t scene = new Scene();
      let scale = 1;
      let scale_down = true;
      let useLayerCheckbox = document.getElementById('useLayer');
      let useLayer = false;
      // layer support
      let xrGLFactory = null;
      let xrFramebuffer = null;
      let proj_layer = null;
      let count = true;

      scene.addNode(new Gltf2Node({url: 'media/gltf/space/space.gltf'}));
      scene.addNode(new SkyboxNode({url: 'media/textures/milky-way-4k.png'}));

      function initXR() {
        xrButton = new Web