World Features

There are two or three interrelated categories which provide various features to a world. Some do simple modifications of the terrain, others add complex structures.

Up to V11, these were divided into two categories, based on their implementation within the game: "Populators" and "Terrain Alterations". The difference between "terrain alterations" and "populators" is based ultimately on how they work in the code. In general, "populators" run late in chunk generation and add things, while "terrain alterations" run early in chunk generation (approximately right after biome top replacement) and generally remove stone. Ore placement, for example, runs in the populator stage. In code, the distinction is that a "terrain alteration" must be deterministic for a seed and chunk, and must be able to generate a large feature (such as a cave system) section by section without having to "draw" what it is doing into other chunks (such as how a village plops down buildings across multiple chunks).

In V12, these groups were merged and redivided into "Small Features", "Medium Features", and "Large Features". These categories are based on how prominent they are in the world; for example, large but scarce structures are in Medium rather than Large. There are explicit "dummy" entries for each category, but "No Small Features" and "No Medium Features" produce instability (presumably from overcontrolling the world).

Populators
Crystalline Formations Deep Lakes Dense Ores Dungeons Huge Trees Mineshafts Nether Fortress Obelisks Spikes Star Fissure Strongholds Surface Lakes Villages

Terrain Alterations
Caves Floating Islands Ravines Skylands Spheres Tendrils

Small Features
Crystalline Formations Deep Lakes Lacking Small Features Obelisks Star Fissure Surface Lakes

Medium Features
Dungeons Lacking Medium Features Mineshaft Nether Fortress Ravines Spheres Spikes Strongholds Villages

Large Features
Caves Dense Ores Floating Islands Huge Trees Lacking Large Features Skylands Tendrils