Hey, this paper from Hansmeyer helped drive.google.com/file/d/0By8IbGB-rwtrS1M3U09rZGRVZmxJMEJ3RTN3V0h1dDJvS1VB/view?usp=sharing
It’s essentially a catmull clark subdivision with extra displacement added to the newly created vertices.
The fun part was to implement the Catmull Clark subdivisions in a vex. I would share it here but I don’t have it, it’s at Imageworks.