/*---------------------------------------------------------------------------*\
  =========                 |
  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
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    \\  /    A nd           | Copyright (C) 2011-2024 OpenFOAM Foundation
     \\/     M anipulation  |
-------------------------------------------------------------------------------
License
    This file is part of OpenFOAM.

    OpenFOAM is free software: you can redistribute it and/or modify it
    under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

    OpenFOAM 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 General Public License
    for more details.

    You should have received a copy of the GNU General Public License
    along with OpenFOAM.  If not, see <http://www.gnu.org/licenses/>.

Application
    surfaceLambdaMuSmooth

Description
    Smooths a surface using lambda/mu smoothing.

    To get laplacian smoothing, set lambda to the relaxation factor and mu to
    zero.

    Provide an edgeMesh file containing points that are not to be moved during
    smoothing in order to preserve features.

    lambda/mu smoothing: G. Taubin, IBM Research report Rc-19923 (02/01/95)
    "A signal processing approach to fair surface design"

\*---------------------------------------------------------------------------*/

#include "argList.H"
#include "boundBox.H"
#include "edgeMesh.H"
#include "matchPoints.H"
#include "MeshedSurfaces.H"

using namespace Foam;

// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

tmp<pointField> avg
(
    const meshedSurface& s,
    const PackedBoolList& fixedPoints
)
{
    const labelListList& pointEdges = s.pointEdges();

    tmp<pointField> tavg(new pointField(s.nPoints(), Zero));
    pointField& avg = tavg.ref();

    forAll(pointEdges, vertI)
    {
        vector& avgPos = avg[vertI];

        if (fixedPoints[vertI])
        {
            avgPos = s.localPoints()[vertI];
        }
        else
        {
            const labelList& pEdges = pointEdges[vertI];

            forAll(pEdges, myEdgeI)
            {
                const edge& e = s.edges()[pEdges[myEdgeI]];

                label otherVertI = e.otherVertex(vertI);

                avgPos += s.localPoints()[otherVertI];
            }

            avgPos /= pEdges.size();
        }
    }

    return tavg;
}


void getFixedPoints
(
    const edgeMesh& feMesh,
    const pointField& points,
    PackedBoolList& fixedPoints
)
{
    scalarList matchDistance(feMesh.points().size(), 1e-1);
    labelList from0To1;

    bool matchedAll = matchPoints
    (
        feMesh.points(),
        points,
        matchDistance,
        false,
        from0To1
    );

    if (!matchedAll)
    {
        WarningInFunction
            << "Did not match all feature points to points on the surface"
            << endl;
    }

    forAll(from0To1, fpI)
    {
        if (from0To1[fpI] != -1)
        {
            fixedPoints[from0To1[fpI]] = true;
        }
    }
}


// Main program:

int main(int argc, char *argv[])
{
    #include "removeCaseOptions.H"

    argList::validOptions.clear();
    argList::validArgs.append("surface file");
    argList::validArgs.append("output surface file");
    argList::validArgs.append("lambda (0..1)");
    argList::validArgs.append("mu (0..1)");
    argList::validArgs.append("iterations");
    argList::addOption
    (
        "featureFile",
        "fix points from a file containing feature points and edges"
    );
    argList args(argc, argv);

    const fileName surfFileName = args[1];
    const fileName outFileName = args[2];
    const scalar lambda = args.argRead<scalar>(3);
    const scalar mu = args.argRead<scalar>(4);
    const label  iters = args.argRead<label>(5);

    if (lambda < 0 || lambda > 1)
    {
        FatalErrorInFunction
            << lambda << endl
            << "0: no change   1: move vertices to average of neighbours"
            << exit(FatalError);
    }
    if (mu < 0 || mu > 1)
    {
        FatalErrorInFunction
            << mu << endl
            << "0: no change   1: move vertices to average of neighbours"
            << exit(FatalError);
    }

    Info<< "lambda      : " << lambda << nl
        << "mu          : " << mu << nl
        << "Iters       : " << iters << nl
        << "Reading surface from " << surfFileName << " ..." << endl;

    meshedSurface surf1(surfFileName);

    Info<< "Faces       : " << surf1.size() << nl
        << "Vertices    : " << surf1.nPoints() << nl
        << "Bounding Box: " << boundBox(surf1.localPoints()) << endl;

    PackedBoolList fixedPoints(surf1.localPoints().size(), false);

    if (args.optionFound("featureFile"))
    {
        const fileName featureFileName(args.option("featureFile"));
        Info<< "Reading features from " << featureFileName << " ..." << endl;

        edgeMesh feMesh(featureFileName);

        getFixedPoints(feMesh, surf1.localPoints(), fixedPoints);

        Info<< "Number of fixed points on surface = " << fixedPoints.count()
            << endl;
    }

    pointField newPoints(surf1.localPoints());

    for (label iter = 0; iter < iters; iter++)
    {
        // Lambda
        {
            pointField newLocalPoints
            (
                (1 - lambda)*surf1.localPoints()
              + lambda*avg(surf1, fixedPoints)
            );

            pointField newPoints(surf1.points());
            UIndirectList<point>(newPoints, surf1.meshPoints()) =
                newLocalPoints;

            surf1.setPoints(newPoints);
        }

        // Mu
        if (mu != 0)
        {
            pointField newLocalPoints
            (
                (1 + mu)*surf1.localPoints()
              - mu*avg(surf1, fixedPoints)
            );

            pointField newPoints(surf1.points());
            UIndirectList<point>(newPoints, surf1.meshPoints()) =
                newLocalPoints;

            surf1.setPoints(newPoints);
        }
    }

    Info<< "Writing surface to " << outFileName << " ..." << endl;
    surf1.write(outFileName);

    Info<< "End\n" << endl;

    return 0;
}


// ************************************************************************* //
