PyObject* GeometrySurfacePy::vIso(PyObject * args)
{
    double v;
    if (!PyArg_ParseTuple(args, "d", &v))
        return 0;

    try {
        Handle_Geom_Surface surf = Handle_Geom_Surface::DownCast
            (getGeometryPtr()->handle());
        Handle_Geom_Curve c = surf->VIso(v);
        if (c->IsKind(STANDARD_TYPE(Geom_Line))) {
            Handle_Geom_Line aLine = Handle_Geom_Line::DownCast(c);
            GeomLineSegment* line = new GeomLineSegment();
            Handle_Geom_TrimmedCurve this_curv = Handle_Geom_TrimmedCurve::DownCast
                (line->handle());
            Handle_Geom_Line this_line = Handle_Geom_Line::DownCast
                (this_curv->BasisCurve());
            this_line->SetLin(aLine->Lin());
            return new LinePy(line);
        }
        else {
            return Py::new_reference_to(makeGeometryCurvePy(c));
        }
    }
    catch (Standard_Failure) {
        Handle_Standard_Failure e = Standard_Failure::Caught();
        PyErr_SetString(PartExceptionOCCError, e->GetMessageString());
        return 0;
    }
}
const Py::Object makeGeometryCurvePy(const Handle_Geom_Curve& c)
{
    if (c->IsKind(STANDARD_TYPE(Geom_Circle))) {
        Handle_Geom_Circle circ = Handle_Geom_Circle::DownCast(c);
        return Py::asObject(new CirclePy(new GeomCircle(circ)));
    }
    else if (c->IsKind(STANDARD_TYPE(Geom_Ellipse))) {
        Handle_Geom_Ellipse ell = Handle_Geom_Ellipse::DownCast(c);
        return Py::asObject(new EllipsePy(new GeomEllipse(ell)));
    }
    else if (c->IsKind(STANDARD_TYPE(Geom_Hyperbola))) {
        Handle_Geom_Hyperbola hyp = Handle_Geom_Hyperbola::DownCast(c);
        return Py::asObject(new HyperbolaPy(new GeomHyperbola(hyp)));
    }
    else if (c->IsKind(STANDARD_TYPE(Geom_Line))) {
        Handle_Geom_Line lin = Handle_Geom_Line::DownCast(c);
        return Py::asObject(new GeometryCurvePy(new GeomLine(lin)));
    }
    else if (c->IsKind(STANDARD_TYPE(Geom_OffsetCurve))) {
        Handle_Geom_OffsetCurve oc = Handle_Geom_OffsetCurve::DownCast(c);
        return Py::asObject(new OffsetCurvePy(new GeomOffsetCurve(oc)));
    }
    else if (c->IsKind(STANDARD_TYPE(Geom_Parabola))) {
        Handle_Geom_Parabola par = Handle_Geom_Parabola::DownCast(c);
        return Py::asObject(new ParabolaPy(new GeomParabola(par)));
    }
    else if (c->IsKind(STANDARD_TYPE(Geom_TrimmedCurve))) {
        Handle_Geom_TrimmedCurve trc = Handle_Geom_TrimmedCurve::DownCast(c);
        return Py::asObject(new GeometryCurvePy(new GeomTrimmedCurve(trc)));
    }
    /*else if (c->IsKind(STANDARD_TYPE(Geom_BoundedCurve))) {
        Handle_Geom_BoundedCurve bc = Handle_Geom_BoundedCurve::DownCast(c);
        return Py::asObject(new GeometryCurvePy(new GeomBoundedCurve(bc)));
    }*/
    else if (c->IsKind(STANDARD_TYPE(Geom_BezierCurve))) {
        Handle_Geom_BezierCurve bezier = Handle_Geom_BezierCurve::DownCast(c);
        return Py::asObject(new BezierCurvePy(new GeomBezierCurve(bezier)));
    }
    else if (c->IsKind(STANDARD_TYPE(Geom_BSplineCurve))) {
        Handle_Geom_BSplineCurve bspline = Handle_Geom_BSplineCurve::DownCast(c);
        return Py::asObject(new BSplineCurvePy(new GeomBSplineCurve(bspline)));
    }

    std::string err = "Unhandled curve type ";
    err += c->DynamicType()->Name();
    throw Py::TypeError(err);
}
App::DocumentObjectExecReturn *Draft::execute(void)
{
    // Get parameters
    // Base shape
    Part::TopoShape TopShape;
    try {
        TopShape = getBaseShape();
    } catch (Base::Exception& e) {
        return new App::DocumentObjectExecReturn(e.what());
    }

    // Faces where draft should be applied
    // Note: Cannot be const reference currently because of BRepOffsetAPI_DraftAngle::Remove() bug, see below
    std::vector<std::string> SubVals = Base.getSubValuesStartsWith("Face");
    if (SubVals.size() == 0)
        return new App::DocumentObjectExecReturn("No faces specified");

