Awesome
Wavefront OBJ/MTL Highlighting in Atom
This package adds syntax highlighting for Wavefront OBJ files (.obj),
as well as its complementary format for describing surface materials (.mtl).
Format reference
The original Wavefront OBJ specification survives in the form of a PDF file circulated between various third-party sources. To help preserve a moribund file-format, I've included copies of original specifications with this repo:
The Library of Congress also has an excellent article detailing the format's syntax and background, although some of its inline citations have succumbed to link rot.