Swapping a Blender material for another is now auto synchronised.

src/blenderbim/blenderbim/bim/export_ifc.py

@@ -45,7 +45,7 @@ class IfcExporter:
         IfcStore.update_cache()
         if bpy.context.scene.BIMProjectProperties.is_authoring:
             self.sync_deletions()
-            self.sync_object_placements()
+            self.sync_all_objects()
             self.sync_edited_objects()
         extension = self.ifc_export_settings.output_file.split(".")[-1]
         if extension == "ifczip":
@@ -98,10 +98,11 @@ class IfcExporter:
             ifcopenshell.api.run("root.remove_product", self.file, **{"product": product})
         return results
 
-    def sync_object_placements(self):
+    def sync_all_objects(self):
         results = []
         self.unit_scale = ifcopenshell.util.unit.calculate_unit_scale(self.file)
-        for ifc_definition_id, obj in IfcStore.id_map.items():
+        for ifc_definition_id in list(IfcStore.id_map.keys()):
+            obj = IfcStore.id_map[ifc_definition_id]
             try:
                 if isinstance(obj, bpy.types.Material):
                     continue
@@ -109,6 +110,9 @@ class IfcExporter:
                 result = self.sync_object_placement(obj)
                 if result:
                     results.append(result)
+                result = self.sync_object_material(obj)
+                if result:
+                    results.append(result)
             except ReferenceError:
                 pass  # The object is likely deleted
         return results
@@ -131,6 +135,17 @@ class IfcExporter:
         IfcStore.edited_objs.clear()
         return results
 
+    def sync_object_material(self, obj):
+        if not obj.data or not isinstance(obj.data, bpy.types.Mesh):
+            return
+        if not self.has_changed_materials(obj):
+            return
+        bpy.ops.bim.update_representation(obj=obj.name)
+
+    def has_changed_materials(self, obj):
+        checksum = obj.data.BIMMeshProperties.material_checksum
+        return checksum != str([s.id() for s in tool.Geometry.get_styles(obj) if s])
+
     def sync_object_placement(self, obj):
         if not self.has_object_moved(obj):
             return

src/blenderbim/blenderbim/bim/import_ifc.py

@@ -68,6 +68,7 @@ class MaterialCreator:
         self.add_default_material(element)
         if self.parse_representations(element):
             self.assign_material_slots_to_faces()
+        tool.Geometry.record_object_materials(obj)
 
     def add_default_material(self, element):
         element_material = ifcopenshell.util.element.get_material(element)

src/blenderbim/blenderbim/bim/module/gis/operator.py

@@ -19,6 +19,7 @@
 import bpy
 from bpy.types import Operator
 
+
 class BIM_OT_cityjson2ifc(Operator):
     bl_idname = "bim.convert_cityjson2ifc"
     bl_label = "Convert CityJSON to IFC"
@@ -27,7 +28,7 @@ class BIM_OT_cityjson2ifc(Operator):
     def execute(self, context):
         from cjio import cityjson
         from ifccityjson.cityjson2ifc.cityjson2ifc import Cityjson2ifc
-        
+
         props = context.scene.ifccityjson_properties
         city_model = cityjson.load(props.input, transform=False)
         data = {
@@ -53,7 +54,7 @@ class BIM_OT_find_cityjson_lod(Operator):
 
     def execute(self, context):
         from cjio import cityjson
-        
+
         props = context.scene.ifccityjson_properties
         city_model = cityjson.load(props.input)
         lods = set()

src/blenderbim/blenderbim/bim/prop.py

@@ -341,3 +341,4 @@ class BIMMeshProperties(PropertyGroup):
     is_parametric: BoolProperty(name="Is Parametric", default=False)
     ifc_definition: StringProperty(name="IFC Definition")
     ifc_parameters: CollectionProperty(name="IFC Parameters", type=IfcParameter)
+    material_checksum: StringProperty(name="Material Checksum")

