GoKawiilBreakdown shows NetHack's Gnomish Mines use four-pass cellular automata
A technical write-up details how NetHack generates its Gnomish Mines levels: 40% of cells are randomly set as floor, then four passes of cellular automata rules (based on counting floor neighbors) reshape the grid into organic cave layouts, with a final step adding corridors to connect any isolated caves. The author breaks down each pass's rule set, noting that the first pass is applied without buffering while the remaining three use buffered updates across the whole grid.
GoKawiil's interpretation of the reporting above, not reported fact.
The analysis illustrates how simple local rules—used in classic cellular automata like Conway's Game of Life—can generate convincing organic-feeling spaces inside a game otherwise dominated by rectangular rooms. The author flags that the purpose of the second pass's specific rule (turning floor to rock at exactly 5 neighbors) is unclear, suggesting there may be undocumented design reasoning behind NetHack's decades-old generation code worth further investigation by the roguelike community.
- NetHack's Gnomish Mines levels start as 40% randomly placed floor tiles before automata refinement.
- Four distinct cellular automata passes serve different purposes: clustering, an unexplained step, and two erosion passes.
- The first pass updates cells in place (unbuffered) while later passes update the whole grid at once (buffered).
NetHack Guidebook paperback reprint — If dungeon-generation internals like the Gnomish Mines' cellular automata fascinate you, a print NetHack guidebook makes a great companion for digging deeper into the game's mechanics and lore. It's a fun physical reference for roguelike enthusiasts who want to study the game away from a screen. Perfect for pairing with your own experiments into procedural generation.
See NetHack Guidebook paperback reprint on Amazon → Affiliate link — we may earn a commission on purchases, at no extra cost to you. Product picked by AI based on this article; it is not a tested recommendation.Source: boristhebrave.com, 2026-10-19
Published there as: “Dungeon Generation in the Gnomish Mines of NetHack”
Read the original report → The summary and analysis above are GoKawiil's own, written from reporting by the source above. Facts and quotes belong to the original publisher.