Improve QTO of segment lengths

Previous method uses bounding box which could be wrong if the app (Revit) doesn't extrude in +Z and has a slope (e.g. most pipes). Also Revit tends to use rectangle profiles not for the cross section, but instead for the footprint which is crazy.

src/ifc5d/ifc5d/IFC4QtoBaseQuantities.json

@@ -97,7 +97,7 @@
                 "Qto_CableCarrierSegmentBaseQuantities": {
                     "CrossSectionArea": null,
                     "GrossWeight": null,
-                    "Length": "net_get_max_xyz",
+                    "Length": "net_get_segment_length",
                     "OuterSurfaceArea": null
                 }
             },
@@ -110,7 +110,7 @@
                 "Qto_CableSegmentBaseQuantities": {
                     "CrossSectionArea": null,
                     "GrossWeight": null,
-                    "Length": "net_get_max_xyz",
+                    "Length": "net_get_segment_length",
                     "OuterSurfaceArea": null
                 }
             },
@@ -236,7 +236,7 @@
                 "Qto_DuctSegmentBaseQuantities": {
                     "GrossCrossSectionArea": null,
                     "GrossWeight": null,
-                    "Length": "net_get_max_xyz",
+                    "Length": "net_get_segment_length",
                     "NetCrossSectionArea": null,
                     "OuterSurfaceArea": null
                 }
@@ -421,7 +421,7 @@
                 "Qto_PipeSegmentBaseQuantities": {
                     "GrossCrossSectionArea": null,
                     "GrossWeight": null,
-                    "Length": "net_get_max_xyz",
+                    "Length": "net_get_segment_length",
                     "NetCrossSectionArea": null,
                     "NetWeight": null,
                     "OuterSurfaceArea": null

src/ifc5d/ifc5d/qto.py

@@ -21,9 +21,10 @@ import json
 import ifcopenshell
 import ifcopenshell.api
 import ifcopenshell.api.pset
-import ifcopenshell.util.element
 import ifcopenshell.util.unit
+import ifcopenshell.util.element
 import ifcopenshell.util.selector
+import ifcopenshell.util.representation
 import multiprocessing
 from collections import namedtuple
 from typing import Any
@@ -106,6 +107,7 @@ class IfcOpenShell:
             "Footprint Perimeter",
             "The perimeter if the object's faces were projected along the Z-axis and seen top down",
         ),
+        "get_segment_length": Function("IfcLengthMeasure", "Segment Length", "Intelligently guesses the length of flow segments"),
         # IfcAreaMeasure
         "get_area": Function("IfcAreaMeasure", "Area", "The total surface area of the element"),
         "get_footprint_area": Function(
@@ -137,8 +139,9 @@ class IfcOpenShell:
         functions[f"gross_{k}"] = Function(v.measure, f"Gross {v.name}", v.description)
         functions[f"net_{k}"] = Function(v.measure, f"Net {v.name}", v.description)
 
-    @staticmethod
+    @classmethod
     def calculate(
+        cls,
         ifc_file: ifcopenshell.file,
         elements: set[ifcopenshell.entity_instance],
         qtos: dict,
@@ -150,9 +153,10 @@ class IfcOpenShell:
 
         formula_functions = {}
 
-        gross_settings = ifcopenshell.geom.settings()
+        cls.gross_settings = ifcopenshell.geom.settings()
-        gross_settings.set("disable-opening-subtractions", True)
+        cls.gross_settings.set("disable-opening-subtractions", True)
-        net_settings = ifcopenshell.geom.settings()
+        cls.net_settings = ifcopenshell.geom.settings()
+        cls.unit_scale = ifcopenshell.util.unit.calculate_unit_scale(ifc_file)
 
