Adds segment_vertices function to alignment api

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

@@ -87,6 +87,7 @@ from .layout_vertical_alignment_by_pi_method import (
     layout_vertical_alignment_by_pi_method,
 )
 from .name_segments import name_segments
+from .segment_vertices import segment_vertices
 from .update_fallback_position import update_fallback_position
 from .util import *
 
@@ -125,6 +126,7 @@ __all__ = [
     "layout_horizontal_alignment_by_pi_method",
     "layout_vertical_alignment_by_pi_method",
     "name_segments",
+    "segment_vertices",
     "register_referent_name_callback",
     "update_fallback_position",
     "get_mapped_segments",

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

@@ -0,0 +1,90 @@
+# 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 numpy as np
+
+import ifcopenshell
+import ifcopenshell.util.unit
+from ifcopenshell import entity_instance, ifcopenshell_wrapper
+
+def _intersect_lines(p1,d1,p2,d2):
+    x1,y1 = p1
+    dx1,dy1 = d1
+    x2,y2 = p2
+    dx2,dy2 = d2
+    
+    det = dx1*dy2 - dy1*dx2
+    if abs(det) < 1e-12:
+        return None # lines are parallel
+    
+    t = ((x2 - x1) * dy2 - (y2 - y1) * dx2)/det
+
+    x = x1 + t*dx1
+    y = y1 + t*dy1
+
+    return (x,y)
+
+
+def segment_vertices(file: ifcopenshell.file, curve_segment: entity_instance):
+    """
+    Genererates segment vertices. Segment vertices are the points where the tangents
+    at the start and end of the segment intersect (the PI point) and where lines
+    perpendicular to the start and end of the segment intersect (CC).
+
+    :param curve_segment: A curve segment
+    :return: tuples for Start, End, PI, CC
+    """
+    supported_segment_types = ["IFCCURVESEGMENT"]
+    segment_type = curve_segment.is_a().upper()
+    if not segment_type in supported_segment_types:
+        raise NotImplementedError(
+            f"Expected entity type to be one of {[_ for _ in supported_segment_types]}, got '{segment_type}"
+        )
+    
+    unit_scale = ifcopenshell.util.unit.calculate_unit_scale(file)
+
+    settings = ifcopenshell.geom.settings()
+    segment_fn = ifcopenshell_wrapper.map_shape(settings, curve_segment.wrapped_data)
+    segment_evaluator = ifcopenshell_wrapper.function_item_evaluator(settings, segment_fn)
+
+    s = segment_evaluator.evaluate(segment_fn.start())
+    start = np.array(s)
+    sx = float(start[0, 3]) / unit_scale
+    sy = float(start[1, 3]) / unit_scale
+    sdx = float(start[0, 0])
+    sdy = float(start[1, 0])    
+
+    e = segment_evaluator.evaluate(segment_fn.end())
+    end = np.array(e)
+    unit_scale = ifcopenshell.util.unit.calculate_unit_scale(file)
+    ex = float(end[0, 3]) / unit_scale
+    ey = float(end[1, 3]) / unit_scale
+    edx = float(end[0, 0])
+    edy = float(end[1, 0])
+
+    pi = _intersect_lines((sx,sy),(sdx,sdy),(ex,ey),(edx,edy))
+
+    sdx = float(start[0, 1])
+    sdy = float(start[1, 1])    
+    edx = float(end[0, 1])
+    edy = float(end[1, 1])
+
+    cc = _intersect_lines((sx,sy),(sdx,sdy),(ex,ey),(edx,edy))
+
+    return (sx,sy), (ex,ey), pi, cc