Pocket Minecraft Map Format

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This article describes the Chunk format used in the Full Chunk Data (0xbf, clientbound).

Concepts

  • Chunk: a 16×128×16 area, sometimes also called chunk section

Format

A chunk consists of the following fields (fixed size of 83200 bytes):

Field Name Field Type Notes
Blocks Array of bytes Always a size of 32,768 bytes
Regular Data Array of bytes Always a size of 16,384 bytes
Sky Light Array of bytes Always a size of 16,384 bytes, half byte per block
Block Light Array of bytes Always a size of 16,384 bytes, half byte per block
Height Map Array of ints Always a size of 256 bytes
Biome Colors Array of ints Always a size of 1024 bytes

Blocks

The following definitions are provided to clarify the mapping between the location of a block within a LevelDB entry containing a chunk of 32,768 blocks and the corresponding location of the block within the entire world:

  • Let X and Z be the values contained within the LevelDB key.
  • Let C[] be a three dimensional array of the chunk of 32,768 blocks contained within the LevelDB entry. The first two indices i and j range from 0 to 15, and the third index y ranges from 0 to 127.
  • Let W[] be a three dimensional array of the blocks contained within the entire world.

For infinite worlds, the first two indices x and z both range over the values of a four byte integer and may be negative as well as positive.

The third index y ranges from 0 to 127 for both old style and infinite worlds.

Assuming the definitions above, the location of a block with a LevelDB entry with key values X and Z maps to the corresponding location of the block within the entire world as follows: 

let x = 16 * X + i
let z = 16 * Z + j
C[i, j, y] <-> W[x, z, y]

Skylight/Blocklight/Metadata

Block light and skylight are very similar to the 1.8 implementation used in the Minecraft: PC edition of the game. All chunks always have the same value and have a fixed size of 83200, you can index the skylight/blocklight/metadata by block by using (x * 2048) + (z * 128) + y where x, y, z are the coordinates of the block you are trying to retrieve the skylight/blocklight/metadata for.

Heightmap

The heightmap is the mapping between the height of each block in a chunk for retrieveing by x and z you can simply (z << 4) + x to get the value or set it.

Biome colors

Each block in a single column has a biome id and (unlike the PC version of the game) an r, g, b value associated with it that is used for the client to render the color (more like hue) of the block. For finding/setting the biome id for a column of blocks the key for each column is (z << 4) + x and the integer that you pack inside the value is (current & 0xFFFFFF) | (biomeId << 24) where current = biomes[(z << 4) + x] and biomeId = the id of the biome for getting the id, it is the same but you just reverse it (current & 0xFF000000) >> 24 where current = biomes[(z << 4) + x]. For setting the r, g, b color of each chunk you can do a similar key [(z << 4) | x] and unpack the r, g, b by color >> 16, (color >> 8) & 0xFF, color & 0xFF and pack it again by getting the correct color (biome[(z << 4) + x] & 0xFF000000) | ((R & 0xFF) << 16) | ((G & 0xFF) << 8) | (B & 0XFF).

LevelDB

In the Minecraft: PE application, all chunks are stored in Mojang’s fork of LevelDB (a ZLib compressed LevelDB database) each key follows the same format unless you are using a special key, or a nether key

For an overworld key, it is quite trivial (always 9 bytes long):

Field Name Field Type
X Coordinate Little-endian int
Z Coordinate Little-endian int
Type A byte containing the type of data, see bytes below

For a nether key it is similar, but with an extra byte after Z Coordinate (always 13 bytes long):

Field Name Field Type
X Coordinate Little-endian int
Z Coordinate Little-endian int
Nether specifier Little-endian int, always a value of 1
Type A byte containing the type of data, see bytes below

The corresponding byte specifier for the type of chunk are:

Field Name Field Value
Terrain Data 0x30 (48 in decimal, ‘0’ ASCII)
Tile Entity Data 0x31 (49 in decimal, ‘1’ ASCII)
Entity Data 0x32 (50 in decimal, ‘2’ ASCII)
1-byte Data 0x76 (118 in decimal, ‘v’ ASCII)

Tile Entity Data and Entity Data are encoded as NBT, the format of Terrain Data is specified above.

Implementations

Sources

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