nction initGUI() {
      var gui = new dat.GUI( { width: 250 } );
      var dirConfig = lights.directional.direction;
      var direction = {
        x: dirConfig[0],
        y: dirConfig[1],
        z: dirConfig[2],
      };
      var folder = gui.addFolder('direction');
      folder.open();
      var xCtrl = folder.add(direction, 'x', -1, 1, 0.1);
      var yCtrl = folder.add(direction, 'y', -1, 1, 0.1);
      var zCtrl = folder.add(direction, 'z', -1, 1, 0.1);

      xCtrl.onChange(function () {
        