Function smoothRegionBoundary

source/MRMesh/MRMeshRelax.cpp:307–432

}

void smoothRegionBoundary( Mesh & mesh, const FaceBitSet & regionFaces, int numIters )
{
    MR_TIMER;
    assert( numIters > 0 );
    if ( !regionFaces.any() || numIters <= 0 )
        return;

    // value 1 for out-of-region vertices
    VertScalars scalarField( mesh.topology.vertSize(), 1 );

    const auto regionVerts = getIncidentVerts( mesh.topology, regionFaces );
    // value -1 for in-region vertices
    for( auto v : regionVerts )
        scalarField[v] = -1;

    /// free vertices must have both in-region and out-of-region neighbor faces
    VertBitSet freeVerts = getIncidentVerts( mesh.topology, mesh.topology.getValidFaces() - regionFaces ) & regionVerts;

    for ( const auto & cc : MeshComponents::getAllComponentsVerts( mesh ) )
    {
        auto freeCC = cc & freeVerts;
        auto numfree = freeCC.count();
        auto numCC = cc.count();
        assert( numfree <= numCC );
        if ( numfree <= 0 )
            continue; // too small connected component
        if ( numfree < numCC )
            continue; // at least one fixed vertex in the component

        // all component vertices are free, just fix them all (to -1) to avoid under-determined system of equations
        freeVerts -= cc;
    }

    // change topology: eliminate not boundary edges joining two boundary vertices
    for ( auto v : freeVerts )
    {
        mesh.topology.flipEdgesOut( v, [&]( EdgeId e )
        {
            assert( mesh.topology.org( e ) == v );
            if ( regionFaces.test( mesh.topology.left( e ) ) != regionFaces.test( mesh.topology.right( e ) ) )
                return false;

            auto c = mesh.topology.dest( e );

            if ( !freeVerts.test( c ) )
                return false;

            auto b = mesh.topology.dest( mesh.topology.prev( e ) );
            auto d = mesh.topology.dest( mesh.topology.next( e ) );
            if ( freeVerts.test( b ) && freeVerts.test( c ) )
              return false;

            if ( mesh.topology.findEdge( d, b ) )
                return false; // multiple edges between b and d will appear

            auto ap = mesh.points[v];
            auto bp = mesh.points[b];
            auto cp = mesh.points[c];