Viking Helmet Horns - Cracked Horn

For World Book Day my oldest wants to dress up as Hiccup from "How to Train Your Dragon" and so we needed a horned helmet. We found http://www.thingiverse.com/thing:692930 (which was brilliant) but we needed one of the horns to be broken so in this remix we subtracted a noise surface generated in Processing and OpenScad to make it look cracked at the end.