Since a few months now, GZDoom supports PBR materials. Some dedicated modders thought it might be a good idea to generate normal/roughness/metallic/ao maps for the good old classic doom textures. First I thought "Can this look good?" - well, it really does. The current state can be found at the development thread at Doomworld and I really hope that these people get the rest pulled of. It feels very modern and still gives you this slight retro-look that we all love so much.