Water.extm

Generated water material map of Hyrule Main Field

water.extm files describe the water heightmap and the texture of the main field and add-on content field.

water.extm File Specification

water.extm File Layout

Each file contains a 64×64 grid. For each vertex there is 8 bytes of data that describe the height of the mesh, the material type and flow speed.

Water Map Data

Each entry in the water data table is 8 bytes long.

Offset (h)	Size	Data Type	Description
0x00	2	Unsigned Short	height (Vertex y component)
0x02	2	Unsigned Short	xAxisFlowRate 128 = no flow
0x04	2	Unsigned Short	zAxisFlowRate 128 = no flow
0x05	1	Unsigned Byte	materialIndex + 3. This may act as a checksum?
0x06	1	Unsigned Byte	materialIndex

height and flowSpeed are stored as unsigned shorts, but seem to map to float values. These can be calculated by dividing by the max size of an unsigned short:

32767 / 0xffff = 0.5

height is further multiplied by another constant to get the final height (the constant is unknown at this time, but is close to 0x300 / 0xffff).

x and z can be calculated, while iterating through the data table:

for (int index = 0; index < 64 * 64; index++) {
    uint x = index % 64;
    uint z = index / 64;
}

Flow Rates are calculated as (flowRate * 2) - 1 and ranges from -1 to 1. On the x-axis this changes flow direction from East (-1) to West (+1) and on the z-axis from North (-1) to South (+1).

Material Index

This data is stored in Terrain.Tex1.bfres.

id	file	name	attribute	attribute_sub	flag	Google Translated
0	Water	水	Water	Water	0	Water
1	HotWater	熱湯	Water	Water_Hot	0	Hot water
2	Poison	毒水	Water	Water_Poison	0	Poison water
3	Lava	溶岩	Lava	Lava	0	Lava
4	IceWater	冷たい水	Water	Water_Ice	0	Cold water
5	Mud	泥沼	Bog	Bog	0	Bog
6	Clear01	透明水01	Water	Water	0	Clear water 01
7	Sea	海	Water	Water	0	Ocean