type.getLengthScale = function()    { return 1.0; }
Scene.prototype.getMinLengthScale = function() { return 1.0e-4 * this.getLengthScale(); }
Scene.prototype.getMaxLengthScale = function() { return 5.0e2 * this.getLengthScale(); }

//Scene.prototype.envMap = function()
//{ return 'https://portsmouth.github.io/envmaps/fin4_Bg.jpg'; }

Scene.prototype.initGui = function(gui)
{
    this.typeItem = gui.getSceneFolder().add(this.par, 'n', this.par.n_options);
    this.typeItem.onChange( function(value) { snelly.