Fix #2823. Only update colours if you actually change them.

src/blenderbim/blenderbim/bim/export_ifc.py

@@ -126,7 +126,8 @@ class IfcExporter:
                 continue
             try:
                 if isinstance(obj, bpy.types.Material):
-                    blenderbim.core.style.update_style_colours(tool.Ifc, tool.Style, obj=obj)
+                    if self.has_changed_shading(obj):
+                        blenderbim.core.style.update_style_colours(tool.Ifc, tool.Style, obj=obj)
                 else:
                     element = tool.Ifc.get_entity(obj)
                     if element:
@@ -148,6 +149,10 @@ class IfcExporter:
         checksum = obj.data.BIMMeshProperties.material_checksum
         return checksum != str([s.id() for s in tool.Geometry.get_styles(obj) if s])
 
+    def has_changed_shading(self, obj):
+        checksum = obj.BIMMaterialProperties.shading_checksum
+        return checksum != repr(np.array(obj.diffuse_color).tobytes())
+
     def sync_object_placement(self, obj):
         if not tool.Ifc.is_moved(obj):
             return

src/blenderbim/blenderbim/bim/import_ifc.py

@@ -1534,6 +1534,8 @@ class IfcImporter:
         if rendering_style and texture_style:
             self.create_surface_style_with_textures(blender_material, rendering_style, texture_style)
 
+        tool.Style.record_shading(blender_material)
+
     def create_surface_style_shading(self, blender_material, surface_style):
         alpha = 1.0
         # Transparency was added in IFC4

src/blenderbim/blenderbim/bim/prop.py

@@ -412,6 +412,7 @@ class BIMMaterialProperties(PropertyGroup):
     attributes: CollectionProperty(name="Attributes", type=Attribute)
     # In Blender, a material object can map to an IFC material, IFC surface style, or both
     ifc_style_id: IntProperty(name="IFC Style ID")
+    shading_checksum: StringProperty(name="Shading Checksum")
 
 
 class BIMMeshProperties(PropertyGroup):

src/blenderbim/blenderbim/core/style.py

@@ -63,6 +63,8 @@ def update_style_colours(ifc, style, obj=None):
         else:
             ifc.run("style.add_surface_style", style=element, ifc_class="IfcSurfaceStyleShading", attributes=attributes)
 
+    style.record_shading(obj)
+
 
 def update_style_textures(ifc, style, obj=None, representation=None):
     element = style.get_style(obj)

src/blenderbim/blenderbim/core/tool.py

@@ -719,6 +719,7 @@ class Style:
     def import_presentation_styles(cls, style_type): pass
     def import_surface_attributes(cls, style, obj): pass
     def is_editing_styles(cls): pass
+    def record_shading(cls, obj): pass
     def select_elements(cls, elements): pass
 
 

src/blenderbim/blenderbim/tool/style.py

@@ -17,6 +17,7 @@
 # along with BlenderBIM Add-on.  If not, see <http://www.gnu.org/licenses/>.
 
 import bpy
+import numpy as np
 import ifcopenshell
 import blenderbim.core.tool
 import blenderbim.tool as tool
@@ -203,6 +204,10 @@ class Style(blenderbim.core.tool.Style):
     def is_editing_styles(cls):
         return bpy.context.scene.BIMStylesProperties.is_editing
 
+    @classmethod
+    def record_shading(cls, obj):
+        obj.BIMMaterialProperties.shading_checksum = repr(np.array(obj.diffuse_color).tobytes())
+
     @classmethod
     def select_elements(cls, elements):
         for element in elements:

src/blenderbim/test/core/test_style.py

@@ -88,6 +88,7 @@ class TestUpdateStyleColours:
         style.get_surface_rendering_style("obj").should_be_called().will_return("style")
         style.get_surface_rendering_attributes("obj").should_be_called().will_return("attributes")
         ifc.run("style.edit_surface_style", style="style", attributes="attributes").should_be_called()
+        style.record_shading("obj").should_be_called()
         subject.update_style_colours(ifc, style, obj="obj")
 
     def test_adding_a_rendering_style_if_not_available(self, ifc, style):
@@ -98,6 +99,7 @@ class TestUpdateStyleColours:
         ifc.run(
             "style.add_surface_style", style="element", ifc_class="IfcSurfaceStyleRendering", attributes="attributes"
         ).should_be_called()
+        style.record_shading("obj").should_be_called()
         subject.update_style_colours(ifc, style, obj="obj")
 
     def test_updating_shading_style_as_a_fallback_if_available(self, ifc, style):
@@ -106,6 +108,7 @@ class TestUpdateStyleColours:
         style.get_surface_shading_style("obj").should_be_called().will_return("style")
         style.get_surface_shading_attributes("obj").should_be_called().will_return("attributes")
         ifc.run("style.edit_surface_style", style="style", attributes="attributes").should_be_called()
+        style.record_shading("obj").should_be_called()
         subject.update_style_colours(ifc, style, obj="obj")
 
     def test_adding_a_shading_style_as_a_fallback_if_not_available(self, ifc, style):
@@ -116,6 +119,7 @@ class TestUpdateStyleColours:
         ifc.run(
             "style.add_surface_style", style="element", ifc_class="IfcSurfaceStyleShading", attributes="attributes"
         ).should_be_called()
+        style.record_shading("obj").should_be_called()
         subject.update_style_colours(ifc, style, obj="obj")