'Doom:' A Classic Game Postmortem

I still play Doom and Doom 2, I even list it as an interest in my HN profile. It's the perfect FPS, to me. There's still a reasonably active community making custom WADs. It's amazing what some people have come up with for this 20 year old series [1]. There's a ladder of difficulty in custom WADs that I've been working my way up over the years before finally throwing in the towel because of Scythe 2 Map 23 [2]. On a side note, John Romero and Tom Hall did an hour long post mortem on the design and development of the original Doom a couple years ago [3]. I found it interesting. [1]link [2]link [3]▶ this video

Yes, I played it at the time on both a 286 and a 386. You might be right, although you're describing an algorithm more like what Duke3d used rather than raycasting in that case. I was talking purely about raycasting. So it sounds like a misunderstanding on my part. It's true that Carmack has said several times, including in the readme to the source release of Wolf3d [0], that a BSP-based renderer might be faster than raycasting. He used a BSP tree based renderer for the SNES port of Wolf3d because the CPU was even slower, so I suppose that answers it! There's also a note in the GEBB page 164 from Carmack where he says it was slower than "looping through a few long wall segments". [1] Early alpha versions of DOOM used a sector-based rendering technique, maybe like what you're describing, which ultimately was too slow [2]][3]. Then Carmack switched to BSP trees after doing the Wolf3d SNES port. I think it would be pretty interesting to implement the same game with both a raycasting approach and a BSP or Build-style portal/sector approach and compare performance on a 386. DOOM ran terribly on a 386 but it did a lot more than Wolf3d, so it's not a great comparison. Catacomb 3D didn't use raycasting (it used a wall span rendering techniqe) and ran better than Wolf3d on similar hardware, but it had a bunch of glitches. But Carmack says they were due to lack of experience rather than the technique itself. Anyway thanks for challenging my assumptions. This'll go on my todo list! [0] link [1] link [2] ▶ this video [3] link