MergeProject - support merging projects with different units

src/ifcpatch/ifcpatch/recipes/MergeProject.py

@@ -18,6 +18,7 @@
 
 import ifcopenshell
 import ifcopenshell.util.element
+import ifcopenshell.util.unit
 from typing import Union
 from logging import Logger
 
@@ -30,6 +31,9 @@ class Patcher:
         further processing will be done. This means that you may end up with
         duplicate spatial hierarchies (i.e. 2 sites, 2 buildings, etc).
 
+        Will automatically convert length units in the second model to the main
+        model's unit before merging.
+
         :param filepath: The filepath of the second IFC model to merge into the
             first. The first model is already specified as the input to
             IfcPatch.
@@ -48,6 +52,10 @@ class Patcher:
 
     def patch(self):
         source = ifcopenshell.open(self.filepath)
+        # make sure models units will match
+        if (main_unit := self.get_unit_name(self.file)) != self.get_unit_name(source):
+            source = ifcopenshell.util.unit.convert_file_length_units(source, main_unit)
+
         self.existing_contexts: list[ifcopenshell.entity_instance] = self.file.by_type(
             "IfcGeometricRepresentationContext"
         )
@@ -69,6 +77,17 @@ class Patcher:
 
         self.reuse_existing_contexts()
 
+    def get_unit_name(self, ifc_file: ifcopenshell.file) -> str:
+        length_unit = ifcopenshell.util.unit.get_project_unit(ifc_file, "LENGTHUNIT")
+        names = {
+            "METRE": "METERS",
+            "FOOT": "FEET",
+            "INCH": "INCHES",
+            "MILE": "MILES",
+        }
+        prefix = getattr(length_unit, "Prefix", None) or ""
+        return prefix + names[length_unit.Name.upper()]
+
     def reuse_existing_contexts(self):
         to_delete = set()
 

src/ifcpatch/test/test_MergeProject.py

@@ -0,0 +1,66 @@
+# IfcOpenShell - IFC toolkit and geometry engine
+# Copyright (C) 2022 Dion Moult <dion@thinkmoult.com>
+#
+# This file is part of IfcOpenShell.
+#
+# IfcOpenShell is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Lesser General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# IfcOpenShell is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public License
+# along with IfcOpenShell.  If not, see <http://www.gnu.org/licenses/>.
+
+import ifcpatch
+import ifcopenshell
+import ifcopenshell.api
+import ifcopenshell.util.placement
+import test.bootstrap
+import tempfile
+import numpy as np
+from pathlib import Path
+from typing import Optional
+
+
+class TestMergeProject(test.bootstrap.IFC4):
+    def setup_project(self, ifc_file: Optional[ifcopenshell.file] = None):
+        prefix = None if ifc_file else "MILLI"
+        if ifc_file is None:
+            ifc_file = ifcopenshell.file(schema=self.file.schema)
+
+        project = ifcopenshell.api.run("root.create_entity", ifc_file, ifc_class="IfcProject")
+        unit = ifcopenshell.api.run("unit.add_si_unit", ifc_file, unit_type="LENGTHUNIT", prefix=prefix)
+        ifcopenshell.api.run("unit.assign_unit", ifc_file, units=[unit])
+
+        matrix = np.eye(4)
+        matrix[:, 3] = (1, 2, 3, 1)
+        wall = ifcopenshell.api.run("root.create_entity", ifc_file, ifc_class="IfcWall")
+        ifcopenshell.api.run("geometry.edit_object_placement", ifc_file, product=wall, matrix=matrix, is_si=True)
+        return ifc_file
+
+    def test_run(self):
+        self.file = self.setup_project(self.file)
+        second_file = self.setup_project()
+        temp_path = Path(tempfile.gettempdir()) / "second.ifc"
+        second_file.write(temp_path)
+        output = ifcpatch.execute({"file": self.file, "recipe": "MergeProject", "arguments": [str(temp_path)]})
+
+        assert len(output.by_type("IfcWall")) == 2
+        wall1, wall2 = output.by_type("IfcWall")
+
+        # test that units are converted
+        placement1 = ifcopenshell.util.placement.get_local_placement(wall1.ObjectPlacement)
+        placement2 = ifcopenshell.util.placement.get_local_placement(wall2.ObjectPlacement)
+        to_tuple = lambda arr: tuple(map(tuple, arr))
+        matrix = np.eye(4)
+        matrix[:, 3] = (1, 2, 3, 1)
+        assert to_tuple(placement1) == to_tuple(placement2) == to_tuple(matrix)
+
+
+class TestMergeProjectIFC2X3(test.bootstrap.IFC2X3, TestMergeProject):
+    pass