Alignment API update for station and positioning referents. Fixes bug with fallback position.

src/ifcopenshell-python/test/api/alignment/test_add_positioning_referent.py

@@ -0,0 +1,100 @@
+# IfcOpenShell - IFC toolkit and geometry engine
+# Copyright (C) 2025 Thomas Krijnen <thomas@aecgeeks.com>
+#
+# This file is part of IfcOpenShell.
+#
+# IfcOpenShell is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Lesser General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# IfcOpenShell is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public License
+# along with IfcOpenShell.  If not, see <http://www.gnu.org/licenses/>.
+
+
+import ifcopenshell.api.alignment
+import ifcopenshell.api.context
+import ifcopenshell.api.unit
+import ifcopenshell.util.element
+
+
+def test_add_positioning_referent():
+    file = ifcopenshell.file(schema="IFC4X3")
+    project = file.createIfcProject(GlobalId=ifcopenshell.guid.new(), Name="Test")
+    length = ifcopenshell.api.unit.add_si_unit(file, unit_type="LENGTHUNIT")
+    ifcopenshell.api.unit.assign_unit(file, units=[length])
+    geometric_representation_context = ifcopenshell.api.context.add_context(file, context_type="Model")
+    axis_model_representation_subcontext = ifcopenshell.api.context.add_context(
+        file,
+        context_type="Model",
+        context_identifier="Axis",
+        target_view="MODEL_VIEW",
+        parent=geometric_representation_context,
+    )
+
+    alignment = ifcopenshell.api.alignment.create(file, "TestAlignment", start_station=2000.0)
+
+    horizontal_layout = ifcopenshell.api.alignment.get_horizontal_layout(alignment)
+    segment = ifcopenshell.api.alignment.get_layout_segments(horizontal_layout)[0]
+
+    referent = ifcopenshell.api.alignment.add_positioning_referent(
+        file, "P.C.", alignment, distance_along=0.0, station=2000.0, positioned_product=segment
+    )
+
+    assert referent.is_a("IfcReferent")
+    assert referent.PredefinedType == "POSITION"
+    assert referent.Name == "P.C."
+    assert ifcopenshell.util.element.get_pset(element=referent, name="Pset_Stationing")
+    assert ifcopenshell.util.element.get_pset(element=referent, name="Pset_Stationing", prop="Station") == 2000.0
+    assert referent.ObjectPlacement != None
+
+    assert len(referent.Positions) == 1
+    rel_positions = referent.Positions[0]
+    assert rel_positions.is_a("IfcRelPositions")
+    assert rel_positions.RelatingPositioningElement == referent
+    assert rel_positions.RelatedProducts == (segment,)
+
+
+def test_add_positioning_referent_creates_separate_referent_per_call():
+    file = ifcopenshell.file(schema="IFC4X3")
+    project = file.createIfcProject(GlobalId=ifcopenshell.guid.new(), Name="Test")
+    length = ifcopenshell.api.unit.add_si_unit(file, unit_type="LENGTHUNIT")
+    ifcopenshell.api.unit.assign_unit(file, units=[length])
+    geometric_representation_context = ifcopenshell.api.context.add_context(file, context_type="Model")
+    axis_model_representation_subcontext = ifcopenshell.api.context.add_context(
+        file,
+        context_type="Model",
+        context_identifier="Axis",
+        target_view="MODEL_VIEW",
+        parent=geometric_representation_context,
+    )
+
+    alignment = ifcopenshell.api.alignment.create(file, "TestAlignment", start_station=2000.0)
+
+    horizontal_layout = ifcopenshell.api.alignment.get_horizontal_layout(alignment)
+    segment = ifcopenshell.api.alignment.get_layout_segments(horizontal_layout)[0]
+
+    first_referent = ifcopenshell.api.alignment.add_positioning_referent(
+        file, "P.C.", alignment, distance_along=0.0, station=2000.0, positioned_product=segment
+    )
+
+    other_product = file.createIfcBuildingElementProxy(GlobalId=ifcopenshell.guid.new(), Name="Sign")
+    second_referent = ifcopenshell.api.alignment.add_positioning_referent(
+        file, "P.C.", alignment, distance_along=0.0, station=2000.0, positioned_product=other_product
+    )
+
+    # each call creates its own IfcReferent, each with its own IfcRelPositions to the product passed in
+    assert first_referent != second_referent
+    assert len(first_referent.Positions) == 1
+    assert first_referent.Positions[0].RelatedProducts == (segment,)
+    assert len(second_referent.Positions) == 1
+    assert second_referent.Positions[0].RelatedProducts == (other_product,)
+
+
+test_add_positioning_referent()
+test_add_positioning_referent_creates_separate_referent_per_call()

src/ifcopenshell-python/test/api/alignment/test_add_stationing_to_alignment.py

@@ -48,5 +48,26 @@ def test_add_stationing_to_alignment():
     assert ifcopenshell.util.element.get_pset(element=referent, name="Pset_Stationing", prop="Station") == 2000.0
     assert referent.ObjectPlacement != None
 