    // Draft angle
    double angle = Angle.getValue() / 180.0 * M_PI;

    // Pull direction
    gp_Dir pullDirection;
    App::DocumentObject* refDirection = PullDirection.getValue();    
    if (refDirection != NULL) {
        if (refDirection->getTypeId().isDerivedFrom(PartDesign::Line::getClassTypeId())) {
                    PartDesign::Line* line = static_cast<PartDesign::Line*>(refDirection);
                    Base::Vector3d d = line->getDirection();
                    pullDirection = gp_Dir(d.x, d.y, d.z);
        } else if (refDirection->getTypeId().isDerivedFrom(Part::Feature::getClassTypeId())) {
            std::vector<std::string> subStrings = PullDirection.getSubValues();
            if (subStrings.empty() || subStrings[0].empty())
                throw Base::Exception("No pull direction reference specified");

            Part::Feature* refFeature = static_cast<Part::Feature*>(refDirection);
            Part::TopoShape refShape = refFeature->Shape.getShape();
            TopoDS_Shape ref = refShape.getSubShape(subStrings[0].c_str());

            if (ref.ShapeType() == TopAbs_EDGE) {
                TopoDS_Edge refEdge = TopoDS::Edge(ref);
                if (refEdge.IsNull())
                    throw Base::Exception("Failed to extract pull direction reference edge");
                BRepAdaptor_Curve adapt(refEdge);
                if (adapt.GetType() != GeomAbs_Line)
                    throw Base::Exception("Pull direction reference edge must be linear");

                pullDirection = adapt.Line().Direction();
            } else {
                throw Base::Exception("Pull direction reference must be an edge or a datum line");
            }
        } else {
            throw Base::Exception("Pull direction reference must be an edge of a feature or a datum line");
        }

        TopLoc_Location invObjLoc = this->getLocation().Inverted();
        pullDirection.Transform(invObjLoc.Transformation());
    }

    // Neutral plane
    gp_Pln neutralPlane;
    App::DocumentObject* refPlane = NeutralPlane.getValue();
    if (refPlane == NULL) {
        // Try to guess a neutral plane from the first selected face
        // Get edges of first selected face
        TopoDS_Shape face = TopShape.getSubShape(SubVals[0].c_str());
        TopTools_IndexedMapOfShape mapOfEdges;
        TopExp::MapShapes(face, TopAbs_EDGE, mapOfEdges);
        bool found = false;

        for (int i = 1; i <= mapOfEdges.Extent(); i++) {
            // Note: What happens if mapOfEdges(i) is the degenerated edge of a cone?
            // But in that case the draft is not possible anyway!
            BRepAdaptor_Curve c(TopoDS::Edge(mapOfEdges(i)));
            gp_Pnt p1 = c.Value(c.FirstParameter());
            gp_Pnt p2 = c.Value(c.LastParameter());

            if (c.IsClosed()) {
                // Edge is a circle or a circular arc (other types are not allowed for drafting)
                neutralPlane = gp_Pln(p1, c.Circle().Axis().Direction());
                found = true;
                break;
            } else {
                // Edge is linear
                // Find midpoint of edge and create auxiliary plane through midpoint normal to edge
                gp_Pnt pm = c.Value((c.FirstParameter() + c.LastParameter()) / 2.0);
                Handle_Geom_Plane aux = new Geom_Plane(pm, gp_Dir(p2.X() - p1.X(), p2.Y() - p1.Y(), p2.Z() - p1.Z()));
                // Intersect plane with face. Is there no easier way?
                BRepAdaptor_Surface adapt(TopoDS::Face(face), Standard_False);
                Handle_Geom_Surface sf = adapt.Surface().Surface();
                GeomAPI_IntSS intersector(aux, sf, Precision::Confusion());
                if (!intersector.IsDone())
                    continue;
                Handle_Geom_Curve icurve = intersector.Line(1);
                if (!icurve->IsKind(STANDARD_TYPE(Geom_Line)))
                    continue;
                // TODO: How to extract the line from icurve without creating an edge first?
                TopoDS_Edge edge = BRepBuilderAPI_MakeEdge(icurve);
                BRepAdaptor_Curve c(edge);
                neutralPlane = gp_Pln(pm, c.Line().Direction());
                found = true;
                break;
            }
        }

        if (!found)
            throw Base::Exception("No neutral plane specified and none can be guessed");
    } else {
        if (refPlane->getTypeId().isDerivedFrom(PartDesign::Plane::getClassTypeId())) {
            PartDesign::Plane* plane = static_cast<PartDesign::Plane*>(refPlane);
            Base::Vector3d b = plane->getBasePoint();
            Base::Vector3d n = plane->getNormal();
            neutralPlane = gp_Pln(gp_Pnt(b.x, b.y, b.z), gp_Dir(n.x, n.y, n.z));
        } else if (refPlane->getTypeId().isDerivedFrom(App::Plane::getClassTypeId())) {
            neutralPlane = Feature::makePlnFromPlane(refPlane);
        } else if (refPlane->getTypeId().isDerivedFrom(Part::Feature::getClassTypeId())) {
            std::vector<std::string> subStrings = NeutralPlane.getSubValues();
            if (subStrings.empty() || subStrings[0].empty())
                throw Base::Exception("No neutral plane reference specified");

