From 41a88bcd4dbd40c5a150427a71e193bca485a283 Mon Sep 17 00:00:00 2001
From: civilx64 <26513472+civilx64@users.noreply.github.com>
Date: Thu, 27 Aug 2020 23:31:51 -0400
Subject: [PATCH] create implementation of IfcTransitionCurveSegment2D

---
 .../ifcopenshell/transition_curve.py          | 127 ++++++++++++++++++
 1 file changed, 127 insertions(+)
 create mode 100644 src/ifcopenshell-python/ifcopenshell/transition_curve.py

diff --git a/src/ifcopenshell-python/ifcopenshell/transition_curve.py b/src/ifcopenshell-python/ifcopenshell/transition_curve.py
new file mode 100644
index 0000000000..d97a621afb
--- /dev/null
+++ b/src/ifcopenshell-python/ifcopenshell/transition_curve.py
@@ -0,0 +1,127 @@
+###############################################################################
+#                                                                             #
+# This file is part of IfcOpenShell.                                          #
+#                                                                             #
+# IfcOpenShell is free software: you can redistribute it and/or modify        #
+# it under the terms of the Lesser GNU General Public License as published by #
+# the Free Software Foundation, either version 3.0 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                #
+# Lesser GNU General Public License for more details.                         #
+#                                                                             #
+# You should have received a copy of the Lesser GNU General Public License    #
+# along with this program. If not, see <http://www.gnu.org/licenses/>.        #
+#                                                                             #
+###############################################################################
+
+from enum import Enum
+from dataclasses import DataClass
+import math
+
+from OCC.gp import gp_Pnt2d
+from OCC.BRepBuilderAPI import BRepBuilderAPI_MakeEdge
+from OCC.BRepBuilderAPI import BRepBuilderAPI_MakeWire
+
+
+class IfcTransitionCurveType(Enum):
+    """IFC 4.1 Section 8.9.2.9
+    [https://standards.buildingsmart.org/IFC/RELEASE/IFC4_1/FINAL/HTML/schema/ifcgeometryresource/lexical/ifctransitioncurvetype.htm]
+
+    The IfcTransitionCurveType indicates the curvature of a transition curve.
+    """
+    BIQUADRATICPARABOLA = 1  # NOTE also referred to as Schramm curve.
+    BLOSSCURVE = 2
+    CLOTHOIDCURVE = 3
+    COSINECURVE = 4
+    CUBICPARABOLA = 5
+    SINECURVE = 6  # NOTE also referred to as Klein curve
+
+
+@DataClass
+class IfcTransitionSegment2D:
+    """IFC 4.1 Section 8.9.3.65
+    [https://standards.buildingsmart.org/IFC/RELEASE/IFC4_1/FINAL/HTML/schema/ifcgeometryresource/lexical/ifctransitioncurvesegment2d.htm]
+
+    A curve that transitions between a straight line and a circular arc (or the reverse).
+    """
+    StartPoint: tuple  # IfcSchema::IfcCartesianPoint
+    StartDirection: float  # IfcSchema::IfcPlaneAngleMeasure
+    SegmentLength: float  # IfcSchema::IfcPositiveLengthMeasure
+    StartRadius: float = None  # IfcSchema::IfcPositiveLengthMeasure
+    EndRadius: float = None  # IfcSchema::IfcPositiveLengthMeasure
+    IsStartRadiusCCW: bool  # IfcSchema::IfcBoolean
+    IsEndRadiusCCW: bool  # IfcSchema::IfcBoolean
+    TransitionCurveType: IfcTransitionCurveType
+
+
+def _calc_biquadratic_parabola_point(lpt, L, R, ccw):
+    pass
+
+
+def _calc_bloss_curve_point(lpt, L, R, ccw):
+    pass
+
+
+def _calc_clothoid_curve_point(lpt, L, R, ccw):
+    pass
+
+
+def _calc_cosine_curve_point(lpt, L, R, ccw):
+    pass
+
+
+def _calc_cubic_parabola_point(lpt, L, R, ccw):
+
+    x = lpt
+    y = (x ** 3) / (6 * R * L)
+    if not ccw:
+        y = -1 * y
+
+    return gp_Pnt2d(x, y)
+
+
+def _calc_sine_curve_point(lpt, L, R, ccw):
+    pass
+
+
+def _calc_transition_curve_point(lpt, L, R, ccw, trans_type):
+
+    if trans_type == "CUBICPARABOLA":
+        x, y = _calc_cubic_parabola_point(lpt, L, R, ccw)
+        return gp_Pnt2d(x, y)
+    else:
+        raise ValueError(f"Transition Curve type '{trans_type}' not implemented yet.")
+
+
+def convert_IfcTransitionSegment2D(segment, stroking_interval=5.0):
+    """convert IfcTransitionSegment2D to OCC wire
+
+    :param segment: ifc entity to be parsed into geometry
+    :type segment: IfcTransitionSegment2D
+    :param stroking_interval: maximum curve length between points to be calculated
+    :type stroking_interval: float
+    :return: OCC wire containing interpolated points
+    """
+    points = list()
+
+    L = segment.SegmentLength
+    R = segment.EndRadius
+    ccw = segment.IsstartRadiusCCW
+    trans_type = segment.TransitionCurveType.name
+
+    num_intervals = math.ceil(L / stroking_interval)
+    interval_dist = L / num_intervals
+    lpt = 0.0  # length along the curve at the point to be calculated
+
+    for _ in num_intervals:
+        points.append(_calc_transition_curve_point(
+            lpt, L, R, ccw, trans_type
+            ))
+        lpt += interval_dist
+
+    e = BRepBuilderAPI_MakeEdge(points)
+
+    return BRepBuilderAPI_MakeWire(e)