code: @Override
  	public Point3d getPivot() {
  		Point3d pivot = this.cachedPivot == null ? null : this.cachedPivot.get();
  		if (pivot==null) {
  			pivot = getProjection(0., 0., 0.);
  			this.cachedPivot = new WeakReference<>(pivot);
  		}
  		return pivot;
  	}
docs: Replies the pivot point around which the rotation must be done.
  
  @return a reference on the buffered pivot point.