s  = snelly.getControls();
    let materials = snelly.getMaterials();
        
    this.par = {};
    this.par.n_options = ['1', '2', '3', '4'];
    this.par.lm_options = [       '0,0', 
                           '1,1', '1,0', '1,-1', 
                    '2,2', '2,1', '2,0', '2,-1', '2,-2',
             '3,3', '3,2', '3,1', '2,0', '3,-1', '3,-2', '3,-3' ]
    this.par.n = 4;
    this.par.lm = '3,2';

    this.par.R = 1.0;
    this.par.background = 0.1;

    snelly.showGUI(true);

    /** Material settings