src/Mod/PartDesign/App/FeatureHelix.cpp

/***************************************************************************
 *   Copyright (c) 2010 Juergen Riegel <FreeCAD@juergen-riegel.net>        *
 *                 2020 David Österberg                                    *
 *   This file is part of the FreeCAD CAx development system.              *
 *                                                                         *
 *   This library is free software; you can redistribute it and/or         *
 *   modify it under the terms of the GNU Library General Public           *
 *   License as published by the Free Software Foundation; either          *
 *   version 2 of the License, or (at your option) any later version.      *
 *                                                                         *
 *   This library  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 Library General Public License for more details.                  *
 *                                                                         *
 *   You should have received a copy of the GNU Library General Public     *
 *   License along with this library; see the file COPYING.LIB. If not,    *
 *   write to the Free Software Foundation, Inc., 59 Temple Place,         *
 *   Suite 330, Boston, MA  02111-1307, USA                                *
 *                                                                         *
 ***************************************************************************/

#include <limits>
#include <BRepAdaptor_Surface.hxx>
#include <Mod/Part/App/FCBRepAlgoAPI_Common.h>
#include <Mod/Part/App/FCBRepAlgoAPI_Cut.h>
#include <Mod/Part/App/FCBRepAlgoAPI_Fuse.h>
#include <BRepBndLib.hxx>
#include <BRepBuilderAPI_MakeSolid.hxx>
#include <BRepBuilderAPI_Sewing.hxx>
#include <BRepClass3d_SolidClassifier.hxx>
#include <BRepOffsetAPI_MakePipe.hxx>
#include <BRepOffsetAPI_MakePipeShell.hxx>
#include <BRepPrimAPI_MakeRevol.hxx>
#include <ShapeFix_ShapeTolerance.hxx>
#include <ShapeFix_Solid.hxx>
#include <Precision.hxx>
#include <TopoDS.hxx>
#include <TopoDS_Face.hxx>
#include <TopoDS_Wire.hxx>
#include <gp_Ax1.hxx>
#include <gp_Ax3.hxx>

#include <Standard_Version.hxx>
#include <Base/Axis.h>
#include <Base/Exception.h>
#include <Base/Placement.h>
#include <Base/Tools.h>

#include <Mod/Part/App/TopoShape.h>
#include <Mod/Part/App/FaceMakerCheese.h>

#include "FeatureHelix.h"

using namespace PartDesign;

const char* Helix::ModeEnums[]
    = {"pitch-height-angle", "pitch-turns-angle", "height-turns-angle", "height-turns-growth", nullptr};

PROPERTY_SOURCE(PartDesign::Helix, PartDesign::ProfileBased)

// we purposely use not FLT_MAX because this would not be computable
const App::PropertyFloatConstraint::Constraints Helix::floatTurns
    = {Precision::Confusion(), std::numeric_limits<int>::max(), 1.0};
const App::PropertyFloatConstraint::Constraints Helix::floatTolerance
    = {0.1, std::numeric_limits<int>::max(), 1.0};
const App::PropertyAngle::Constraints Helix::floatAngle = {-89.0, 89.0, 1.0};

Helix::Helix()
{
    addSubType = FeatureAddSub::Additive;
    auto initialMode = HelixMode::pitch_height_angle;