src/blenderbim/blenderbim/core/geometry.py

@@ -62,6 +62,7 @@ def add_representation(
             styles=geometry.get_styles(obj),
             should_use_presentation_style_assignment=geometry.should_use_presentation_style_assignment(),
         )
+        geometry.record_object_materials(obj)
 
     ifc.run("geometry.assign_representation", product=element, representation=representation)
 

src/blenderbim/blenderbim/core/tool.py

@@ -100,6 +100,7 @@ class Geometry:
     def is_mapped_representation(cls, representation): pass
     def is_type_product(cls, element): pass
     def link(cls, element, obj): pass
+    def record_object_materials(cls, obj): pass
     def record_object_position(cls, obj): pass
     def rename_object(cls, obj, name): pass
     def replace_object_with_empty(cls, obj): pass

src/blenderbim/blenderbim/tool/geometry.py

@@ -224,6 +224,10 @@ class Geometry(blenderbim.core.tool.Geometry):
     def link(cls, element, obj):
         obj.BIMMeshProperties.ifc_definition_id = element.id()
 
+    @classmethod
+    def record_object_materials(cls, obj):
+        obj.data.BIMMeshProperties.material_checksum = str([s.id() for s in cls.get_styles(obj) if s])
+
     @classmethod
     def record_object_position(cls, obj):
         # These are recorded separately because they have different numerical tolerances

src/blenderbim/test/bim/feature/project.feature

@@ -401,3 +401,18 @@ Scenario: Export IFC - with changed style colour synchronised
     And an empty Blender session is started
     And I press "bim.load_project(filepath='{cwd}/test/files/export.ifc')"
     Then the material "Material" colour is "1,0,0,1"
+
+Scenario: Export IFC - with changed style element synchronised
+    Given an empty IFC project
+    And I add a cube
+    And the object "Cube" is selected
+    And I add a material
+    And I set "scene.BIMRootProperties.ifc_class" to "IfcWall"
+    And I press "bim.assign_class"
+    And the object "IfcWall/Cube" is selected
+    When I add a material
+    And the material "Material.001" colour is set to "1,0,0,1"
+    And I press "export_ifc.bim(filepath='{cwd}/test/files/export.ifc')"
+    And an empty Blender session is started
+    And I press "bim.load_project(filepath='{cwd}/test/files/export.ifc')"
+    Then the material "Material.001" colour is "1,0,0,1"

src/blenderbim/test/bim/test_feature.py

@@ -91,6 +91,7 @@ def i_add_a_sun():
 
 
 @given("I add a material")
+@when("I add a material")
 def i_add_a_material():
     bpy.context.active_object.active_material = bpy.data.materials.new("Material")
 

src/blenderbim/test/core/test_geometry.py

@@ -74,6 +74,7 @@ class TestAddRepresentation:
             styles=["style"],
             should_use_presentation_style_assignment=False,
         ).should_be_called()
+        geometry.record_object_materials("obj").should_be_called()
 
         # Assign representation to product
         ifc.run("geometry.assign_representation", product="element", representation="representation").should_be_called()

src/blenderbim/test/tool/test_geometry.py

@@ -352,6 +352,19 @@ class TestLink(NewFile):
         assert obj.BIMMeshProperties.ifc_definition_id == element.id()
 
 
+class TestRecordObjectMaterials(NewFile):
+    def test_run(self):
+        obj = bpy.data.objects.new("Object", bpy.data.meshes.new("Mesh"))
+        ifc = ifcopenshell.file()
+        tool.Ifc.set(ifc)
+        style = ifc.createIfcSurfaceStyle()
+        material = bpy.data.materials.new("Material")
+        material.BIMMaterialProperties.ifc_style_id = style.id()
+        obj.data.materials.append(material)
+        subject.record_object_materials(obj)
+        assert obj.data.BIMMeshProperties.material_checksum == str([style.id()])
+
+
 class TestRecordObjectPosition(NewFile):
     def test_run(self):
         obj = bpy.data.objects.new("Object", None)