It really seems like their smoke processing is just removing/re-adding cubes into the volumetric model, then using the shape of the cubes to draw "a cloud". It

It really seems like their smoke processing is just removing/re-adding cubes into the volumetric model, then using the shape of the cubes to draw "a cloud". It looks more like a marshmallow than a cloud of smoke, to me. It doesn't seem like they model air movement, at all, and I don't see how to get realistic smoke without some concept of wind.