WHAT IS THIS?
This is a SceneKit project that gives a concrete example as to how to create geometry; either procedurally (with a Perlin noise generator), or by creating a mesh from a 2D (non-transparent) image. Lots of room for improvement, but it's a start!
Many thanks go to the following people, without whom I'd never have got this far with SceneKit:
Jeff LaMarche, Tom Irving, Wade Tregaskis, and Thomas Goossens