data/src/meshTools/triSurface/booleanOps/surfaceIntersection/edgeIntersections.C

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

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

#include "edgeIntersections.H"
#include "triSurfaceSearch.H"
#include "labelPairLookup.H"
#include "OFstream.H"
#include "HashSet.H"
#include "triSurface.H"
#include "pointIndexHit.H"
#include "treeDataTriSurface.H"
#include "indexedOctree.H"
#include "meshTools.H"
#include "plane.H"
#include "randomGenerator.H"
#include "units.H"
#include "treeBoundBox.H"

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

namespace Foam
{
defineTypeNameAndDebug(edgeIntersections, 0);

scalar edgeIntersections::alignedCos_ = cos(degToRad(89.0));
}


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

void Foam::edgeIntersections::checkEdges(const triSurface& surf)
{
    const pointField& localPoints = surf.localPoints();
    const edgeList& edges = surf.edges();
    const labelListList& edgeFaces = surf.edgeFaces();

    treeBoundBox bb(localPoints);

    scalar minSize = small * bb.minDim();

    forAll(edges, edgeI)
    {
        const edge& e = edges[edgeI];

        scalar eMag = e.mag(localPoints);

        if (eMag < minSize)
        {
            WarningInFunction
                << "Edge " << edgeI << " vertices " << e
                << " coords:" << localPoints[e[0]] << ' '
                << localPoints[e[1]] << " is very small compared to bounding"
                << " box dimensions " << bb << endl
                << "This might lead to problems in intersection"
                << endl;
        }

        if (edgeFaces[edgeI].size() == 1)
        {
            WarningInFunction
                << "Edge " << edgeI << " vertices " << e
                << " coords:" << localPoints[e[0]] << ' '
                << localPoints[e[1]] << " has only one face connected to it:"
                << edgeFaces[edgeI] << endl
                << "This might lead to problems in intersection"
                << endl;
        }
    }
}


// Update intersections for selected edges.
void Foam::edgeIntersections::intersectEdges
(
    const triSurface& surf1,
    const pointField& points1,          // surf1 meshPoints (not localPoints!)
    const triSurfaceSearch& querySurf2,
    const scalarField& surf1PointTol,   // surf1 tolerance per point
    const labelList& edgeLabels
)
{
    const triSurface& surf2 = querySurf2.surface();
    const vectorField& normals2 = surf2.faceNormals();

    const labelList& meshPoints = surf1.meshPoints();

    if (debug)
    {
        Pout<< "Calculating intersection of " << edgeLabels.size() << " edges"
            << " out of " << surf1.nEdges() << " with " << surf2.size()
            << " triangles ..." << endl;
    }

    pointField start(edgeLabels.size());
    pointField end(edgeLabels.size());
    vectorField edgeDirs(edgeLabels.size());

    // Go through all edges, calculate intersections
    forAll(edgeLabels, i)
    {
        label edgeI = edgeLabels[i];

        if (debug)// && (i % 1000 == 0))
        {
            Pout<< "Intersecting edge " << edgeI << " with surface" << endl;
        }

        const edge& e = surf1.edges()[edgeI];

        const point& pStart = points1[meshPoints[e.start()]];
        const point& pEnd = points1[meshPoints[e.end()]];

        const vector eVec(pEnd - pStart);
        const vector n(eVec/(mag(eVec) + vSmall));

        // Start tracking somewhat before pStart and up to somewhat after p1.
        // Note that tolerances here are smaller than those used to classify
        // hit below.
        // This will cause this hit to be marked as degenerate and resolved
        // later on.
        start[i] = pStart - 0.5*surf1PointTol[e[0]]*n;
        end[i] = pEnd + 0.5*surf1PointTol[e[1]]*n;

        edgeDirs[i] = n;
    }

    List<List<pointIndexHit>> edgeIntersections;
    querySurf2.findLineAll
    (
        start,
        end,
        edgeIntersections
    );

    label nHits = 0;

    // Classify the hits
    forAll(edgeLabels, i)
    {
        const label edgeI = edgeLabels[i];

        labelList& intersectionTypes = classification_[edgeI];
        intersectionTypes.setSize(edgeIntersections[i].size(), -1);

        this->operator[](edgeI).transfer(edgeIntersections[i]);

        forAll(intersectionTypes, hitI)
        {
            const pointIndexHit& pHit = this->operator[](edgeI)[hitI];
            label& hitType = intersectionTypes[hitI];

            if (!pHit.hit())
            {
                continue;
            }

            const edge& e = surf1.edges()[edgeI];

