Chunks are the method used by Notch to divide "infinite" maps in the alpha and beta releases. They are 16 blocks wide, 16 blocks long, and 128 blocks deep, which is 32,768 blocks total. When wandering the world nearby chunks are generated around the player. The exact number is variable on single player depending on view distance and movement. In multiplayer, a grid with radius 10 (for a total of 21x21 or 441 chunks) is loaded around each player and sent to the player by default, although this radius can be configured. These chunks may have activity (mobs spawning, trees growing, water flowing, dropped items disappearing etc.), while the other world chunks are inactive, stored on your hard drive. If a player goes to an area that is beyond the already generated chunks, new chunks are generated and stored to the drive. As of the update on December 20, 2010, SMP servers tend to save chunks less often. Chunks will not save again if they were saved in the last 30 seconds.
Slimes can only spawn in specific chunks, determined by a calculation performed on the chunk coordinates. There are a number of utilities and mods which allow the player to tell which chunks they can spawn in; see the Slime article for details.
Creation of Chunks
Chunks are created with the help of the Map-Seed, which means that the chunks are always the same if you would use the same Seed again (on the same version at least).
Finding Chunk Edges
- Pressing the "F3" button opens the Debug screen which shows the player's X, Y, and Z coordinates. These coordinates will change as the player moves around. X and Z coordinates that are divisible by 16 represent the boundaries between chunks. EG: (96, -32) is a corner where four chunks meet. One of those chunks is between X coordinates 80 to 96 and Z coordinates -48 to -32. Another one is between X coordinates 96 to 112 and Z coordinates -32 to -16, and so on. When either X or Z crosses a multiple of 16, the player is moving across chunks.
- One can make a timer with repeaters and hook up a sticky piston to it. Put glowstone in front of the piston. The light will flicker while the piston moves and if you are up on a high pole, one can see that the light updates on the chunks at slightly different times. This can also be achieved with 2 regular pistons.