Prebuilt worlds are the hand built Kingdom Keys worlds (eg. Destiny Islands, Daybreak Town). They have two parts:

• The world's blocks, in the kk_worlds/<world name>/ folder. These are NBT files, not JSON, and aren't written by hand: they're produced in game with the /kingdomkeys export command (see [[#Exporting a world]]).
• A dimension JSON in the dimension folder that uses the kingdomkeys:prebuilt_world_generator generator to rebuild those blocks chunk by chunk.

The dimension and dimension_type files are vanilla Minecraft data pack files (see dimension and dimension type on the Minecraft wiki), only the generator is specific to Kingdom Keys. To make a new world reachable with the Gummi Ship it also needs a Gummi World file.

Prebuilt world generator

Set as the generator of a dimension JSON, here is its structure:

• (string) type: must be "kingdomkeys:prebuilt_world_generator".
• (string) world: the id of the kk_worlds folder to build from, eg. kingdomkeys:destiny_islands reads data/kingdomkeys/kk_worlds/destiny_islands/.
• [optional] (array of 3 integers) origin: the [x, y, z] position where the lowest corner of the export is placed. X and Z should be multiples of 16 so the pieces line up with chunks. Default [0, 0, 0].
• (object) biome_source: a vanilla biome source, eg. { "type": "minecraft:fixed", "biome": "minecraft:warm_ocean" }. Biome features (ores, plants...) are not generated, only the exported blocks.
• [optional] (object) sea: a sea poured around the build so the world sits in an ocean. If not set, everything outside the build is void.
  • [optional] (string) water: the block the sea is made of. Default minecraft:water.
  • (integer) level: the Y of the water surface (exclusive, like vanilla's sea level).
  • (integer) floor: the average Y of the top of the sea bed. Match it to the sea bed of the export so there is no visible seam.
  • [optional] (integer) variation: how many blocks below floor the sea bed is allowed to dip. Default 3.
  • [optional] (integer) surface_depth: how many blocks of surface are placed on top of body. Default 4.
  • [optional] (string) body: the block for the bulk of the sea bed. Default minecraft:stone.
  • [optional] (string) surface: the block covering the sea bed. Default minecraft:sand.
  • [optional] (string) patches: a block scattered through the surface for variety, eg. gravel or clay. If not set there are no patches.
  • [optional] (string) bedrock: the block placed at the very bottom of the world. If not set the bottom is left open.

{
  "type": "kingdomkeys:daybreak_town",
  "generator": {
    "type": "kingdomkeys:prebuilt_world_generator",
    "world": "kingdomkeys:daybreak_town",
    "origin": [0, 64, 0],
    "sea": {
      "water": "minecraft:water",
      "level": 66,
      "floor": 64,
      "variation": 2,
      "surface_depth": 4,
      "body": "minecraft:stone",
      "surface": "minecraft:sand",
      "bedrock": "minecraft:bedrock"
    },
    "biome_source": { "type": "minecraft:fixed", "biome": "minecraft:warm_ocean" }
  }
}

Exporting a world

Build the world in any dimension (creative works best), then run as an operator:

/kingdomkeys export <name> <from> <to> [entities]

• name: the folder name the export is saved as.
• from / to: two opposite corners of the area to export. The area is extended to whole chunks horizontally.
• [optional] entities: whether to also save entities like paintings, item frames and armor stands. Default true.

The files are written to <game folder>/kingdomkeys/exports/<name>/: a manifest.nbt plus one <x>_<z>.nbt piece per chunk (empty chunks get no file). Running the command again with the same name merges into the existing export, so a big world can be exported in several parts. Copy the whole folder to data/<namespace>/kk_worlds/<name>/ in your data pack and point a dimension's world field at it.