void gsWriteParaviewMultiTPgrid(gsMatrix<T> const& points,
                                std::map<std::string, gsMatrix<T> >& data,
                                const gsVector<index_t> & np,
                                std::string const & fn)
{
    const int n = points.rows();

    std::string mfn(fn);
    mfn.append(".vts");
    std::ofstream file(mfn.c_str());
    file << std::fixed; // no exponents
    file << std::setprecision (PLOT_PRECISION);

    file <<"<?xml version=\"1.0\"?>\n";
    file <<"<VTKFile type=\"StructuredGrid\" version=\"0.1\">\n";
    file <<"<StructuredGrid WholeExtent=\"0 "<< np(0)-1<<" 0 "<<np(1)-1<<" 0 "
         << (np.size()>2 ? np(2)-1 : 0) <<"\">\n";
    file <<"<Piece Extent=\"0 "<< np(0)-1<<" 0 "<<np(1)-1<<" 0 "
         << (np.size()>2 ? np(2)-1 : 0) <<"\">\n";

    file <<"<PointData>\n";
    for (typename std::map<std::string, gsMatrix<T> >::iterator it = data.begin(); it != data.end(); it++)
    {
        file <<"<DataArray type=\"Float32\" Name=\""<< it->first <<"\" format=\"ascii\" NumberOfComponents=\""<< ( it->second.rows()==1 ? 1 : 3) <<"\">\n";
        if ( it->second.rows()==1 )
            for ( index_t j=0; j<it->second.cols(); ++j)
                file<< it->second.at(j) <<" ";
        else
        {
            for ( index_t j=0; j<it->second.cols(); ++j)
            {
                for ( index_t i=0; i!=it->second.rows(); ++i)
                    file<< it->second(i,j) <<" ";
                for ( index_t i=it->second.rows(); i<3; ++i)
                    file<<"0 ";
            }
        }
        file <<"</DataArray>\n";
    }
    file <<"</PointData>\n";
    file <<"<Points>\n";
    file <<"<DataArray type=\"Float32\" NumberOfComponents=\"3\">\n";
    for ( index_t j=0; j<points.cols(); ++j)
    {
        for ( index_t i=0; i!=n; ++i)
            file<< points(i,j) <<" ";
        for ( index_t i=n; i<3; ++i)
            file<<"0 ";
    }
    file <<"</DataArray>\n";
    file <<"</Points>\n";
    file <<"</Piece>\n";
    file <<"</StructuredGrid>\n";
    file <<"</VTKFile>\n";

    file.close();
}