rswiki-book/src/317/317-Construct-map-region.md

Construct Map Region

The construct map region packet sends a dynamic map region that is constructed by using groups of 8x8 tiles. It is generally used for instanced areas, such as fight caves, and in later revisions, player owned houses.

Packet Details

Key	Value
Name	Construct map region
Description	Constructs a new map region from a palette of 8x8 tiles.
Opcode	241
Type	Variable Short
Length	N/A
Revision	317

Packet Structure

Data Type	Description
Short Special A	The region Y coordinate (absolute Y coordinate / 8), plus 6.
Bit block	See below.
Short	The region X coordinate (absolute X coordinate / 8), plus 6.

Bit block

The bit block contains the 'palette' of map regions to make up the new region.

A loop is used to construct it, as follows:

for (int z = 0; z < 4; z++) {
    for(int x = 0; x < 13; x++) {
        for(int y = 0; y < 13; y++) {
            // data for this region
        }
    }
}

The individual format in each iteration of the loop is:

• 1 bit - set to 0 to indicate to display nothing, 1 to display a region
• 26 bits - if the flag above is set to 1: region_x << 14 | region_y << 3