get distance along alignment from station

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

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