    const char* group = "Helix";
    ADD_PROPERTY_TYPE(
        Base,
        (Base::Vector3d(0.0, 0.0, 0.0)),
        group,
        App::Prop_ReadOnly,
        QT_TRANSLATE_NOOP(
            "App::Property",
            "The center point of the helix' start; derived from the reference axis."
        )
    );
    ADD_PROPERTY_TYPE(
        Axis,
        (Base::Vector3d(0.0, 1.0, 0.0)),
        group,
        App::Prop_ReadOnly,
        QT_TRANSLATE_NOOP("App::Property", "The helix' direction; derived from the reference axis.")
    );
    ADD_PROPERTY_TYPE(
        ReferenceAxis,
        (nullptr),
        group,
        App::Prop_None,
        QT_TRANSLATE_NOOP("App::Property", "The reference axis of the helix.")
    );
    ADD_PROPERTY_TYPE(
        Mode,
        (long(initialMode)),
        group,
        App::Prop_None,
        QT_TRANSLATE_NOOP(
            "App::Property",
            "The helix input mode specifies which properties are set by the user.\n"
            "Dependent properties are then calculated."
        )
    );
    Mode.setEnums(ModeEnums);
    ADD_PROPERTY_TYPE(
        Pitch,
        (10.0),
        group,
        App::Prop_None,
        QT_TRANSLATE_NOOP("App::Property", "The axial distance between two turns.")
    );
    ADD_PROPERTY_TYPE(
        Height,
        (30.0),
        group,
        App::Prop_None,
        QT_TRANSLATE_NOOP(
            "App::Property",
            "The height of the helix' path, not accounting for the extent of the profile."
        )
    );
    ADD_PROPERTY_TYPE(
        Turns,
        (3.0),
        group,
        App::Prop_None,
        QT_TRANSLATE_NOOP("App::Property", "The number of turns in the helix.")
    );
    Turns.setConstraints(&floatTurns);
    ADD_PROPERTY_TYPE(
        Angle,
        (0.0),
        group,
        App::Prop_None,
        QT_TRANSLATE_NOOP(
            "App::Property",
            "The angle of the cone that forms a hull around the helix.\n"
            "Non-zero values turn the helix into a conical spiral.\n"
            "Positive values make the radius grow, negative shrinks."
        )
    );
    Angle.setConstraints(&floatAngle);
    ADD_PROPERTY_TYPE(
        Growth,
        (0.0),
        group,
        App::Prop_None,
        QT_TRANSLATE_NOOP(
            "App::Property",
            "The growth of the helix' radius per turn.\n"
            "Non-zero values turn the helix into a conical spiral."
        )
    );
    ADD_PROPERTY_TYPE(
        LeftHanded,
        (false),
        group,
        App::Prop_None,
        QT_TRANSLATE_NOOP(
            "App::Property",
            "Sets the turning direction to left handed,\n"
            "i.e. counter-clockwise when moving along its axis."
        )
    );
    ADD_PROPERTY_TYPE(
        Reversed,
        (false),
        group,
        App::Prop_None,
        QT_TRANSLATE_NOOP(
            "App::Property",
            "Determines whether the helix points in the opposite direction of the axis."
        )
    );
    ADD_PROPERTY_TYPE(
        Outside,
        (false),
        group,
        App::Prop_None,
        QT_TRANSLATE_NOOP(
            "App::Property",
            "If set, the result will be the intersection of the profile and the preexisting body."
        )
    );
    ADD_PROPERTY_TYPE(
        HasBeenEdited,
        (false),
        group,
        App::Prop_Hidden,
        QT_TRANSLATE_NOOP(
            "App::Property",
            "If false, the tool will propose an initial value for the pitch based on the profile "
            "bounding box,\n"
            "so that self intersection is avoided."
        )
    );
    ADD_PROPERTY_TYPE(
        Tolerance,
        (0.1),
        group,
        App::Prop_None,
        QT_TRANSLATE_NOOP("App::Property", "Fusion Tolerance for the Helix, increase if helical shape does not merge nicely with part.")
    );
    Tolerance.setConstraints(&floatTolerance);

    setReadWriteStatusForMode(initialMode);
}

short Helix::mustExecute() const
{
    if (Placement.isTouched() || ReferenceAxis.isTouched() || Axis.isTouched() || Base.isTouched()
        || Angle.isTouched()) {
        return 1;
    }
    return ProfileBased::mustExecute();
}

App::DocumentObjectExecReturn* Helix::execute()
{
    if (onlyHaveRefined()) {
        return App::DocumentObject::StdReturn;
    }

