Linking in models now considers multiple project norths and federates it properly

src/blenderbim/blenderbim/bim/module/georeference/prop.py

@@ -113,18 +113,32 @@ class BIMGeoreferenceProperties(PropertyGroup):
     x_axis_abscissa: StringProperty(name="X Axis Abscissa", update=update_grid_north_vector)
     x_axis_ordinate: StringProperty(name="X Axis Ordinate", update=update_grid_north_vector)
     x_axis_is_null: BoolProperty(name="X Axis Is Null")
+
+    # These are only for reference to capture data about a host model from a linked model
+    # If you relink a model from a new host origin, we can autodetect it in theory with this
     host_model_origin: StringProperty(name="Host Model Origin")
+    host_model_project_north: StringProperty(name="Host Model Angle to Grid North")
+
+    # These are only for reference, calculated using tool.Loader.calculate_model_origin
     model_origin: StringProperty(name="Model Origin")
+    model_project_north: StringProperty(name="Model Angle to Grid North")
+
+    # True if there is a temporary Blender session coordinate system
     has_blender_offset: BoolProperty(name="Has Blender Offset")
+
+    # These E, N, H, and project north are the absolute map coordinates of the Blender session
     blender_eastings: StringProperty(name="Blender Eastings", default="0")
     blender_northings: StringProperty(name="Blender Northings", default="0")
     blender_orthogonal_height: StringProperty(name="Blender Orthogonal Height", default="0")
     blender_project_north: StringProperty(name="Blender Angle to Grid North", default="0")
+
+    # These are the helmert transformation parameters of the Blender session
     blender_offset_x: StringProperty(name="Blender Offset X", default="0")
     blender_offset_y: StringProperty(name="Blender Offset Y", default="0")
     blender_offset_z: StringProperty(name="Blender Offset Z", default="0")
     blender_x_axis_abscissa: StringProperty(name="Blender X Axis Abscissa", default="1")
     blender_x_axis_ordinate: StringProperty(name="Blender X Axis Ordinate", default="0")
+
     true_north_angle: StringProperty(name="True North Angle", update=update_true_north_angle)
     true_north_abscissa: StringProperty(name="True North Abscissa", update=update_true_north_vector)
     true_north_ordinate: StringProperty(name="True North Ordinate", update=update_true_north_vector)

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

@@ -1060,10 +1060,12 @@ def run():
     gprops = bpy.context.scene.BIMGeoreferenceProperties
     # Our model origin becomes their host model origin
     gprops.host_model_origin = "{gprops.model_origin}"
+    gprops.host_model_project_north = "{gprops.model_project_north}"
     gprops.has_blender_offset = {gprops.has_blender_offset}
     gprops.blender_eastings = "{gprops.blender_eastings}"
     gprops.blender_northings = "{gprops.blender_northings}"
     gprops.blender_orthogonal_height = "{gprops.blender_orthogonal_height}"
+    gprops.blender_project_north = "{gprops.blender_project_north}"
     gprops.blender_offset_x = "{gprops.blender_offset_x}"
     gprops.blender_offset_y = "{gprops.blender_offset_y}"
     gprops.blender_offset_z = "{gprops.blender_offset_z}"
@@ -1395,6 +1397,7 @@ class LoadLinkedProject(bpy.types.Operator):
         elif tool.Loader.settings.false_origin_mode == "AUTOMATIC":
             if gprops.host_model_origin:
                 tool.Loader.settings.false_origin = list(map(float, gprops.host_model_origin.split(",")))
+                tool.Loader.settings.project_north = float(gprops.host_model_project_north)
                 tool.Loader.set_manual_blender_offset(self.file)
             else:
                 tool.Loader.guess_false_origin(self.file)
@@ -1403,7 +1406,9 @@ class LoadLinkedProject(bpy.types.Operator):
         self.json_filepath = self.filepath + ".cache.json"
         data = {
             "host_model_origin": gprops.host_model_origin,
+            "host_model_project_north": gprops.host_model_project_north,
             "model_origin": gprops.model_origin,
+            "model_project_north": gprops.model_project_north,
             "has_blender_offset": gprops.has_blender_offset,
             "blender_eastings": gprops.blender_eastings,
             "blender_northings": gprops.blender_northings,

src/blenderbim/blenderbim/tool/loader.py

@@ -570,8 +570,7 @@ class Loader(blenderbim.core.tool.Loader):
         zero_origin = np.array((0, 0, 0))
         has_offset = not np.allclose(model_offset, zero_origin)
 
-        parameters = ifcopenshell.util.geolocation.get_helmert_transformation_parameters(ifc_file)
-        model_north = ifcopenshell.util.geolocation.xaxis2angle(parameters.xaa, parameters.xao)
+        model_north = ifcopenshell.util.geolocation.get_grid_north(ifc_file)
         project_north = cls.settings.project_north
         model_rotation = project_north - model_north
         if model_rotation > 180:
@@ -741,7 +740,9 @@ class Loader(blenderbim.core.tool.Loader):
             gprops.model_origin = (
                 f"{gprops.blender_eastings},{gprops.blender_northings},{gprops.blender_orthogonal_height}"
             )
+            gprops.model_project_north = gprops.blender_project_north
         else:
             gprops.model_origin = ",".join(
                 map(str, ifcopenshell.util.geolocation.auto_xyz2enh(ifc_file, 0, 0, 0))
             )
+            gprops.model_project_north = str(ifcopenshell.util.geolocation.get_grid_north(ifc_file))