From b02705d79f2e1adc7773f0c845e0acc5ae8fde4b Mon Sep 17 00:00:00 2001
From: wmayer <wmayer@users.sourceforge.net>
Date: Fri, 27 May 2022 14:44:35 +0200
Subject: [PATCH] Part: apply OCC's fix for ElSLib::ConeDN and write a unit
 test

---
 src/Mod/Part/App/Geometry.cpp | 10 +++++++---
 src/Mod/Part/TestPartApp.py   | 31 ++++++++++++++++++++++++++++++-
 2 files changed, 37 insertions(+), 4 deletions(-)

diff --git a/src/Mod/Part/App/Geometry.cpp b/src/Mod/Part/App/Geometry.cpp
index ae5ca04031..9158d69e84 100644
--- a/src/Mod/Part/App/Geometry.cpp
+++ b/src/Mod/Part/App/Geometry.cpp
@@ -4591,6 +4591,10 @@ PyObject *GeomCone::getPyObject(void)
 
 gp_Vec GeomCone::getDN(double u, double v, int Nu, int Nv) const
 {
+    // Will be fixed in OCC 7.7
+#if OCC_VERSION_HEX >= 0x070700
+    return GeomSurface::getDN(u, v, Nu, Nv);
+#else
     // Copied from ElSLib::ConeDN() and applied the needed fix
     auto ElSLib__ConeDN = [](const Standard_Real U,
                              const Standard_Real V,
@@ -4602,7 +4606,6 @@ gp_Vec GeomCone::getDN(double u, double v, int Nu, int Nv) const
     {
        gp_XYZ Xdir = Pos.XDirection().XYZ();
        gp_XYZ Ydir = Pos.YDirection().XYZ();
-       gp_XYZ ZDir = Pos.Direction ().XYZ();
        Standard_Real Um = U + Nu * M_PI_2;  // M_PI * 0.5
        Xdir.Multiply(cos(Um));
        Ydir.Multiply(sin(Um));
@@ -4614,8 +4617,8 @@ gp_Vec GeomCone::getDN(double u, double v, int Nu, int Nv) const
        }
        else if(Nv == 1) {
          Xdir.Multiply(sin(SAngle));
-         ZDir.Multiply(cos(SAngle));
-         Xdir.Add(ZDir);
+         if (Nu == 0)
+           Xdir.Add(Pos.Direction().XYZ() * cos(SAngle));
          return gp_Vec(Xdir);
        }
        return gp_Vec(0.0,0.0,0.0);
@@ -4631,6 +4634,7 @@ gp_Vec GeomCone::getDN(double u, double v, int Nu, int Nv) const
     else {
       return ElSLib__ConeDN(u, v, s->Position(), s->RefRadius(), s->SemiAngle(), Nu, Nv);
     }
+#endif
 }
 
 // -------------------------------------------------
diff --git a/src/Mod/Part/TestPartApp.py b/src/Mod/Part/TestPartApp.py
index 2002d4b944..2777fffeea 100644
--- a/src/Mod/Part/TestPartApp.py
+++ b/src/Mod/Part/TestPartApp.py
@@ -20,7 +20,8 @@
 #**************************************************************************
 
 import FreeCAD, unittest, Part
-import copy 
+import copy
+import math
 from FreeCAD import Units
 from FreeCAD import Base
 App = FreeCAD
@@ -201,3 +202,31 @@ class PartTestCircle2D(unittest.TestCase):
         p3 = App.Base.Vector2d(0.04, 0.0399)
         with self.assertRaises(ValueError):
             Part.Geom2d.Circle2d.getCircleCenter(p1, p2, p3)
+
+class PartTestCone(unittest.TestCase):
+    def testderivatives(self):
+        def get_dn(surface, u, v):
+            pos = surface.value(u, v)
+            v10 = surface.getDN(u, v, 1, 0)
+            v01 = surface.getDN(u, v, 0, 1)
+            v11 = surface.getDN(u, v, 1, 1)
+            return (pos, v10, v01, v11)
+
+        cone = Part.Cone()
+        cone.SemiAngle = 0.2
+        cone.Radius = 2.0
+
+        u, v = (5.0, 5.0)
+        vp, v1, v2, v3 = get_dn(cone, u, v)
+
+        shape = cone.toShape(0, 2*math.pi, 0, 10)
+        shape = shape.toNurbs()
+        spline = shape.Face1.Surface
+
+        u, v = spline.parameter(vp)
+        wp, w1, w2, w3 = get_dn(spline, u, v)
+
+        self.assertAlmostEqual(vp.distanceToPoint(wp), 0)
+        self.assertAlmostEqual(v1.getAngle(w1), 0)
+        self.assertAlmostEqual(v2.getAngle(w2), 0)
+        self.assertAlmostEqual(v3.getAngle(w3), 0)