getFacadesAtEvent(e, filterFn) {
    throw new Error('getFacadesAtEvent: no impl')
  }
@abstract
Given a pointer-related Event, find and return all facade objects that are intersected
by that event. If any hits are found, this should return an array of objects that contain
at least `facade` and `distance` properties. Any additional properties will be exposed to
event listeners on the synthetic event object as an `intersection` property.
@param {Event} e
@param {Function} [filterFn]
@return {Array<{facade, distance, ?distanceBias, ...}>|null}