Originally released in August last year, Doom Remake 4 is a huge mod compilation for the original Doom that basically turns it into a modern first-person shooter. In addition to turning the old sprite-based items into full 3D (everything from objects to enemies), it introduces new HD textures with physically-based rendering, meaning surfaces will interact with lighting.
Meanwhile, enemy corpses disassemble (ie you can shoot them into bits) and weapons have 3D models, but otherwise the game is completely faithful to the original: no tweaks have been made to the maps, and the weapons function the same.
A new Experimental Edition of the mod was issued earlier today, adding a new texture lights script resulting in more impressive physically-based rendering (ie shinier and more responsive reflections). According to modder vasyan777, who oversees the mod, this new edition has been released separately because it's "quite resource hungry".
Whatever the case, it's definitely worth a look, even if you opt for the non-Experimental version. There's a video of the Experimental Edition in action below. Thanks to DSO Gaming for the heads up