            // Classify point on surface1 edge.
            if (mag(pHit.hitPoint() - start[i]) < surf1PointTol[e[0]])
            {
                // Intersection is close to edge start
                hitType = 0;
            }
            else if (mag(pHit.hitPoint() - end[i]) < surf1PointTol[e[1]])
            {
                // Intersection is close to edge end
                hitType = 1;
            }
            else if (mag(edgeDirs[i] & normals2[pHit.index()]) < alignedCos_)
            {
                // Edge is almost coplanar with the face

                Pout<< "Flat angle edge:" << edgeI
                    << " face:" << pHit.index()
                    << " cos:" << mag(edgeDirs[i] & normals2[pHit.index()])
                    << endl;

                hitType = 2;
            }

            if (debug)
            {
                Info<< "    hit " << pHit << " classify = " << hitType << endl;
            }

            nHits++;
        }
    }

    if (debug)
    {
        Pout<< "Found " << nHits << " intersections of edges with surface ..."
            << endl;
    }
}


// If edgeI intersections are close to endpoint of edge shift endpoints
// slightly along edge
// Updates
// - points1 with new endpoint position
// - affectedEdges with all edges affected by moving the point
// Returns true if changed anything.
bool Foam::edgeIntersections::inlinePerturb
(
    const triSurface& surf1,
    const scalarField& surf1PointTol,   // surf1 tolerance per point
    const label edgeI,
    randomGenerator& rndGen,
    pointField& points1,
    boolList& affectedEdges
) const
{
    bool hasPerturbed = false;

    // Check if edge close to endpoint. Note that we only have to check
    // the intersection closest to the edge endpoints (i.e. first and last in
    // edgeEdgs)

    const labelList& edgeEnds = classification_[edgeI];

    if (edgeEnds.size())
    {
        bool perturbStart = false;
        bool perturbEnd = false;

        // Check first intersection.
        if (edgeEnds.first() == 0)
        {
            perturbStart = true;
        }

        if (edgeEnds.last() == 1)
        {
            perturbEnd = true;
        }


        if (perturbStart || perturbEnd)
        {
            const edge& e = surf1.edges()[edgeI];

            label v0 = surf1.meshPoints()[e[0]];
            label v1 = surf1.meshPoints()[e[1]];

            vector eVec(points1[v1] - points1[v0]);
            vector n = eVec/mag(eVec);

            if (perturbStart)
            {
                // Perturb with something (hopefully) larger than tolerance.
                scalar t = 4.0*(rndGen.scalar01() - 0.5);
                points1[v0] += t*surf1PointTol[e[0]]*n;

                const labelList& pEdges = surf1.pointEdges()[e[0]];

                forAll(pEdges, i)
                {
                    affectedEdges[pEdges[i]] = true;
                }
            }
            if (perturbEnd)
            {
                // Perturb with something larger than tolerance.
                scalar t = 4.0*(rndGen.scalar01() - 0.5);
                points1[v1] += t*surf1PointTol[e[1]]*n;

                const labelList& pEdges = surf1.pointEdges()[e[1]];

                forAll(pEdges, i)
                {
                    affectedEdges[pEdges[i]] = true;
                }
            }
            hasPerturbed = true;
        }
    }

    return hasPerturbed;
}


// Perturb single edge endpoint when perpendicular to face
bool Foam::edgeIntersections::rotatePerturb
(
    const triSurface& surf1,
    const scalarField& surf1PointTol,   // surf1 tolerance per point
    const label edgeI,

    randomGenerator& rndGen,
    pointField& points1,
    boolList& affectedEdges
) const
{
    const labelList& meshPoints = surf1.meshPoints();

    const labelList& edgeEnds = classification_[edgeI];

    bool hasPerturbed = false;

    forAll(edgeEnds, i)
    {
        if (edgeEnds[i] == 2)
        {
            const edge& e = surf1.edges()[edgeI];

            // Endpoint to modify. Choose either start or end.
            label pointi = e[rndGen.sampleAB<label>(0, 2)];
            // label pointi = e[0];

            // Generate random vector slightly larger than tolerance.
            vector rndVec = rndGen.sample01<vector>() - vector(0.5, 0.5, 0.5);

            // Make sure rndVec only perp to edge
            vector n(points1[meshPoints[e[1]]] - points1[meshPoints[e[0]]]);
            scalar magN = mag(n) + vSmall;
            n /= magN;

            rndVec -= n*(n & rndVec);

            // Normalise
            rndVec /= mag(rndVec) + vSmall;

            // Scale to be moved by tolerance.
            rndVec *= 0.01*magN;

            Pout<< "rotating: shifting endpoint " << meshPoints[pointi]
                << " of edge:" << edgeI << " verts:"
                << points1[meshPoints[e[0]]] << ' '
                << points1[meshPoints[e[1]]]
                << " by " << rndVec
                << " tol:" << surf1PointTol[pointi] << endl;

            points1[meshPoints[pointi]] += rndVec;