            Part::Feature* refFeature = static_cast<Part::Feature*>(refPlane);
            Part::TopoShape refShape = refFeature->Shape.getShape();
            TopoDS_Shape ref = refShape.getSubShape(subStrings[0].c_str());

            if (ref.ShapeType() == TopAbs_FACE) {
                TopoDS_Face refFace = TopoDS::Face(ref);
                if (refFace.IsNull())
                    throw Base::Exception("Failed to extract neutral plane reference face");
                BRepAdaptor_Surface adapt(refFace);
                if (adapt.GetType() != GeomAbs_Plane)
                    throw Base::Exception("Neutral plane reference face must be planar");

                neutralPlane = adapt.Plane();
            } else if (ref.ShapeType() == TopAbs_EDGE) {
                if (refDirection != NULL) {
                    // Create neutral plane through edge normal to pull direction
                    TopoDS_Edge refEdge = TopoDS::Edge(ref);
                    if (refEdge.IsNull())
                        throw Base::Exception("Failed to extract neutral plane reference edge");
                    BRepAdaptor_Curve c(refEdge);
                    if (c.GetType() != GeomAbs_Line)
                        throw Base::Exception("Neutral plane reference edge must be linear");
                    double a = c.Line().Angle(gp_Lin(c.Value(c.FirstParameter()), pullDirection));
                    if (std::fabs(a - M_PI_2) > Precision::Confusion())
                        throw Base::Exception("Neutral plane reference edge must be normal to pull direction");
                    neutralPlane = gp_Pln(c.Value(c.FirstParameter()), pullDirection);
                } else {
                    throw Base::Exception("Neutral plane reference can only be an edge if pull direction is defined");
                }
            } else {
                throw Base::Exception("Neutral plane reference must be a face");
            }
        } else {
            throw Base::Exception("Neutral plane reference must be face of a feature or a datum plane");
        }

        TopLoc_Location invObjLoc = this->getLocation().Inverted();
        neutralPlane.Transform(invObjLoc.Transformation());
    }

    if (refDirection == NULL) {
        // Choose pull direction normal to neutral plane
        pullDirection = neutralPlane.Axis().Direction();
    }

    // Reversed pull direction
    bool reversed = Reversed.getValue();
    if (reversed)
        angle *= -1.0;

    this->positionByBaseFeature();
    // create an untransformed copy of the base shape
    Part::TopoShape baseShape(TopShape);
    baseShape.setTransform(Base::Matrix4D());
    try {
        BRepOffsetAPI_DraftAngle mkDraft;
        // Note:
        // LocOpe_SplitDrafts can split a face with a wire and apply draft to both parts
        //       Not clear though whether the face must have free boundaries
        // LocOpe_DPrism can create a stand-alone draft prism. The sketch can only have a single
        //       wire, though.
        // BRepFeat_MakeDPrism requires a support for the operation but will probably support multiple
        //       wires in the sketch

        bool success;

        do {
            success = true;
            mkDraft.Init(baseShape.getShape());

            for (std::vector<std::string>::iterator it=SubVals.begin(); it != SubVals.end(); ++it) {
                TopoDS_Face face = TopoDS::Face(baseShape.getSubShape(it->c_str()));
                // TODO: What is the flag for?
                mkDraft.Add(face, pullDirection, angle, neutralPlane);
                if (!mkDraft.AddDone()) {
                    // Note: the function ProblematicShape returns the face on which the error occurred
                    // Note: mkDraft.Remove() stumbles on a bug in Draft_Modification::Remove() and is
                    //       therefore unusable. See http://forum.freecadweb.org/viewtopic.php?f=10&t=3209&start=10#p25341
                    //       The only solution is to discard mkDraft and start over without the current face
                    // mkDraft.Remove(face);
                    Base::Console().Error("Adding face failed on %s. Omitted\n", it->c_str());
                    success = false;
                    SubVals.erase(it);
                    break;
                }
            }
        }
        while (!success);

        mkDraft.Build();
        if (!mkDraft.IsDone())
            return new App::DocumentObjectExecReturn("Failed to create draft");

        TopoDS_Shape shape = mkDraft.Shape();
        if (shape.IsNull())
            return new App::DocumentObjectExecReturn("Resulting shape is null");

        this->Shape.setValue(getSolid(shape));
        return App::DocumentObject::StdReturn;
    }
    catch (Standard_Failure) {
        Handle_Standard_Failure e = Standard_Failure::Caught();
        return new App::DocumentObjectExecReturn(e->GetMessageString());
    }
}