Function compareEdgeTrisIntersections

source/MRMesh/MRContoursCut.cpp:496–538

compare intersections of two triangles with one edge along that edge; returns Unknown only if both triangles share the same 3 vertices

/// compare intersections of two triangles with one edge along that edge;
/// returns Unknown only if both triangles share the same 3 vertices
CompareResult compareEdgeTrisIntersections( EdgeId intersectedEdge, const Mesh& mesh, const SortIntersectionsData& sortData,
    FaceId fl, FaceId fr )
{
    assert( fl != fr );

    const auto& otherTopology = sortData.otherMesh.topology;
    auto vsl = otherTopology.getTriVerts( fl );
    std::sort( vsl.begin(), vsl.end() );
    auto vsr = otherTopology.getTriVerts( fr );
    std::sort( vsr.begin(), vsr.end() );
    if ( vsl == vsr )
        return CompareResult::Unknown;

    VertId vo = mesh.topology.org( intersectedEdge );
    VertId vd = mesh.topology.dest( intersectedEdge );

    auto po = mesh.points[vo];
    auto pd = mesh.points[vd];

    if ( sortData.isOtherA )
    {
        vo += (int)sortData.meshAVertsNum;
        vd += (int)sortData.meshAVertsNum;
        if ( sortData.rigidB2A )
        {
            po = (*sortData.rigidB2A)( po );
            pd = (*sortData.rigidB2A)( pd );
        }
    }

    std::array<PreciseVertCoords, 8> preciseVerts
    {
        PreciseVertCoords{ vo, sortData.converter( po ) },
        PreciseVertCoords{ vd, sortData.converter( pd ) },
        preciseOtherVert( vsl[0], sortData ),
        preciseOtherVert( vsl[1], sortData ),
        preciseOtherVert( vsl[2], sortData ),
        preciseOtherVert( vsr[0], sortData ),
        preciseOtherVert( vsr[1], sortData ),
        preciseOtherVert( vsr[2], sortData )
    };
    return segmentIntersectionOrder( preciseVerts ) ? CompareResult::Less : CompareResult::Greater;
}

/// compare intersections of two triangles with one edge along that edge;
/// if both triangles share the same 3 vertices then goes along the contours to other intersection in hope to resolve the ambiguity