Modeled with Symvol for Rhino: The state-of-art of 3D modeling for AM. It will never fail in deliver a perfect water tight model. No matter the complexity of the geometry. 

"Symvol™ is a volumetric modeling system which makes using it more like working with a malleable material, such as clay or metal, as opposed to existing modeling systems which seem more like working with a collection of paper sheets glued together. With Symvol, whatever is done during modeling, the volume created is always a valid solid object - never any cracks and other surface issues."

It's just a simple example - the power of Symvol is just limited by your imagination.