Chunk
| Packet ID | Direction | Mojang Name | MCP Name |
|---|---|---|---|
0x33 | Clientbound | BlockRegionUpdatePacket | Packet51MapChunk |
The packets is sent from the server to the client to update the blocks in the specified area.
The origin coordinate (x,y,z) is in block space. The to-be-updated volume is defined by the width, height and length bytes which the server subtracts 1 from to allow updating of a 256x128x256 area*.
* untested, but height values more than 127 seem to crash the client
The chunk size can only be positive, so the origin coordinate must always indicate the lowest value of the changed area, towards Negative X/Y/Z.
Chunk Data
How the chunk data is formatted over the network is explained on the chunk page. This data is zlib compressed when sent over the network. For more info, check out the compression page.
Clientbound
| Field | Type | Description |
|---|---|---|
| X | Integer | The X position of the chunk towards Negative X |
| Y | Short | The Y position of the chunk towards Negative Y |
| Z | Integer | The Z position of the chunk towards Negative Z |
| width | Byte | The width of the updated area towards Positive X, -1 |
| height | Byte | The height of the updated area towards Positive Y, -1 |
| length | Byte | The length of the updated area towards Positive Z, -1 |
| compressed size | Integer | The size, in bytes, of the zlib compressed data |
| compressed data | Byte Array | The zlib compressed chunk data |
WARNING
If a chunk that's taller than 127 blocks is sent, a vanilla client will softlock/crash.
Example Packet
| Field | Value |
|---|---|
| x | 0 |
| y | 0 |
| z | 0 |
| width | 15 |
| height | 127 |
| length | 15 |
| compressed size | 256 |
| compressed data | 120,218,237,205,161,13,0,32,16,4,65,2,226,37,253,119,73,7,208,1,136,51,136,25,191,217,26,153,222,50,229,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,239,255,193,31,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,120,219,119,75,175,215,235,245,122,189,94,175,215,235,245,122,189,94,175,215,235,245,122,189,94,175,215,235,245,122,189,94,175,215,235,245,122,189,94,175,215,235,245,122,189,94,175,215,235,245,122,189,94,175,215,235,245,122,125,220,207,3,138,218,152,0 |