C++ (Cpp) Seam::push_back Examples

Example #1

File: Mesh_cutting_parameterization.cpp Project: FMX/CGAL

// If the mesh is a topological disk, extract its longest border,
// else compute a very simple cut to make it homeomorphic to a disk.
// Return the border of this region (empty on error)
//
// CAUTION: this cutting algorithm is very naive. Write your own!
static Seam cut_mesh(Parameterization_polyhedron_adaptor& mesh_adaptor)
{
    // Helper class to compute genus or extract borders
    typedef CGAL::Parameterization_mesh_feature_extractor<Parameterization_polyhedron_adaptor>
                                            Mesh_feature_extractor;

    Seam seam;              // returned list

    // Get reference to Polyhedron_3 mesh
    Polyhedron& mesh = mesh_adaptor.get_adapted_mesh();

    // Extract mesh borders and compute genus
    Mesh_feature_extractor feature_extractor(mesh_adaptor);
    int nb_borders = feature_extractor.get_nb_borders();
    int genus = feature_extractor.get_genus();

    // If mesh is a topological disk
    if (genus == 0 && nb_borders > 0)
    {
        // Pick the longest border
        seam = feature_extractor.get_longest_border();
    }
    else // if mesh is *not* a topological disk, create a virtual cut
    {
        const int CUT_LENGTH = 6;

        // Build consecutive halfedges array
        Polyhedron::Halfedge_handle seam_halfedges[CUT_LENGTH];
        seam_halfedges[0] = mesh.halfedges_begin();
        if (seam_halfedges[0] == NULL)
            return seam;                    // return empty list
        int i;
        for (i=1; i<CUT_LENGTH; i++)
        {
            seam_halfedges[i] = seam_halfedges[i-1]->next()->opposite()->next();
            if (seam_halfedges[i] == NULL)
                return seam;                // return empty list
        }

        // Convert halfedges array to two-ways vertices list
        for (i=0; i<CUT_LENGTH; i++)
            seam.push_back(seam_halfedges[i]->vertex());
        for (i=CUT_LENGTH-1; i>=0; i--)
            seam.push_back(seam_halfedges[i]->opposite()->vertex());
    }

    return seam;
}

Example #2

File: polyhedron_ex_parameterization.cpp Project: BijanZarif/mshr

// Cut the mesh to make it homeomorphic to a disk
// or extract a region homeomorphic to a disc.
// Return the border of this region (empty on error)
//
// CAUTION:
// This method is provided "as is". It is very buggy and simply part of this example.
// Developers using this package should implement a more robust cut algorithm!
static Seam cut_mesh(Parameterization_polyhedron_adaptor& mesh_adaptor)
{
    // Helper class to compute genus or extract borders
    typedef CGAL::Parameterization_mesh_feature_extractor<Parameterization_polyhedron_adaptor_ex>
                                            Mesh_feature_extractor;
    typedef Mesh_cutter::Backbone           Backbone;

    Seam seam;              // returned list

    // Get refererence to Polyhedron_3 mesh
    Polyhedron& mesh = mesh_adaptor.get_adapted_mesh();

    // Extract mesh borders and compute genus
    Mesh_feature_extractor feature_extractor(mesh_adaptor);
    int nb_borders = feature_extractor.get_nb_borders();
    int genus = feature_extractor.get_genus();

    // If mesh is a topological disk
    if (genus == 0 && nb_borders > 0)
    {
        // Pick the longest border
        seam = feature_extractor.get_longest_border();
    }
    else // if mesh is *not* a topological disk, create a virtual cut
    {
        Backbone seamingBackbone;           // result of cutting
        Backbone::iterator he;

        // Compute a cutting path that makes the mesh a "virtual" topological disk
        mesh.compute_facet_centers();
        Mesh_cutter cutter(mesh);
        if (genus == 0)
        {
            // no border, we need to cut the mesh
            assert (nb_borders == 0);
            cutter.cut(seamingBackbone);    // simple cut
        }
        else // genus > 0 -> cut the mesh
        {
            cutter.cut_genus(seamingBackbone);
        }

        // The Mesh_cutter class is quite buggy
        // => we check that seamingBackbone is valid
        //
        // 1) Check that seamingBackbone is not empty
        if (seamingBackbone.begin() == seamingBackbone.end())
            return seam;                    // return empty list
        //
        // 2) Check that seamingBackbone is a loop and
        //    count occurences of seam halfedges
        mesh.tag_halfedges(0);              // Reset counters
        for (he = seamingBackbone.begin(); he != seamingBackbone.end(); he++)
        {
            // Get next halfedge iterator (looping)
            Backbone::iterator next_he = he;
            next_he++;
            if (next_he == seamingBackbone.end())
                next_he = seamingBackbone.begin();

            // Check that seamingBackbone is a loop: check that
            // end of current HE == start of next one
            if ((*he)->vertex() != (*next_he)->opposite()->vertex())
                return seam;                // return empty list

            // Increment counter (in "tag" field) of seam halfedges
            (*he)->tag( (*he)->tag()+1 );
        }
        //
        // 3) check that the seamingBackbone is a two-way list
        for (he = seamingBackbone.begin(); he != seamingBackbone.end(); he++)
        {
            // Counter of halfedge and opposite halfedge must be 1
            if ((*he)->tag() != 1 || (*he)->opposite()->tag() != 1)
                return seam;                // return empty list
        }

        // Convert list of halfedges to a list of vertices
        for (he = seamingBackbone.begin(); he != seamingBackbone.end(); he++)
            seam.push_back((*he)->vertex());
    }

    return seam;
}