I forked Stephen M. Cameron’s C port of Kurt Spencer’s open simplex noise while on the train to make it play nicely with Visual C++, which while it’s reasonably up to date with C++ is definitely stuck in the last century when it comes to C (it’s still shy of C99). I had a go at making of it ANSI C friendly too while I was there. The repo is here : Open Simplex Github fork.

EDIT : Changes now pushed up to main repository.