    // Validate and normalize parameters
    HelixMode mode = static_cast<HelixMode>(Mode.getValue());
    if (mode == HelixMode::pitch_height_angle) {
        if (Pitch.getValue() < Precision::Confusion()) {
            return new App::DocumentObjectExecReturn(
                QT_TRANSLATE_NOOP("Exception", "Error: Pitch too small!")
            );
        }
        if (Height.getValue() < Precision::Confusion()) {
            return new App::DocumentObjectExecReturn(
                QT_TRANSLATE_NOOP("Exception", "Error: height too small!")
            );
        }
        Turns.setValue(Height.getValue() / Pitch.getValue());
        Growth.setValue(Pitch.getValue() * tan(Base::toRadians(Angle.getValue())));
    }
    else if (mode == HelixMode::pitch_turns_angle) {
        if (Pitch.getValue() < Precision::Confusion()) {
            return new App::DocumentObjectExecReturn(
                QT_TRANSLATE_NOOP("Exception", "Error: pitch too small!")
            );
        }
        if (Turns.getValue() < Precision::Confusion()) {
            return new App::DocumentObjectExecReturn(
                QT_TRANSLATE_NOOP("Exception", "Error: turns too small!")
            );
        }
        Height.setValue(Turns.getValue() * Pitch.getValue());
        Growth.setValue(Pitch.getValue() * tan(Base::toRadians(Angle.getValue())));
    }
    else if (mode == HelixMode::height_turns_angle) {
        if (Height.getValue() < Precision::Confusion()) {
            return new App::DocumentObjectExecReturn(
                QT_TRANSLATE_NOOP("Exception", "Error: height too small!")
            );
        }
        if (Turns.getValue() < Precision::Confusion()) {
            return new App::DocumentObjectExecReturn(
                QT_TRANSLATE_NOOP("Exception", "Error: turns too small!")
            );
        }
        Pitch.setValue(Height.getValue() / Turns.getValue());
        Growth.setValue(Pitch.getValue() * tan(Base::toRadians(Angle.getValue())));
    }
    else if (mode == HelixMode::height_turns_growth) {
        if (Turns.getValue() < Precision::Confusion()) {
            return new App::DocumentObjectExecReturn(
                QT_TRANSLATE_NOOP("Exception", "Error: turns too small!")
            );
        }
        if ((Height.getValue() < Precision::Confusion())
            && (abs(Growth.getValue()) < Precision::Confusion()) && Turns.getValue() > 1.0) {
            return new App::DocumentObjectExecReturn(
                QT_TRANSLATE_NOOP("Exception", "Error: either height or growth must not be zero!")
            );
        }
        Pitch.setValue(Height.getValue() / Turns.getValue());
        if (Height.getValue() > 0) {
            Angle.setValue(
                Base::toDegrees(atan(Turns.getValue() * Growth.getValue() / Height.getValue()))
            );
        }
        else {
            // On purpose, we're doing nothing here; the else-branch is just for this comment.
            // - we don't print a warning, as for a flat spiral a zero-height is perfectly fine
            // - we don't void the angle (somehow) so that it keeps its value. This allows in
            //   interactive usage to just go back to another mode and everything keeps working
        }
    }
    else {
        return new App::DocumentObjectExecReturn(
            QT_TRANSLATE_NOOP("Exception", "Error: unsupported mode")
        );
    }

    TopoDS_Shape sketchshape;  // Fixme: Should this be TopoShape here and below?
    try {
        sketchshape = getVerifiedFace();
    }
    catch (const Base::Exception& e) {
        return new App::DocumentObjectExecReturn(e.what());
    }

    if (sketchshape.IsNull()) {
        return new App::DocumentObjectExecReturn(
            QT_TRANSLATE_NOOP("Exception", "Error: No valid sketch or face")
        );
    }
    else {
        // TODO: currently we only allow planar faces. the reason for this is that with other faces
        // in front, we could not use the current simulate approach and build the start and end face
        // from the wires. As the shell begins always at the spine and not the profile, the
        // sketchshape cannot be used directly as front face. We would need a method to translate
        // the front shape to match the shell starting position somehow...
        TopoDS_Face face = TopoDS::Face(sketchshape);
        BRepAdaptor_Surface adapt(face);
        if (adapt.GetType() != GeomAbs_Plane) {
            return new App::DocumentObjectExecReturn(
                QT_TRANSLATE_NOOP("Exception", "Error: Face must be planar")
            );
        }
    }

