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Comment by joegibbs | Hacker News Reader

This is brilliant - I've used plenty of LUTs for post-processing but it never occurred to me to use them for recolouring assets as well.

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This reminds me, we used a command line tool (originally made for Warcraft 2?) to take full color art assets and find a palette of 200 or so colors (the rest reserved for UI elements and the player characters) for the different areas in Diablo 2, and then remapped all the art assets to these small palettes, and then reuse the monster art with other colors within these palettes for varieties of monsters. I don't remember spending more than a day on putting this in our art pipeline, the guy who wrote the tool did all the hard work.

That's really impressive!

Doom used a lookup table for random numbers: https://doom.fandom.com/wiki/Pseudorandom_number_generator

Does this mean the engine is fully deterministic?

Yes, if you make the exact same inputs you will get the exact same outcome. Demos and multiplayer rely on this, they just record player inputs, nothing about enemy movement or anything like that. This is also why you can leave a multiplayer game in the middle of a match, but you can't join one in the middle

https://www.youtube.com/watch?v=pq3x1Jy8pYM

Yes, and that speed runs can be “seed runs” where you do things to make the right LUT number come up at the right time.

The DooM Engine Black Book goes into details.

https://fabiensanglard.net/doom_fire_psx/ also

Other games use seeded random number generators to be entirely deterministic even though random; Factorio does this to allow multiplayer without having to sync the entire game state all the time.

Yeah, developer commentaries are a goldmine in general for small gold nuggets of knowledge like that. Never would have come up with such an use-case either.

Are there any other dev commentaries you recommend (other than the mentions in your post)?

Basically, all of the Valve ones. (Half-life 2, Half-life 2 Episode 1, Half-life 2 Episode 2, Team Fortress 2, Left 4 Dead, Left 4 Dead 2, Half-Life Alyx)

Each one of them is a time capsule of the techniques and game design philosophies at the time of development. Pretty sure there is a walk through on youtube for every single one of them, if you don't want to get the games yourself.

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