initThreeObject() {
    const obj = new Object3D()
    obj.isRenderable = false //trigger optimizations
    return obj
  }
Lifecycle method, called at constructor time, that creates and returns a Three.js `Object3D`
instance which will become the `threeObject` for this facade. This is a more ergonomic
alternative than overriding the constructor to pass the `threeObject` as a second argument
to the super() call. By default it creates a plain Object3D marked as non-renderable so it
is not added to the Three.js tree.
@return {Object3D}
@protected