    // if the Base property has a valid shape, fuse the AddShape into it
    TopoShape base;
    try {
        base = getBaseTopoShape();
    }
    catch (const Base::Exception&) {
        // fall back to support (for legacy features)
        base = TopoShape();
    }

    // update Axis from ReferenceAxis
    try {
        updateAxis();
    }
    catch (const Base::Exception& e) {
        return new App::DocumentObjectExecReturn(e.what());
    }

    try {
        this->positionByPrevious();
        TopLoc_Location invObjLoc = this->getLocation().Inverted();

        base.move(invObjLoc);

        TopoDS_Shape result;

        // generate the helix path
        TopoDS_Shape path;
        if (Angle.getValue() == 0.) {
            // breaking the path at each turn prevents an OCC issue
            path = generateHelixPath();
        }
        else {
            // don't break the path or the generated solid is invalid
            path = generateHelixPath(1000.);
        }

        TopoDS_Shape face = sketchshape;
        face.Move(invObjLoc);

        Bnd_Box bounds;
        BRepBndLib::Add(path, bounds);
        double size = sqrt(bounds.SquareExtent());
        ShapeFix_ShapeTolerance fix;
        fix.LimitTolerance(path, Precision::Confusion() * 1e-6 * size);  // needed to produce valid
                                                                         // Pipe for very big parts
        // We introduce final part tolerance with the second call to LimitTolerance below, however
        // OCCT has a bug where the side-walls of the Pipe disappear with very large (km range)
        // pieces increasing a tiny bit of extra tolerance to the path fixes this. This will in any
        // case be less than the tolerance lower limit below, but sufficient to avoid the bug

        BRepOffsetAPI_MakePipe
            mkPS(TopoDS::Wire(path), face, GeomFill_Trihedron::GeomFill_IsFrenet, Standard_False);
        result = mkPS.Shape();

        BRepClass3d_SolidClassifier SC(result);
        SC.PerformInfinitePoint(Precision::Confusion());
        if (SC.State() == TopAbs_IN) {
            result.Reverse();
        }

        fix.LimitTolerance(
            result,
            Precision::Confusion() * size * Tolerance.getValue()
        );  // significant precision reduction due to helical approximation - needed to allow fusion
            // to succeed

        // try to auto-fix possible invalid result
        ShapeFix_Solid fixer;
        fixer.Init(TopoDS::Solid(result));
        if (fixer.Perform()) {
            result = fixer.Solid();
        }

        AddSubShape.setValue(result);

        if (base.isNull()) {

            if (getAddSubType() == FeatureAddSub::Subtractive) {
                return new App::DocumentObjectExecReturn(
                    QT_TRANSLATE_NOOP("Exception", "Error: There is nothing to subtract")
                );
            }

            if (!isSingleSolidRuleSatisfied(result)) {
                return new App::DocumentObjectExecReturn(
                    QT_TRANSLATE_NOOP("Exception", "Error: Result has multiple solids")
                );
            }

            // store shape before refinement
            this->rawShape = result;
            Shape.setValue(getSolid(result));
            return App::DocumentObject::StdReturn;
        }

        if (getAddSubType() == FeatureAddSub::Additive) {

            FCBRepAlgoAPI_Fuse mkFuse(base.getShape(), result);
            if (!mkFuse.IsDone()) {
                return new App::DocumentObjectExecReturn(
                    QT_TRANSLATE_NOOP("Exception", "Error: Adding the helix failed")
                );
            }
            // we have to get the solids (fuse sometimes creates compounds)
            TopoShape boolOp = this->getSolid(mkFuse.Shape());

            // lets check if the result is a solid
            if (boolOp.isNull()) {
                return new App::DocumentObjectExecReturn(
                    QT_TRANSLATE_NOOP("Exception", "Error: Result is not a solid")
                );
            }

            if (!isSingleSolidRuleSatisfied(boolOp.getShape())) {
                return new App::DocumentObjectExecReturn(
                    QT_TRANSLATE_NOOP("Exception", "Error: Result has multiple solids")
                );
            }

