/vr/ - Retro Games

>>3179443
Because there is nothing behind the lower. The middle is where it's at. Consider doom mapping like gluing boxes together. The sides of the box are the middle texture, the bottom/top are floor ceiling. Consider pic related. I've made red a mid texture. If I were to put a room to the right of that box, connecting at the red texture, the red texture would be approximately infinitely thin. It's a line(def) after all, it has no thickness.

Consider now the orange bit under the middle box. That is the lower texture you will see. (assuming it has the same lower texture on all its linedefs and sides). If you made it transparent, it would try to draw what is right behind it, which you can interpret as either
>"void"
>More of the same (infinite thick model)

This is just how I try to intuitively understand it. Don't assume this is actually how doom works. It probably isn't. But what the other anons said, 3D floors can "fix this", because then you can sort of stack sectors.