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

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

@@ -0,0 +1,87 @@
+# 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
+import ifcopenshell.api.unit
+
+
+def test_segment_vertices():
+    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,
+    )
+
+    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
+    )
+
+    # test the horizontal alignment geometry segments
+    expect = [[(500.0, 2500.0), (2142.2379952109395, 1436.01482000418), None, None],
+              [(2142.2379952109395, 1436.01482000418), (3660.446122847804, 2050.7361731594674), (3340.0, 659.9999999999998), (2685.9792975637306, 2275.267699722618)],
+              [(3660.4461228478035, 2050.7361731594674), (4084.115884236641, 3889.4629375870213), None, None],
+              [(4084.115884236641, 3889.4629375870218), (5469.395067206271, 4847.5663099476205), (4340.0, 5000.000000000001), (5302.199415841732, 3608.7985293830834)],
+              [(5469.395067206271, 4847.56630994762), (7019.971366858418, 4638.286073184753), None, None],
+              [(7019.971366858417, 4638.286073184753), (7790.932128312586, 4006.7307645487535), (7600.0, 4560.0), (6892.902671821368, 3696.8225599557054)],
+              [(7790.932128312587, 4006.7307645487535), (8480.0, 2010.0000000000002), None, None],
+              [(8480.0, 2010.0000000000002), (8480.0, 2010.0000000000002), None, None]
+          ]
+    curve = ifcopenshell.api.alignment.get_basis_curve(alignment)
+    for segment,expected in zip(curve.Segments,expect):
+        s,e,pi,cc = ifcopenshell.api.alignment.segment_vertices(file,segment)
+        assert s == pytest.approx(expected[0])
+        assert e == pytest.approx(expected[1])
+        assert pi == pytest.approx(expected[2])
+        assert cc == pytest.approx(expected[3])
+
+
+    # test vertical curve segments
+    expect = [[(0.0, 100.0), (1200.0, 121.0), None, None],
+              [(1200.0, 121.0), (2799.99999384661, 127.00000006153391), (1999.9999969233054, 134.99999994615786), (2218.1436363635016, -58058.63636362867)],
+              [(2800.0, 127.0), (4400.0, 111.0), None, None],
+              [(4400.0, 111.0), (5599.999994508736, 116.9999998901747), (4999.999997254367, 105.00000002745632), (4800.039999999177, 40114.99999991764)],
+              [(5600.0, 117.0), (6400.0, 133.0), None, None],
+              [(6400.0, 133.0), (8399.999995932576, 133.0000000813485), (7399.999997966288, 152.99999995932575), (7399.999999999187, -49866.99999995936)],
+              [(8400.0, 133.0), (9400.0, 113.0), None, None],
+              [(9400.0, 113.0), (10199.99999633883, 103.00000001830585), (9799.999998169415, 105.00000003661171), (10466.733333334432, 53449.66666672164)],
+              [(10200.0, 103.0), (12800.0, 90.0), None, None],
+              [(12800.0, 90.0), (12800.0, 90.0), None, None]
+    ]
+    curve = ifcopenshell.api.alignment.get_curve(alignment)
+    for segment,expected in zip(curve.Segments,expect):
+        s,e,pi,cc = ifcopenshell.api.alignment.segment_vertices(file,segment)
+        assert s == pytest.approx(expected[0])
+        assert e == pytest.approx(expected[1])
+        assert pi == pytest.approx(expected[2])
+        assert cc == pytest.approx(expected[3])
+
+test_segment_vertices()