            // store shape before refinement
            this->rawShape = boolOp;
            boolOp = refineShapeIfActive(boolOp, RefineErrorPolicy::Warn);
            Shape.setValue(getSolid(boolOp));
        }
        else if (getAddSubType() == FeatureAddSub::Subtractive) {

            TopoShape boolOp;

            if (Outside.getValue()) {  // are we subtracting the inside or the outside of the profile.
                FCBRepAlgoAPI_Common mkCom(result, base.getShape());
                if (!mkCom.IsDone()) {
                    return new App::DocumentObjectExecReturn(
                        QT_TRANSLATE_NOOP("Exception", "Error: Intersecting the helix failed")
                    );
                }
                boolOp = this->getSolid(mkCom.Shape());
            }
            else {
                FCBRepAlgoAPI_Cut mkCut(base.getShape(), result);
                if (!mkCut.IsDone()) {
                    return new App::DocumentObjectExecReturn(
                        QT_TRANSLATE_NOOP("Exception", "Error: Subtracting the helix failed")
                    );
                }
                boolOp = this->getSolid(mkCut.Shape());
            }

            // lets check if the result is a solid
            if (boolOp.isNull()) {
                return new App::DocumentObjectExecReturn(
                    QT_TRANSLATE_NOOP("Exception", "Error: Result is not a solid")
                );
            }

            if (!isSingleSolidRuleSatisfied(boolOp.getShape())) {
                return new App::DocumentObjectExecReturn(
                    QT_TRANSLATE_NOOP("Exception", "Error: Result has multiple solids")
                );
            }

            // store shape before refinement
            this->rawShape = boolOp;
            boolOp = refineShapeIfActive(boolOp, RefineErrorPolicy::Warn);
            Shape.setValue(getSolid(boolOp));
        }

        return App::DocumentObject::StdReturn;
    }
    catch (Standard_Failure& e) {

        if (std::string(e.GetMessageString()) == "TopoDS::Face") {
            return new App::DocumentObjectExecReturn(
                QT_TRANSLATE_NOOP("Exception", "Error: Could not create face from sketch")
            );
        }
        else {
            return new App::DocumentObjectExecReturn(e.GetMessageString());
        }
    }
    catch (Base::Exception& e) {
        return new App::DocumentObjectExecReturn(e.what());
    }
}

void Helix::updateAxis()
{
    App::DocumentObject* pcReferenceAxis = ReferenceAxis.getValue();
    const std::vector<std::string>& subReferenceAxis = ReferenceAxis.getSubValues();
    Base::Vector3d base;
    Base::Vector3d dir;
    getAxis(pcReferenceAxis, subReferenceAxis, base, dir, ForbiddenAxis::NoCheck);

    Base.setValue(base.x, base.y, base.z);
    Axis.setValue(dir.x, dir.y, dir.z);
}

TopoDS_Shape Helix::generateHelixPath(double breakAtTurn)
{
    double turns = Turns.getValue();
    double height = Height.getValue();
    bool leftHanded = LeftHanded.getValue();
    bool reversed = Reversed.getValue();
    double angle = Angle.getValue();
    double growth = Growth.getValue();

    if (fabs(angle) < Precision::Confusion()) {
        angle = 0.0;
    }

    // get revolve axis
    Base::Vector3d baseVector = Base.getValue();
    gp_Pnt pnt(baseVector.x, baseVector.y, baseVector.z);
    Base::Vector3d axisVector = Axis.getValue();
    gp_Dir dir(axisVector.x, axisVector.y, axisVector.z);

    Base::Vector3d normal = getProfileNormal();
    Base::Vector3d start = axisVector.Cross(normal);  // pointing towards the desired helix start point.

