get distance along alignment from station

New alignment api function to get the horizontal distance along an alignment from a station value

Author: RickBrice

src/ifcopenshell-python/ifcopenshell/api/alignment/__init__.py

@@ -51,6 +51,7 @@
 from .create_horizontal_alignment_by_pi_method import create_horizontal_alignment_by_pi_method
 from .create_geometric_representation import create_geometric_representation
 from .create_vertical_alignment_by_pi_method import create_vertical_alignment_by_pi_method
+from .distance_along_from_station import distance_along_from_station
 from .get_alignment_layouts import get_alignment_layouts
 from .get_axis_subcontext import get_axis_subcontext
 from .get_basis_curve import get_basis_curve

src/ifcopenshell-python/ifcopenshell/api/alignment/distance_along_from_station.py

@@ -0,0 +1,56 @@
+# 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
+import ifcopenshell.api.alignment
+import ifcopenshell.api.nest
+import ifcopenshell.guid
+from ifcopenshell import entity_instance
+
+
+def distance_along_from_station(file: ifcopenshell.file, alignment: entity_instance, station: float) -> float:
+    """
+    Given a station, returns the distance along the horizontal alignment.
+
+    If the alignment does not have stationing defined with an IfcReferent, the start of the alignment is assumed
+    to be at station 0.0. That is, the station is the distance along.
+
+    .. note:: The current implementation does not account for station equations and assumes stationing is increasing along the alignment.
+
+    :param alignment: the alignment
+    :param station: station value
+    :return: distance along the horizontal alignment
+
+    Example:
+
+    .. code:: python
+
+        alignment = model.by_type("IfcAlignment")[0] # alignment with start station 1+00.00
+        dist_along = ifcopenshell.api.alignment.distance_along_from_station(model,alignment=alignment,station=200.0)
+        print(dist_along) # 100.00
+    """
+
+    start_station = 0.0
+    components = ifcopenshell.util.element.get_components(alignment)
+    for c in components:
+        if c.is_a("IfcReferent") and ifcopenshell.util.element.get_predefined_type(c) == "STATION":
+            start_station = ifcopenshell.util.element.get_pset(c, name="Pset_Stationing", prop="Station")
+            break
+
+    dist_along = station - start_station
+    return dist_along

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

@@ -0,0 +1,55 @@
+# 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 pytest
+import ifcopenshell.api.alignment
+import ifcopenshell.api.context
+
+
+def test_add_stationing_to_alignment():
+    file = ifcopenshell.file(schema="IFC4X3_ADD2")
+    project = file.createIfcProject(Name="Test")
+    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_alignment_by_pi_method(
+        file, "TestAlignment", coordinates, radii, vpoints, lengths
+    )
+
+    # test alignment without stationing referent
+    assert ifcopenshell.api.alignment.distance_along_from_station(file, alignment, 500.0) == pytest.approx(500.0)
+
+    # add stationing referent
+    ifcopenshell.api.alignment.add_stationing_to_alignment(file, alignment, 10000.0)
+
+    # Station 138+83.96
+    assert ifcopenshell.api.alignment.distance_along_from_station(file, alignment, 13883.96) == pytest.approx(3883.96)
+
+    # Station 175+25.36
+    assert ifcopenshell.api.alignment.distance_along_from_station(file, alignment, 17525.36) == pytest.approx(7525.36)