code: function () {
      var self = this;
      var sceneEl = this.el.sceneEl;
  
      this.tickWorldBound = this.tickWorld.bind(this);
  
      // Wait for scene to load to initialize physics world.
      sceneEl.addEventListener('loaded', function () {
        if (!('physics-world' in sceneEl.components)) {
          console.warn('physics-world must be specified on scene for physics to work.');
        }
        var world = self.world = sceneEl.components['physics-world'].world;
        var body = self.body = self.getBody(self.el, self.data);
        world.add(body);
      });
    }
docs: TODO: Don't force physics-world to be on scene to allow for multiple physics worlds.