    // if our axis is (nearly) aligned with the profile's normal, we're only interested in the
    // "twist" of the helix. The actual starting point, and thus the radius, isn't important as long
    // as it's somewhere in the profile's plane: an arbitrary vector perpendicular to the normal.
    if (start.IsNull()) {
        auto hopefullyNotParallel = Base::Vector3d(1.0, 2.0, 3.0);
        start = normal.Cross(hopefullyNotParallel);
        if (start.IsNull()) {
            // bad luck
            hopefullyNotParallel = Base::Vector3d(3.0, 2.0, 1.0);
            start = normal.Cross(hopefullyNotParallel);
        }
    }

    gp_Dir dir_start(start.x, start.y, start.z);

    // Find out in what quadrant relative to the axis the profile is located, and the exact position.
    Base::Vector3d profileCenter = getProfileCenterPoint();

    // The factor of 100 below ensures that profile size is small compared to the curvature of the
    // helix. This improves the issue reported in
    // https://forum.freecad.org/viewtopic.php?f=10&t=65048
    double axisOffset = 100.0 * (profileCenter * start - baseVector * start);
    double radius = std::fabs(axisOffset);
    bool turned = axisOffset < 0;
    // since the factor does not only change the radius but also the path position, we must shift
    // its offset back using the square of the factor
    double startOffset = 10000.0
        * std::fabs((angle <= 0. ? 1. : 0.) * (profileCenter * axisVector) - baseVector * axisVector);

    if (radius < Precision::Confusion()) {
        // in this case ensure that axis is not in the sketch plane
        if (fabs(axisVector * normal) < Precision::Confusion()) {
            throw Base::ValueError("Error: Result is self intersecting");
        }
        radius = 1000.0;  // fallback to radius 1000
    }

    bool growthMode = std::string(Mode.getValueAsString()).find("growth") != std::string::npos;
    double radiusTop;
    if (growthMode) {
        radiusTop = radius + turns * growth;
    }
    else {
        radiusTop = radius + height * tan(Base::toRadians(angle));
    }

    // build the helix path
    TopoDS_Shape path
        = TopoShape().makeSpiralHelix(radius, radiusTop, height, turns, breakAtTurn, leftHanded);

    /*
     * The helix wire is created with the axis coinciding with z-axis and the start point at
     * (radius, 0, 0) We want to move it so that the axis becomes aligned with "dir" and "pnt", we
     * also want (radius,0,0) to map to the sketch plane.
     */

    gp_Pnt origo(0.0, 0.0, 0.0);
    gp_Dir dir_axis1(0.0, 0.0, 1.0);  // pointing along the helix axis, as created.
    gp_Dir dir_axis2(1.0, 0.0, 0.0);  // pointing towards the helix start point, as created.
    gp_Trsf mov;

    if (abs(startOffset) > 0) {  // translate the helix so that the starting point aligns with the
                                 // profile
        mov.SetTranslation(startOffset * gp_Vec(dir_axis1));
        TopLoc_Location loc(mov);
        path.Move(loc);
    }

    // because of the radius factor we used above, we must reverse after the
    // startOffset movement (that brings the path back to the desired position)
    if (reversed) {
        mov.SetRotation(gp_Ax1(origo, dir_axis2), std::numbers::pi);
        TopLoc_Location loc(mov);
        path.Move(loc);
    }

    if (turned) {  // turn the helix so that the starting point aligns with the profile
        mov.SetRotation(gp_Ax1(origo, dir_axis1), std::numbers::pi);
        TopLoc_Location loc(mov);
        path.Move(loc);
    }

    gp_Ax3 sourceCS(origo, dir_axis1, dir_axis2);
    gp_Ax3 targetCS(pnt, dir, dir_start);

    mov.SetTransformation(sourceCS, targetCS);
    TopLoc_Location loc(mov);
    path.Move(loc.Inverted());

    TopLoc_Location invObjLoc = this->getLocation().Inverted();
    path.Move(invObjLoc);

    return path;
}

// this function calculates self intersection safe pitch based on the profile bounding box.
double Helix::safePitch()
{
    Base::Vector3d axisVec = Axis.getValue();
    Base::Vector3d startVec = axisVec.Cross(getProfileNormal());  // pointing towards the helix
                                                                  // start point
    HelixMode mode = static_cast<HelixMode>(Mode.getValue());
    double growthValue = Growth.getValue();
    double turnsValue = Turns.getValue();

