Fix #3414. Only clear default scene, not custom scene when loading / creating IFCs.

src/blenderbim/blenderbim/bim/handler.py

@@ -375,10 +375,6 @@ def load_post(scene):
         else:
             bpy.ops.workspace.append_activate(idname="BIM", filepath=os.path.join(cwd, "data", "workspace.blend"))
 
-        for obj in [bpy.data.objects.get("Camera"), bpy.data.objects.get("Light")]:
-            if obj:
-                bpy.data.objects.remove(obj)
-
         # To improve usability for new users, we hijack the scene properties
         # tab. We override default scene properties panels with our own poll
         # to hide them unless the user has chosen to view Blender properties.

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

@@ -48,9 +48,6 @@ class NewProject(bpy.types.Operator):
     def execute(self, context):
         bpy.ops.wm.read_homefile()
 
-        for obj in bpy.data.objects:
-            bpy.data.objects.remove(obj)
-
         if self.preset == "metric_m":
             bpy.context.scene.BIMProjectProperties.export_schema = "IFC4"
             bpy.context.scene.unit_settings.system = "METRIC"
@@ -104,6 +101,9 @@ class CreateProject(bpy.types.Operator):
         props = context.scene.BIMProjectProperties
         template = None if props.template_file == "0" else props.template_file
         blenderbim.bim.schema.reload(props.export_schema)
+        if tool.Blender.is_default_scene():
+            for obj in bpy.data.objects:
+                bpy.data.objects.remove(obj)
         core.create_project(tool.Ifc, tool.Project, schema=props.export_schema, template=template)
 
     def rollback(self, data):
@@ -591,8 +591,9 @@ class LoadProject(bpy.types.Operator, IFCFileSelector):
         if self.should_start_fresh_session:
             bpy.ops.wm.read_homefile()
 
-            for obj in bpy.data.objects:
-                bpy.data.objects.remove(obj)
+            if tool.Blender.is_default_scene():
+                for obj in bpy.data.objects:
+                    bpy.data.objects.remove(obj)
 
         context.window_manager.fileselect_add(self)
         return {"RUNNING_MODAL"}

src/blenderbim/blenderbim/tool/blender.py

@@ -57,6 +57,14 @@ class Blender:
         area_index = screen_areas.index(current_area)
         return context.screen.BIMAreaProperties[area_index].tab == tab
 
+    @classmethod
+    def is_default_scene(cls):
+        if len(bpy.context.scene.objects) != 3:
+            return False
+        if {obj.type for obj in bpy.context.scene.objects} == {"MESH", "LIGHT", "CAMERA"}:
+            return True
+        return False
+
     @classmethod
     def get_name(cls, ifc_class, name):
         if not bpy.data.objects.get(f"{ifc_class}/{name}"):