The interference node group is mostly adapted from Pruster’s own OSL interference script found in this Blenderartists thread: https://blenderartists.org/forum/showthread.php?403299-UPDATE-v1-6-Cycles-PBR-thin-film-interference-and-metals
The interference node group is mostly adapted from Pruster’s own OSL interference script found in this Blenderartists thread: https://blenderartists.org/forum/showthread.php?403299-UPDATE-v1-6-Cycles-PBR-thin-film-interference-and-metals