    // handle case if axis is orthogonal to profile
    // since startVec.IsNull() fails sometimes, for e.g. (0.0, 0.0, -0.0)
    // we take the precision into account
    if (startVec.Length() < Precision::Confusion()) {
        // when not in growth mode any pitch > 0 is safe
        if (mode != HelixMode::height_turns_growth) {
            return Precision::Confusion();
        }
        // if growth is not zero, there will in many cases be intersections
        // when the turn is >= 1, thus return an 'infinite' pitch
        // Note: The resulting helix body is in this case often garbage since
        // the OCC algorithm to create the helix fails.
        // Nevertheless, the result is a valid body so it should be valuable for users
        // to get this correct warning anyway.
        else {
            if (abs(turnsValue) >= 1.0 && abs(growthValue) > 0.0) {
                return Precision::Infinite();
            }
        }
    }

    double angle = Base::toRadians(Angle.getValue());
    gp_Dir direction(axisVec.x, axisVec.y, axisVec.z);
    gp_Dir directionStart(startVec.x, startVec.y, startVec.z);
    TopoDS_Shape sketchshape = getVerifiedFace();
    Bnd_Box boundingBox;
    BRepBndLib::Add(sketchshape, boundingBox);

    // get boundary and dimensions of boundingBox
    double Xmin, Ymin, Zmin, Xmax, Ymax, Zmax;
    boundingBox.Get(Xmin, Ymin, Zmin, Xmax, Ymax, Zmax);
    double X = Xmax - Xmin, Y = Ymax - Ymin, Z = Zmax - Zmin;
    gp_Vec boundingBoxVec(X, Y, Z);

    // Below is an approximation because since we take the bounding box it is
    // impossible to calculate it precisely. For example a circle has as bounding
    // box a square and thus results in a larger pitch than really necessary

    // minimal safe pitch if the angle or growth is 0
    double pitch0 = boundingBoxVec * direction;

    if (mode == HelixMode::height_turns_growth) {
        // if the distance perpendicular to axisVec
        // between two turns is larger than the bounding box size in this direction
        // the minimal necessary pitch is zero
        if (abs(growthValue) > abs(boundingBoxVec * directionStart)) {
            return 0.0;
        }
        else {
            // if less than one turn, every pitch is safe
            // Note: at the moment helices with a growth end with a plane
            // whose normal is the final direction of the helix path.
            // In case this might be changed in future, also 1.0 turn would be safe.
            if (turnsValue < 1.0) {
                return 0.0;
            }
            else {
                return pitch0;
            }
        }
    }
    else {
        // if the angle is so large that the distance perpendicular to axisVec
        // between two turns is larger than the bounding box size in this direction
        // the pitch can be smaller than pitch0
        if (tan(abs(angle)) * pitch0 > abs(boundingBoxVec * directionStart)) {
            return abs(boundingBoxVec * directionStart) / tan(abs(angle));
        }
        else {
            return pitch0;
        }
    }
}

// this function proposes pitch and height
void Helix::proposeParameters(bool force)
{
    if (force || !HasBeenEdited.getValue()) {
        TopoDS_Shape sketchshape = getVerifiedFace();
        Bnd_Box bb;
        BRepBndLib::Add(sketchshape, bb);
        bb.SetGap(0.0);
        double pitch = 1.1 * sqrt(bb.SquareExtent());

        Pitch.setValue(pitch);
        Height.setValue(pitch * 3.0);
        HasBeenEdited.setValue(true);
    }
}

