When updating representations, the existing representation type is prioritised unless you tell it otherwise. See #1748.

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

@@ -200,6 +200,9 @@ class UpdateRepresentation(bpy.types.Operator):
                 )
             )
 
+        if not self.ifc_representation_class:
+            self.ifc_representation_class = self.auto_detect_ifc_representation_class(product, old_representation) or ""
+
         representation_data = {
             "context": context_of_items,
             "blender_object": obj,
@@ -245,6 +248,25 @@ class UpdateRepresentation(bpy.types.Operator):
         if obj.data.BIMMeshProperties.ifc_parameters:
             bpy.ops.bim.get_representation_ifc_parameters()
 
+    def auto_detect_ifc_representation_class(self, element, representation):
+        material = ifcopenshell.util.element.get_material(element)
+
+        if material.is_a("IfcMaterialProfileSetUsage"):
+            return "IfcExtrudedAreaSolid/IfcMaterialProfileSetUsage"
+
+        extruded_areas = [e for e in self.file.traverse(representation) if e.is_a() == "IfcExtrudedAreaSolid"]
+
+        if len(extruded_areas) != 1:
+            return None  # It's too complex for us to derive topologically right now
+
+        profile_def = extruded_areas[0].SweptArea
+
+        if profile_def.is_a() == "IfcRectangleProfileDef":
+            return "IfcExtrudedAreaSolid/IfcRectangleProfileDef"
+        elif profile_def.is_a() == "IfcCircleProfileDef":
+            return "IfcExtrudedAreaSolid/IfcCircleProfileDef"
+        return "IfcExtrudedAreaSolid/IfcArbitraryProfileDefWithVoids"
+
 
 class UpdateParametricRepresentation(bpy.types.Operator):
     bl_idname = "bim.update_parametric_representation"

src/blenderbim/blenderbim/bim/module/geometry/ui.py

@@ -109,6 +109,10 @@ class BIM_PT_mesh(Panel):
         row = layout.row()
         row.operator("bim.update_representation")
 
+        row = layout.row()
+        op = row.operator("bim.update_representation", text="Update Mesh As Tessellation")
+        op.ifc_representation_class = "IfcTessellatedFaceSet"
+
         row = layout.row()
         op = row.operator("bim.update_representation", text="Update Mesh As Rectangle Extrusion")
         op.ifc_representation_class = "IfcExtrudedAreaSolid/IfcRectangleProfileDef"

src/blenderbim/blenderbim/tool/geometry.py

@@ -102,6 +102,7 @@ class Geometry(blenderbim.core.tool.Geometry):
         ifc_import_settings = blenderbim.bim.import_ifc.IfcImportSettings.factory(bpy.context, None, logger)
         element = tool.Ifc.get_entity(obj)
         settings = ifcopenshell.geom.settings()
+        settings.set(settings.WELD_VERTICES, True)
 
         if representation.ContextOfItems.ContextIdentifier == "Body":
             if element.is_a("IfcTypeProduct") or enable_dynamic_voids: