data/src/sampling/sampledSurface/sampledThresholdCellFaces/thresholdCellFaces.C

/*---------------------------------------------------------------------------*\
  =========                 |
  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
   \\    /   O peration     | Website:  https://openfoam.org
    \\  /    A nd           | Copyright (C) 2011-2026 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/>.

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

#include "thresholdCellFaces.H"
#include "emptyPolyPatch.H"
#include "processorPolyPatch.H"
#include "polygonTriangulate.H"

// * * * * * * * * * * * * * * Static Data Members * * * * * * * * * * * * * //

namespace Foam
{
    defineTypeNameAndDebug(thresholdCellFaces, 0);
}


// * * * * * * * * * * * * * Private Member Functions  * * * * * * * * * * * //

void Foam::thresholdCellFaces::calculate
(
    const scalarField& field,
    const scalar lowerThreshold,
    const scalar upperThreshold,
    const bool triangulate
)
{
    const labelList& own = mesh_.faceOwner();
    const labelList& nei = mesh_.faceNeighbour();

    const faceList& origFaces = mesh_.faces();
    const pointField& origPoints = mesh_.points();

    const polyBoundaryMesh& bMesh = mesh_.boundary();


    surfZoneList surfZones(bMesh.size()+1);

    surfZones[0] = surfZone
    (
        "internalMesh",
        0,  // size
        0,  // start
        0   // index
    );

    forAll(bMesh, patchi)
    {
        surfZones[patchi+1] = surfZone
        (
            bMesh[patchi].name(),
            0,        // size
            0,        // start
            patchi+1  // index
        );
    }


    label nFaces = 0;
    label nPoints = 0;


    meshCells_.clear();

    DynamicList<face>  surfFaces(0.5 * mesh_.nFaces());
    DynamicList<label> surfCells(surfFaces.size());

    labelList oldToNewPoints(origPoints.size(), -1);

    // Create a triangulation engine
    polygonTriangulate triEngine;

    // internal faces only
    for (label facei = 0; facei < mesh_.nInternalFaces(); ++facei)
    {
        int side = 0;

        // check lowerThreshold
        if (field[own[facei]] > lowerThreshold)
        {
            if (field[nei[facei]] < lowerThreshold)
            {
                side = +1;
            }
        }
        else if (field[nei[facei]] > lowerThreshold)
        {
            side = -1;
        }

        // check upperThreshold
        if (field[own[facei]] < upperThreshold)
        {
            if (field[nei[facei]] > upperThreshold)
            {
                side = +1;
            }
        }
        else if (field[nei[facei]] < upperThreshold)
        {
            side = -1;
        }


        if (side)
        {
            const face& f = origFaces[facei];

            forAll(f, fp)
            {
                if (oldToNewPoints[f[fp]] == -1)
                {
                    oldToNewPoints[f[fp]] = nPoints++;
                }
            }


            label cellId;
            face  surfFace;

            if (side > 0)
            {
                surfFace = f;
                cellId = own[facei];
            }
            else
            {
                surfFace = f.reverseFace();
                cellId = nei[facei];
            }


            if (triangulate)
            {
                triEngine.triangulate
                (
                    UIndirectList<point>(origPoints, surfFace)
                );
                forAll(triEngine.triPoints(), i)
                {
                    surfFaces.append(triEngine.triPoints(i, surfFace));
                    surfCells.append(cellId);
                }
            }
            else
            {
                surfFaces.append(surfFace);
                surfCells.append(cellId);
            }
        }
    }

    surfZones[0].size() = surfFaces.size();


    // nothing special for processor patches?
    forAll(bMesh, patchi)
    {
        const polyPatch& p = bMesh[patchi];
        surfZone& zone = surfZones[patchi+1];

        zone.start() = nFaces;

        if
        (
            isA<emptyPolyPatch>(p)
         || (Pstream::parRun() && isA<processorPolyPatch>(p))
        )
        {
            continue;
        }

        label facei = p.start();

        // patch faces
        forAll(p, localFacei)
        {
            if
            (
                field[own[facei]] > lowerThreshold
             && field[own[facei]] < upperThreshold
            )
            {
                const face& f = origFaces[facei];
                forAll(f, fp)
                {
                    if (oldToNewPoints[f[fp]] == -1)
                    {
                        oldToNewPoints[f[fp]] = nPoints++;
                    }
                }

                label cellId = own[facei];

                if (triangulate)
                {
                    triEngine.triangulate
                    (
                        UIndirectList<point>(origPoints, f)
                    );
                    forAll(triEngine.triPoints(), i)
                    {
                        surfFaces.append(triEngine.triPoints(i, f));
                        surfCells.append(cellId);
                    }
                }
                else
                {
                    surfFaces.append(f);
                    surfCells.append(cellId);
                }
            }

            ++facei;
        }

        zone.size() = surfFaces.size() - zone.start();
    }


    surfFaces.shrink();
    surfCells.shrink();

    // renumber
    forAll(surfFaces, facei)
    {
        inplaceRenumber(oldToNewPoints, surfFaces[facei]);
    }


    pointField surfPoints(nPoints);
    nPoints = 0;
    forAll(oldToNewPoints, pointi)
    {
        if (oldToNewPoints[pointi] >= 0)
        {
            surfPoints[oldToNewPoints[pointi]] = origPoints[pointi];
            nPoints++;
        }
    }
    surfPoints.setSize(nPoints);

    this->storedPoints().transfer(surfPoints);
    this->storedFaces().transfer(surfFaces);
    this->storedZones().transfer(surfZones);

    meshCells_.transfer(surfCells);
}


// * * * * * * * * * * * * * * * * Constructors  * * * * * * * * * * * * * * //

Foam::thresholdCellFaces::thresholdCellFaces
(
    const polyMesh& mesh,
    const scalarField& field,
    const scalar lowerThreshold,
    const scalar upperThreshold,
    const bool triangulate
)
:
    mesh_(mesh)
{

    if (lowerThreshold > upperThreshold)
    {
        WarningInFunction
            << lowerThreshold << " > " << upperThreshold << endl;
    }

    calculate(field, lowerThreshold, upperThreshold, triangulate);
}


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