            // Mark edges affected by change to point
            const labelList& pEdges = surf1.pointEdges()[pointi];

            forAll(pEdges, i)
            {
                affectedEdges[pEdges[i]] = true;
            }

            hasPerturbed = true;

            // Enough done for current edge; no need to test other intersections
            // of this edge.
            break;
        }
    }

    return hasPerturbed;
}


// Perturb edge when close to face
bool Foam::edgeIntersections::offsetPerturb
(
    const triSurface& surf1,
    const triSurface& surf2,
    const label edgeI,

    randomGenerator& rndGen,
    pointField& points1,
    boolList& affectedEdges
) const
{
    const labelList& meshPoints = surf1.meshPoints();

    const edge& e = surf1.edges()[edgeI];

    const List<pointIndexHit>& hits = operator[](edgeI);


    bool hasPerturbed = false;

    // For all hits on edge
    forAll(hits, i)
    {
        const pointIndexHit& pHit = hits[i];

        // Classify point on face of surface2
        label surf2Facei = pHit.index();

        const triSurface::FaceType& f2 = surf2.localFaces()[surf2Facei];
        const pointField& surf2Pts = surf2.localPoints();

        const point ctr = f2.centre(surf2Pts);

        label nearType, nearLabel;

        f2.nearestPointClassify(pHit.hitPoint(), surf2Pts, nearType, nearLabel);

        if (nearType == triPointRef::POINT || nearType == triPointRef::EDGE)
        {
            // Shift edge towards tri centre
            vector offset = 0.01*rndGen.scalar01()*(ctr - pHit.hitPoint());

            // shift e[0]
            points1[meshPoints[e[0]]] += offset;

            // Mark edges affected by change to e0
            const labelList& pEdges0 = surf1.pointEdges()[e[0]];

            forAll(pEdges0, i)
            {
                affectedEdges[pEdges0[i]] = true;
            }

            // shift e[1]
            points1[meshPoints[e[1]]] += offset;

            // Mark edges affected by change to e1
            const labelList& pEdges1 = surf1.pointEdges()[e[1]];

            forAll(pEdges1, i)
            {
                affectedEdges[pEdges1[i]] = true;
            }

            hasPerturbed = true;

            // No need to test any other hits on this edge
            break;
        }
    }

    return hasPerturbed;
}


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

// Construct null
Foam::edgeIntersections::edgeIntersections()
:
    List<List<pointIndexHit>>(),
    classification_()
{}


// Construct from surface and tolerance
Foam::edgeIntersections::edgeIntersections
(
    const triSurface& surf1,
    const triSurfaceSearch& query2,
    const scalarField& surf1PointTol
)
:
    List<List<pointIndexHit>>(surf1.nEdges()),
    classification_(surf1.nEdges())
{
    checkEdges(surf1);
    checkEdges(query2.surface());

    // Current set of edges to test
    labelList edgesToTest(surf1.nEdges());

    // Start off with all edges
    forAll(edgesToTest, i)
    {
        edgesToTest[i] = i;
    }

    // Determine intersections for edgesToTest
    intersectEdges
    (
        surf1,
        surf1.points(), // surf1 meshPoints (not localPoints!)
        query2,
        surf1PointTol,
        edgesToTest
    );
}


// Construct from components
Foam::edgeIntersections::edgeIntersections
(
    const List<List<pointIndexHit>>& intersections,
    const labelListList& classification
)
:
    List<List<pointIndexHit>>(intersections),
    classification_(classification)
{}


// * * * * * * * * * * * * * * * Static Functions  * * * * * * * * * * * * * //

Foam::scalarField Foam::edgeIntersections::minEdgeLength(const triSurface& surf)
{
    const pointField& localPoints = surf.localPoints();
    const labelListList& pointEdges = surf.pointEdges();
    const edgeList& edges = surf.edges();

    scalarField minLen(localPoints.size());

    forAll(minLen, pointi)
    {
        const labelList& pEdges = pointEdges[pointi];

        scalar minDist = great;

        forAll(pEdges, i)
        {
            minDist = min(minDist, edges[pEdges[i]].mag(localPoints));
        }

        minLen[pointi] = minDist;
    }
    return minLen;
}


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

Foam::label Foam::edgeIntersections::removeDegenerates
(
    const label nIters,
    const triSurface& surf1,
    const triSurfaceSearch& query2,
    const scalarField& surf1PointTol,
    pointField& points1
)
{
    const triSurface& surf2 = query2.surface();

    randomGenerator rndGen(356574);

    // Current set of edges to (re)test
    labelList edgesToTest(surf1.nEdges());

    // Start off with all edges
    forAll(edgesToTest, i)
    {
        edgesToTest[i] = i;
    }


    label iter = 0;

    for (; iter < nIters; iter++)
    {
        // Go through all edges to (re)test and perturb points if they are
        // degenerate hits. Mark off edges that need to be recalculated.

