ve the
      // framebuffer cleared, so tracking loss means the scene will simply
      // disappear.
      if (pose) {
        let glLayer = session.renderState.baseLayer;

        // If we do have a valid pose, bind the WebGL layer's framebuffer,
        // which is where any content to be displayed on the XRDevice must be
        // rendered.
        gl.bindFramebuffer(gl.FRAMEBUFFER, glLayer.framebuffer);

        // Clear the framebuffer
        gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);

   