You can now assign derived quantities from products to cost items

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

@@ -379,14 +379,30 @@ class AddCostItemQuantity(bpy.types.Operator):
 
     def execute(self, context):
         self.file = IfcStore.get_file()
+        self.props = context.scene.BIMCostProperties
+        if self.props.quantity_types == "QTO":
+            self.add_quantities_from_qto_filter()
+        else:
+            self.add_manual_quantity()
+        Data.load(self.file)
+        return {"FINISHED"}
+
+    def add_quantities_from_qto_filter(self):
+        ifcopenshell.api.run(
+            "cost.assign_cost_item_product_quantities",
+            self.file,
+            cost_item=self.file.by_id(self.cost_item),
+            qto_name=self.props.qto_name,
+            prop_name=self.props.prop_name
+        )
+
+    def add_manual_quantity(self):
         ifcopenshell.api.run(
             "cost.add_cost_item_quantity",
             self.file,
             cost_item=self.file.by_id(self.cost_item),
             ifc_class=self.ifc_class,
         )
-        Data.load(self.file)
-        return {"FINISHED"}
 
 
 class RemoveCostItemQuantity(bpy.types.Operator):

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

@@ -28,9 +28,13 @@ def getQuantityTypes(self, context):
     global quantitytypes_enum
     if len(quantitytypes_enum) == 0 and IfcStore.get_schema():
         quantitytypes_enum.clear()
-        quantitytypes_enum = [
-            (t.name(), t.name(), "") for t in IfcStore.get_schema().declaration_by_name("IfcPhysicalSimpleQuantity").subtypes()
-        ]
+        quantitytypes_enum = [("QTO", "Qto", "Derive quantities from IFC quantity sets")]
+        quantitytypes_enum.extend(
+            [
+                (t.name(), t.name(), "")
+                for t in IfcStore.get_schema().declaration_by_name("IfcPhysicalSimpleQuantity").subtypes()
+            ]
+        )
     return quantitytypes_enum
 
 
@@ -69,13 +73,18 @@ class BIMCostProperties(PropertyGroup):
     cost_item_attributes: CollectionProperty(name="Task Attributes", type=Attribute)
     contracted_cost_items: StringProperty(name="Contracted Cost Items", default="[]")
     quantity_types: EnumProperty(items=getQuantityTypes, name="Quantity Types")
+    qto_name: StringProperty(name="Qto Name")
+    prop_name: StringProperty(name="Prop Name")
     active_cost_item_quantity_id: IntProperty(name="Active Cost Item Quantity Id")
     quantity_attributes: CollectionProperty(name="Quantity Attributes", type=Attribute)
-    cost_types: EnumProperty(items=[
-        ("FIXED", "Fixed", "The cost value is a fixed number"),
-        ("SUM", "Sum", "The cost value is automatically derived from the sum of all nested cost items"),
-        ("CATEGORY", "Category", "The cost value represents a single category"),
-    ], name="Cost Types")
+    cost_types: EnumProperty(
+        items=[
+            ("FIXED", "Fixed", "The cost value is a fixed number"),
+            ("SUM", "Sum", "The cost value is automatically derived from the sum of all nested cost items"),
+            ("CATEGORY", "Category", "The cost value represents a single category"),
+        ],
+        name="Cost Types",
+    )
     cost_category: StringProperty(name="Cost Category")
     active_cost_item_value_id: IntProperty(name="Active Cost Item Value Id")
     cost_value_attributes: CollectionProperty(name="Cost Value Attributes", type=Attribute)

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

@@ -96,6 +96,9 @@ class BIM_PT_cost_schedules(Panel):
     def draw_editable_cost_item_quantities_ui(self):
         row = self.layout.row(align=True)
         row.prop(self.props, "quantity_types", text="")
+        if self.props.quantity_types == "QTO":
+            row.prop(self.props, "qto_name", text="")
+            row.prop(self.props, "prop_name", text="")
         op = row.operator("bim.add_cost_item_quantity", text="", icon="ADD")
         op.cost_item = self.props.active_cost_item_id
         op.ifc_class = self.props.quantity_types

src/ifcopenshell-python/ifcopenshell/api/cost/assign_cost_item_product_quantities.py

@@ -0,0 +1,32 @@
+import ifcopenshell.api
+
+
+class Usecase:
+    def __init__(self, file, **settings):
+        self.file = file
+        self.settings = {"cost_item": None, "qto_name": "", "prop_name": ""}
+        for key, value in settings.items():
+            self.settings[key] = value
+
+    def execute(self):
+        self.quantities = set(self.settings["cost_item"].CostQuantities or [])
+        for control in self.settings["cost_item"].Controls or []:
+            for related_object in control.RelatedObjects:
+                self.add_quantity_from_related_object(related_object)
+        self.settings["cost_item"].CostQuantities = list(self.quantities)
+
+    def add_quantity_from_related_object(self, element):
+        if element.is_a("IfcTypeObject"):
+            for definition in element.HasPropertySets or []:
+                self.add_quantity_from_qto(definition)
+        else:
+            for relationship in element.IsDefinedBy:
+                if relationship.is_a("IfcRelDefinesByProperties"):
+                    self.add_quantity_from_qto(relationship.RelatingPropertyDefinition)
+
+    def add_quantity_from_qto(self, qto):
+        if not qto.is_a("IfcElementQuantity") or qto.Name.lower() != self.settings["qto_name"].lower():
+            return
+        for prop in qto.Quantities:
+            if prop.is_a("IfcPhysicalSimpleQuantity") and prop.Name.lower() == self.settings["prop_name"].lower():
+                self.quantities.add(prop)