"A cave is a natural opening large enough to admit a human explorer and which some explorers, at least, choose to call a cave"
-Caving Basics, NSS
In nature, caves are formed by chemical processes (Dissolution caves, lava caves, ice caves) or mechanical processes (Tectonic caves, Eolian caves etc).
In code a cave is formed to yield organic-looking passages and chambers.
PCG Wiki References
- Most methods of Dungeon generation can be coaxed to generate natural looking caves.
Cave like levels on Roguebasin, using Cellular Automata.
Island and labyrinth map generating algorithm generates natural looking passages.
Irregular Shaped Rooms on RogueBasin
Procedural Generation 1 article on Cave Generation in Game Maker.
There is a thread on rec.games.roguelike.development on cavern-type dungeons.
Procedural Generation - The Caves - Blog post on cave generation.
Cave - Wikipedia article on Caves.