Changed the textures again to give a better look (I'm using some Minecraft textures for now, but since this is a tutorial, I'm sure it's fine). Also optimized the floor rendering a little bit, but it's still far from perfect.
I changed the textures, and (more importantly) added ground rendering. The algorithm needs a lot of optimization, but it works correctly at least.
Porting to Rust a Python tutorial for creating a 3D game made by StanislavPetrovV, here's the Youtube link.
Caution! This is a work in progress, I have migrated it to Tetra (highly recommend this engine).
In any case, this project is only intented as a learning experience, for me and (I hope) for a few other people, if I manage to finish it.