code: function () {
      var scene = this.el.sceneEl;
      this.setupMouseControls();
      this.setupHMDControls();
      this.attachEventListeners();
      scene.addBehavior(this);
      this.previousPosition = new THREE.Vector3();
      this.deltaPosition = new THREE.Vector3();
    }
docs: Called once when component is attached. Generally for initial setup.