Base::Vector3d Helix::getProfileCenterPoint()
{
    TopoDS_Shape profileshape;
    profileshape = getVerifiedFace();
    Bnd_Box box;
    BRepBndLib::Add(profileshape, box);
    box.SetGap(0.0);
    double xmin, ymin, zmin, xmax, ymax, zmax;
    box.Get(xmin, ymin, zmin, xmax, ymax, zmax);
    return Base::Vector3d(0.5 * (xmin + xmax), 0.5 * (ymin + ymax), 0.5 * (zmin + zmax));
}

void Helix::handleChangedPropertyType(Base::XMLReader& reader, const char* TypeName, App::Property* prop)
{
    // property Turns had the App::PropertyFloat and was changed to App::PropertyFloatConstraint
    if (prop == &Turns && strcmp(TypeName, "App::PropertyFloat") == 0) {
        App::PropertyFloat TurnsProperty;
        // restore the PropertyFloat to be able to set its value
        TurnsProperty.Restore(reader);
        Turns.setValue(TurnsProperty.getValue());
    }
    // property Growth had the App::PropertyLength and was changed to App::PropertyDistance
    else if (prop == &Growth && strcmp(TypeName, "App::PropertyLength") == 0) {
        App::PropertyLength GrowthProperty;
        // restore the PropertyLength to be able to set its value
        GrowthProperty.Restore(reader);
        Growth.setValue(GrowthProperty.getValue());
    }
    else {
        ProfileBased::handleChangedPropertyType(reader, TypeName, prop);
    }
}

void Helix::onChanged(const App::Property* prop)
{
    if (prop == &Mode) {
        // Depending on the mode, the derived properties are set read-only
        auto inputMode = static_cast<HelixMode>(Mode.getValue());
        setReadWriteStatusForMode(inputMode);
    }

    ProfileBased::onChanged(prop);
}

void Helix::setReadWriteStatusForMode(HelixMode inputMode)
{
    switch (inputMode) {
        case HelixMode::pitch_height_angle:
            // primary input:
            Pitch.setStatus(App::Property::ReadOnly, false);
            Height.setStatus(App::Property::ReadOnly, false);
            Angle.setStatus(App::Property::ReadOnly, false);
            // derived props:
            Turns.setStatus(App::Property::ReadOnly, true);
            Growth.setStatus(App::Property::ReadOnly, true);
            break;

        case HelixMode::pitch_turns_angle:
            // primary input:
            Pitch.setStatus(App::Property::ReadOnly, false);
            Turns.setStatus(App::Property::ReadOnly, false);
            Angle.setStatus(App::Property::ReadOnly, false);
            // derived props:
            Height.setStatus(App::Property::ReadOnly, true);
            Growth.setStatus(App::Property::ReadOnly, true);
            break;

        case HelixMode::height_turns_angle:
            // primary input:
            Height.setStatus(App::Property::ReadOnly, false);
            Turns.setStatus(App::Property::ReadOnly, false);
            Angle.setStatus(App::Property::ReadOnly, false);
            // derived props:
            Pitch.setStatus(App::Property::ReadOnly, true);
            Growth.setStatus(App::Property::ReadOnly, true);
            break;

        case HelixMode::height_turns_growth:
            // primary input:
            Height.setStatus(App::Property::ReadOnly, false);
            Turns.setStatus(App::Property::ReadOnly, false);
            Growth.setStatus(App::Property::ReadOnly, false);
            // derived props:
            Pitch.setStatus(App::Property::ReadOnly, true);
            Angle.setStatus(App::Property::ReadOnly, true);
            break;

        default:
            Pitch.setStatus(App::Property::ReadOnly, false);
            Height.setStatus(App::Property::ReadOnly, false);
            Turns.setStatus(App::Property::ReadOnly, false);
            Angle.setStatus(App::Property::ReadOnly, false);
            Growth.setStatus(App::Property::ReadOnly, false);
            break;
    }
}

PROPERTY_SOURCE(PartDesign::AdditiveHelix, PartDesign::Helix)
AdditiveHelix::AdditiveHelix()
{
    addSubType = Additive;
    Outside.setStatus(App::Property::Hidden, true);
}

PROPERTY_SOURCE(PartDesign::SubtractiveHelix, PartDesign::Helix)
SubtractiveHelix::SubtractiveHelix()
{
    addSubType = Subtractive;
    Outside.setStatus(App::Property::Hidden, false);
}