docs: function WorldRenderer(params) {
    this.init_(params.hideFullscreenButton);
  
    this.sphereRenderer = new SphereRenderer(this.scene);
    this.hotspotRenderer = new HotspotRenderer(this);
    this.hotspotRenderer.on('focus', this.onHotspotFocus_.bind(this));
    this.hotspotRenderer.on('blur', this.onHotspotBlur_.bind(this));
    this.reticleRenderer = new ReticleRenderer(this.camera);
  
    // Get the VR Display as soon as we initialize.
    navigator.getVRDisplays().then(function(displays) {
      if (displays.length > 0) {
        this.vrDisplay = displays[0];
      }
    }.bind(this));
  
  }