[pjc50]

Not to mention that it's a completely different rendering algorithm that produces different scenes: this is a "true 3D" geometry converter, while the original Carmack code was a "2.5D" rasteriser. That's why original Doom couldn't look up or down and has only one "vanishing point", whereas you can clearly see non-parallel vertical features in the modern screenshots.

Edit: the original renderer is actually very readable, https://github.com/id-Software/DOOM/blob/77735c3ff0772609e9c...

I don't see a great scope for auto-vectorisation etc there. You could write a new 2.5D renderer which assumed its availability, but that would be not quite directly comparable.