        boolList affectedEdges(surf1.nEdges(), false);
        label nShifted = 0;
        label nRotated = 0;
        label nOffset = 0;

        forAll(edgesToTest, i)
        {
            label edgeI = edgesToTest[i];

            // If edge not already marked for retesting
            if (!affectedEdges[edgeI])
            {
                // 1. Check edges close to endpoint and perturb if necessary.

                bool shiftedEdgeEndPoints =
                    inlinePerturb
                    (
                        surf1,
                        surf1PointTol,
                        edgeI,
                        rndGen,
                        points1,
                        affectedEdges
                    );

                nShifted += (shiftedEdgeEndPoints ? 1 : 0);

                if (!shiftedEdgeEndPoints)
                {
                    bool rotatedEdge =
                        rotatePerturb
                        (
                            surf1,
                            surf1PointTol,
                            edgeI,
                            rndGen,
                            points1,
                            affectedEdges
                        );

                    nRotated += (rotatedEdge ? 1 : 0);

                    if (!rotatedEdge)
                    {
                        // 2. we're sure now that the edge actually pierces the
                        // face. Now check the face for intersections close its
                        // points/edges

                        bool offsetEdgePoints =
                            offsetPerturb
                            (
                                surf1,
                                surf2,
                                edgeI,
                                rndGen,
                                points1,
                                affectedEdges
                            );

                        nOffset += (offsetEdgePoints ? 1 : 0);
                    }
                }
            }
        }

        if (debug)
        {
            Pout<< "Edges to test : " << nl
                << "    total:" << edgesToTest.size() << nl
                << "    resolved by:" << nl
                << "        shifting   : " << nShifted << nl
                << "        rotating   : " << nRotated << nl
                << "        offsetting : " << nOffset << nl
                << endl;
        }


        if (nShifted == 0 && nRotated == 0 && nOffset == 0)
        {
            // Nothing changed in current iteration. Current hit pattern is
            // without any degenerates.
            break;
        }

        // Repack affected edges
        labelList newEdgesToTest(surf1.nEdges());
        label newEdgeI = 0;

        forAll(affectedEdges, edgeI)
        {
            if (affectedEdges[edgeI])
            {
                newEdgesToTest[newEdgeI++] = edgeI;
            }
        }
        newEdgesToTest.setSize(newEdgeI);

        if (debug)
        {
            Pout<< "Edges to test:" << nl
                << "    was : " << edgesToTest.size() << nl
                << "    is  : " << newEdgesToTest.size() << nl
                << endl;
        }

        // Transfer and test.
        edgesToTest.transfer(newEdgesToTest);

        if (edgesToTest.empty())
        {
            FatalErrorInFunction << "oops" << abort(FatalError);
        }

        // Re intersect moved edges.
        intersectEdges
        (
            surf1,
            points1,          // surf1 meshPoints (not localPoints!)
            query2,
            surf1PointTol,
            edgesToTest
        );
    }

    return iter;
}


void Foam::edgeIntersections::merge
(
    const edgeIntersections& subInfo,
    const labelList& edgeMap,
    const labelList& faceMap,
    const bool merge
)
{
    forAll(subInfo, subI)
    {
        const List<pointIndexHit>& subHits = subInfo[subI];
        const labelList& subClass = subInfo.classification()[subI];

        label edgeI = edgeMap[subI];
        List<pointIndexHit>& intersections = operator[](edgeI);
        labelList& intersectionTypes = classification_[edgeI];

        // Count unique hits. Assume edge can hit face only once
        label sz = 0;
        if (merge)
        {
            sz = intersections.size();
        }

        label nNew = 0;
        forAll(subHits, i)
        {
            const pointIndexHit& subHit = subHits[i];

            bool foundFace = false;
            for (label interI = 0; interI < sz; interI++)
            {
                if (intersections[interI].index() == faceMap[subHit.index()])
                {
                    foundFace = true;
                    break;
                }
            }
            if (!foundFace)
            {
                nNew++;
            }
        }


        intersections.setSize(sz+nNew);
        intersectionTypes.setSize(sz+nNew);
        nNew = sz;

        forAll(subHits, i)
        {
            const pointIndexHit& subHit = subHits[i];

            bool foundFace = false;
            for (label interI = 0; interI < sz; interI++)
            {
                if (intersections[interI].index() == faceMap[subHit.index()])
                {
                    foundFace = true;
                    break;
                }
            }

            if (!foundFace)
            {
                intersections[nNew] = pointIndexHit
                (
                    subHit.hit(),
                    subHit.rawPoint(),
                    faceMap[subHit.index()]
                );
                intersectionTypes[nNew] = subClass[i];
                nNew++;
            }
        }
    }
}


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