         gross_qtos = {}
         net_qtos = {}
@@ -161,24 +165,27 @@ class IfcOpenShell:
             for quantity, formula in quantities.items():
                 if not formula:
                     continue
-                if formula.startswith("gross_"):
+                gross_or_net_qtos = gross_qtos if formula.startswith("gross_") else net_qtos
-                    formula = formula[6:]
+                if formula.endswith("get_segment_length"):
-                    gross_qtos.setdefault(name, {})[quantity] = formula
+                    gross_or_net_qtos.setdefault(name, {})[quantity] = formula.partition("_")[2]
+                elif formula.startswith("gross_"):
+                    formula = formula.partition("_")[2]
+                    gross_or_net_qtos.setdefault(name, {})[quantity] = formula
                     formula_functions[formula] = getattr(ifcopenshell.util.shape, formula)
                 elif formula.startswith("net_"):
-                    formula = formula[4:]
+                    formula = formula.partition("_")[2]
-                    net_qtos.setdefault(name, {})[quantity] = formula
+                    gross_or_net_qtos.setdefault(name, {})[quantity] = formula
                     formula_functions[formula] = getattr(ifcopenshell.util.shape, formula)
 
         tasks = []
 
         if gross_qtos:
-            tasks.append((IfcOpenShell.create_iterator(ifc_file, gross_settings, list(elements)), gross_qtos))
+            tasks.append((IfcOpenShell.create_iterator(ifc_file, cls.gross_settings, list(elements)), gross_qtos))
 
         if net_qtos:
-            tasks.append((IfcOpenShell.create_iterator(ifc_file, net_settings, list(elements)), net_qtos))
+            tasks.append((IfcOpenShell.create_iterator(ifc_file, cls.net_settings, list(elements)), net_qtos))
 
-        unit_converter = SI2ProjectUnitConverter(ifc_file)
+        cls.unit_converter = SI2ProjectUnitConverter(ifc_file)
 
         for iterator, qtos in tasks:
             if iterator.initialize():
@@ -189,9 +196,13 @@ class IfcOpenShell:
                     for name, quantities in qtos.items():
                         results[element].setdefault(name, {})
                         for quantity, formula in quantities.items():
-                            results[element][name][quantity] = unit_converter.convert(
+                            if formula == "get_segment_length":
-                                formula_functions[formula](shape.geometry), IfcOpenShell.raw_functions[formula].measure
+                                results[element][name][quantity] = cls.get_segment_length(ifc_file, shape)
-                            )
+                            else:
+                                results[element][name][quantity] = cls.unit_converter.convert(
+                                    formula_functions[formula](shape.geometry),
+                                    IfcOpenShell.raw_functions[formula].measure,
+                                )
                     if not iterator.next():
                         break
 
@@ -201,6 +212,31 @@ class IfcOpenShell:
     ) -> ifcopenshell.geom.iterator:
         return ifcopenshell.geom.iterator(settings, ifc_file, multiprocessing.cpu_count(), include=elements)
 
+    @classmethod
+    def get_segment_length(cls, ifc_file: ifcopenshell.file, shape) -> float:
+        element = ifc_file.by_id(shape.id)
+        rep = ifcopenshell.util.representation.get_representation(element, "Model", "Body", "MODEL_VIEW")
+        if rep and len(rep.Items or []) == 1 and rep.Items[0].is_a("IfcExtrudedAreaSolid"):
+            item = rep.Items[0]
+            if item.SweptArea.is_a("IfcRectangleProfileDef"):
+                # Revit doesn't follow the +Z extrusion rule, so the rectangle isn't the cross section
+                x = item.SweptArea.XDim
+                y = item.SweptArea.YDim
+                z = item.Depth
+                return max([x, y, z])
+            elif item.SweptArea.is_a("IfcCircleProfileDef"):
+                return item.Depth
+            elif item.SweptArea.is_a("IfcParameterizedProfileDef"):
+                return item.Depth
+            try:
+                area_shape = ifcopenshell.geom.create_shape(settings, item.SweptArea)
+            except:
+                return
+            x = ifcopenshell.util.shape.get_x(area_shape.geometry) / cls.unit_scale
+            y = ifcopenshell.util.shape.get_y(area_shape.geometry) / cls.unit_scale
+            z = item.Depth
+            return max([x, y, z])
+
 
 class Blender:
     """Calculates geometry based on currently loaded Blender objects."""