Part: Use Tools::getNormal to compute normal to surface

src/Mod/Part/App/Attacher.cpp

@@ -62,6 +62,7 @@
 
 #include "Attacher.h"
 #include "AttachExtension.h"
+#include "Tools.h"
 #include <Base/Console.h>
 #include <App/OriginFeature.h>
 #include <App/Application.h>
@@ -1177,7 +1178,6 @@ Base::Placement AttachEngine3D::calculateAttachedPlacement(const Base::Placement
         if (vertex.IsNull())
             throw Base::ValueError("Null vertex in AttachEngine3D::calculateAttachedPlacement()!");
 
-        BRepAdaptor_Surface surf (face);
         Handle (Geom_Surface) hSurf = BRep_Tool::Surface(face);
         gp_Pnt p = BRep_Tool::Pnt(vertex);
 
@@ -1185,19 +1185,33 @@ Base::Placement AttachEngine3D::calculateAttachedPlacement(const Base::Placement
         double u, v;
         if (projector.NbPoints()==0)
             throw Base::ValueError("AttachEngine3D::calculateAttachedPlacement: projecting point onto surface failed.");
+
         projector.LowerDistanceParameters(u, v);
-
-        BRepLProp_SLProps prop(surf,u,v,1, Precision::Confusion());
-        SketchNormal = prop.Normal();
-
+        BRepAdaptor_Surface surf(face);
+        BRepLProp_SLProps prop(surf, u, v, 1, Precision::Confusion());
         gp_Dir dirX;
-        prop.TangentU(dirX); //if normal is defined, this should be defined too
+        Standard_Boolean done;
+
+        Tools::getNormal(face, u, v, Precision::Confusion(), SketchNormal, done);
+
+        if (!done)
+            throw Base::ValueError("AttachEngine3D::calculateAttachedPlacement: finding normal to surface at projected point failed.");
+
+        // if getNormal succeeds, at least one of the tangent is defined
+        if (prop.IsTangentUDefined()) {
+            prop.TangentU(dirX);
+            if (face.Orientation() == TopAbs_REVERSED)
+                dirX.Reverse();
+        }
+        // here the orientation of dirX is managed by SketchNormal orientation
+        else {
+            gp_Dir dirY;
+            prop.TangentV(dirY);
+            dirX = dirY.Crossed(SketchNormal);
+        }
+
         SketchXAxis = gp_Vec(dirX).Reversed();//yields upside-down sketches less often.
 
-        if (face.Orientation() == TopAbs_REVERSED) {
-            SketchNormal.Reverse();
-            SketchXAxis.Reverse();
-        }
         if (bThruVertex) {
             SketchBasePoint = p;
         } else {

src/Mod/Part/App/Geometry.cpp

@@ -145,6 +145,7 @@
 #include "GeometryMigrationExtension.h"
 
 #include "Geometry.h"
+#include "Tools.h"
 
 #if OCC_VERSION_HEX >= 0x070600
 using GeomAdaptor_HCurve = GeomAdaptor_Curve;
@@ -4235,11 +4236,12 @@ bool GeomSurface::tangentV(double u, double v, gp_Dir& dirV) const
 bool GeomSurface::normal(double u, double v, gp_Dir& dir) const
 {
     Handle(Geom_Surface) s = Handle(Geom_Surface)::DownCast(handle());
-    GeomLProp_SLProps prop(s,u,v,2,Precision::Confusion());
-    if (prop.IsNormalDefined()) {
-        dir = prop.Normal();
+    Standard_Boolean done;
+
+    Tools::getNormal(s, u, v, Precision::Confusion(), dir, done);
+
+    if (done)
         return true;
-    }
 
     return false;
 }

src/Mod/Part/App/TopoShapeFacePyImp.cpp

@@ -521,23 +521,20 @@ PyObject* TopoShapeFacePy::normalAt(PyObject *args)
 {
     double u,v;
     if (!PyArg_ParseTuple(args, "dd",&u,&v))
-        return 0;
+        return nullptr;
 
     const TopoDS_Face& f = TopoDS::Face(getTopoShapePtr()->getShape());
-    BRepAdaptor_Surface adapt(f);
+    Standard_Boolean done;
+    gp_Dir dir;
 
-    BRepLProp_SLProps prop(adapt,u,v,2,Precision::Confusion());
-    if (prop.IsNormalDefined()) {
-        gp_Pnt pnt; gp_Vec vec;
-        // handles the orientation state of the shape
-        BRepGProp_Face(f).Normal(u,v,pnt,vec);
-        vec.Normalize();
-        return new Base::VectorPy(new Base::Vector3d(vec.X(),vec.Y(),vec.Z()));
-    }
-    else {
+    Tools::getNormal(f, u, v, Precision::Confusion(), dir, done);
+
+    if (!done) {
         PyErr_SetString(PartExceptionOCCError, "normal not defined");
-        return 0;
+        return nullptr;
     }
+
+    return new Base::VectorPy(new Base::Vector3d(dir.X(),dir.Y(),dir.Z()));
 }
 
 PyObject* TopoShapeFacePy::getUVNodes(PyObject *args)