+    # add a station equation at 1000 distance along. this is station 3+000 in coming and 4+000 outgoing.
+    # this is a gap equation.
+    second_referent = ifcopenshell.api.alignment.add_stationing_referent(
+        file, "4+000.000", alignment, distance_along=1000.0, station=4000.0, incoming_station=3000.0
+    )
+
+    referent_nest = ifcopenshell.api.alignment.get_referent_nest(file, alignment)
+    assert len(referent_nest.RelatedObjects) == 2
+
+    assert second_referent == referent_nest.RelatedObjects[1]
+
+    assert second_referent.PredefinedType == "STATION"
+    assert second_referent.Name == "4+000.000"
+    assert ifcopenshell.util.element.get_pset(element=second_referent, name="Pset_Stationing")
+    assert ifcopenshell.util.element.get_pset(element=second_referent, name="Pset_Stationing", prop="Station") == 4000.0
+    assert (
+        ifcopenshell.util.element.get_pset(element=second_referent, name="Pset_Stationing", prop="IncomingStation")
+        == 3000.0
+    )
+    assert second_referent.ObjectPlacement != None
+
 
 test_add_stationing_to_alignment()

src/ifcopenshell-python/test/api/alignment/test_distance_along_from_station.py

@@ -53,4 +53,56 @@ def test_distance_along_from_station():
     assert ifcopenshell.api.alignment.distance_along_from_station(file, alignment, 17525.36) == pytest.approx(7525.36)
 
 
+def test_distance_along_from_station_with_station_equations():
+    # Reproduces the worked example from the IFC Alignment Geometry Implementation Guide, chapter 9.2.6:
+    # a gap equation (P3: incoming 14+00.00, outgoing 17+00.00) and an overlap equation
+    # (P4: incoming 19+00.00, outgoing 18+50.00).
+    file = ifcopenshell.file(schema="IFC4X3")
+    project = file.createIfcProject(GlobalId=ifcopenshell.guid.new(), Name="Test")
+    length = ifcopenshell.api.unit.add_conversion_based_unit(file, name="foot")
+    ifcopenshell.api.unit.assign_unit(file, units=[length])
+    geometric_representation_context = ifcopenshell.api.context.add_context(file, context_type="Model")
+    axis_model_representation_subcontext = ifcopenshell.api.context.add_context(
+        file,
+        context_type="Model",
+        context_identifier="Axis",
+        target_view="MODEL_VIEW",
+        parent=geometric_representation_context,
+    )
+
+    coordinates = [(500.0, 2500.0), (3340.0, 660.0), (4340.0, 5000.0), (7600.0, 4560.0), (8480.0, 2010.0)]
+    radii = [(1000.0), (1250.0), (950.0)]
+    vpoints = [(0.0, 100.0), (2000.0, 135.0), (5000.0, 105.0), (7400.0, 153.0), (9800.0, 105.0), (12800.0, 90.0)]
+    lengths = [(1600.0), (1200.0), (2000.0), (800.0)]
+
+    alignment = ifcopenshell.api.alignment.create_by_pi_method(
+        file, "TestAlignment", coordinates, radii, vpoints, lengths, start_station=1000.0
+    )
+
+    ifcopenshell.api.alignment.add_stationing_referent(
+        file, "P3", alignment, distance_along=400.0, station=1700.0, incoming_station=1400.0
+    )
+    ifcopenshell.api.alignment.add_stationing_referent(
+        file, "P4", alignment, distance_along=600.0, station=1850.0, incoming_station=1900.0
+    )
+
+    distance_along_from_station = ifcopenshell.api.alignment.distance_along_from_station
+
+    # between P2 and P3: Sta. 13+00.00
+    assert distance_along_from_station(file, alignment, 1300.0) == pytest.approx(300.0)
+
+    # between P3 and P4: Sta. 18+00.00
+    assert distance_along_from_station(file, alignment, 1800.0) == pytest.approx(500.0)
+
+    # between P4 and P5: Sta. 19+25.00
+    assert distance_along_from_station(file, alignment, 1925.0) == pytest.approx(675.0)
+
+    # Sta. 15+00.00 falls inside the gap opened by the equation at P3 and has no corresponding distance along
+    assert distance_along_from_station(file, alignment, 1500.0) is None
+
+    # Sta. 18+75.00 falls inside the overlap zone at P4; the post-equation (outgoing) match is returned
+    assert distance_along_from_station(file, alignment, 1875.0) == pytest.approx(625.0)
+
+
 test_distance_along_from_station()
+test_distance_along_from_station_with_station_equations()