alt Hacker NewsFirst of all, DOOM isn’t raycasted. Second of all it’s 3D in the sense that all objects have xyz coordinates and can move in that space. You can miss the monsters by having a rocket go over their heads. The main limitation is that the levels couldn’t have more than one ‘room’ per vertical space.
The rendering can still be implemented as polygons (making it true 3D rendering) whilst still maintaining the same level-based limitations, as we can see with DOOM 64.
Yes, Doom renders walls in a way that is broadly similar to to how contemporary GPUs work. Doom sorts the walls in view space via the BSP tree, transforms them to screen space, breaks them into non-overlapping spans of screen columns, and then fills each column’s pixels with the wall’s textures. The floor and the sky are not geometry.