_ids = (
+            cq.occ_impl.assembly.imprint(self)
+        )
+
+        # Collect the materials
+        for imp_solid, solid_id in imprinted_solids_with_orginal_ids.items():
+            # Track down the original assembly object so that we can retrieve materials, if present
+            short_id = solid_id[0].split("/")[-1] if "/" in solid_id[0] else solid_id[0]
+            subassy = self.objects[short_id]
+
+            # Save the assembly material associated with this solid
+            if subassy.material:
+                solid_materials.append(subassy.material.name)
+
         for solid, name in imprinted_solids_with_orginal_ids.items():
             # Get just the name of the current assembly
             short_name = name[0].split("/")[-1]
@@ -202,12 +213,23 @@ def get_gmsh(self, imprint=True):
                 # Add faces to the mesh and handle tagged faces
                 add_faces_to_mesh(gmsh, solid, short_name, loc)
 
+            # Keep track of the materials
+            if self.objects[name.split("/")[-1]].material:
+                solid_materials.append(self.objects[name.split("/")[-1]].material.name)
+
     # Step through each of the volumes and add physical groups for each
     for volume_id in volumes.keys():
         gmsh.model.occ.synchronize()
+
+        # Attach the name to the volume
         ps = gmsh.model.addPhysicalGroup(3, volumes[volume_id][0])
         gmsh.model.setPhysicalName(3, ps, f"{volume_map[volume_id]}")
 
+        # Attach the material to the volume, if the material is present
+        if len(solid_materials) >= volume_id:
+            ps1 = gmsh.model.addPhysicalGroup(3, volumes[volume_id][0])
+            gmsh.model.setPhysicalName(3, ps1, f"mat:{solid_materials[volume_id - 1]}")
+
     # Handle tagged surface groups
     for t_name, surf_group in surface_groups.items():
         gmsh.model.occ.synchronize()

tests/sample_assemblies.py

@@ -315,3 +315,20 @@ def generate_subshape_assembly():
     )
 
     return assy
+
+
+def generate_materials_assembly():
+    """
+    Generates a simple assembly with materials.
+    """
+
+    # Create the assembly children
+    cube_1 = cq.Workplane().box(10, 10, 10)
+    cube_2 = cq.Workplane().box(5, 5, 5)
+
+    # Put the assembly together
+    assy = cq.Assembly(name="top-level")
+    assy.add(cube_1, name="cube_1", material="copper")
+    assy.add(cube_2, name="cube_2", loc=cq.Location(0, 0, 5), material="steel")
+
+    return assy

tests/test_meshes.py

@@ -8,6 +8,7 @@
     generate_test_cross_section,
     generate_assembly,
     generate_subshape_assembly,
+    generate_materials_assembly,
 )
 
 
@@ -175,3 +176,48 @@ def _check_physical_groups():
 
     # Ensure that there are physical groups
     _check_physical_groups()
+
+
+def test_mesh_materials():
+    """
+    Tests to make sure that assembly materials are preserved in the mesh data.
+    """
+
+    # Create the basic assembly with materials
+    assy = generate_materials_assembly()
+
+    #
+    # Imprinted assembly
+    #
+    gmsh = assy.getGmsh(imprint=True)
+    gmsh.model.mesh.generate(3)
+
+    phys_groups = gmsh.model.getPhysicalGroups(3)
+
+    # Make sure we got the correct names
+    name = gmsh.model.getPhysicalName(3, 1)
+    assert name == "cube_1"
+    name = gmsh.model.getPhysicalName(3, 2)
+    assert name == "mat:copper"
+    name = gmsh.model.getPhysicalName(3, 3)
+    assert name == "cube_2"
+    name = gmsh.model.getPhysicalName(3, 4)
+    assert name == "mat:steel"
+
+    #
+    # Non-imprinted assembly
+    #
+    gmsh = assy.getGmsh(imprint=False)
+    gmsh.model.mesh.generate(3)
+
+    phys_groups = gmsh.model.getPhysicalGroups(3)
+
+    # Make sure we got the correct names
+    name = gmsh.model.getPhysicalName(3, 1)
+    assert name == "cube_1"
+    name = gmsh.model.getPhysicalName(3, 2)
+    assert name == "mat:copper"
+    name = gmsh.model.getPhysicalName(3, 3)
+    assert name == "cube_2"
+    name = gmsh.model.getPhysicalName(3, 4)
+    assert name == "mat:steel"