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water.extm File Specification

water.extm files describe the water heightmap and the texture of the main field and add-on content field.
File Locations vol/content/Terrain/A/MainField/
Extension .water.extm
Parent Archive .water.extm.sstera
Endianness Little Endian

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.

struct waterData {
    unsigned short height;
    unsigned short xAxisFlowRate;
    unsigned short zAxisFlowRate;
    unsigned char unk00;
    unsigned char materialIndex;
};
Offset Length Type Description
0x00 2 Unsigned Short height (Vertex y component
0x02 2 Unsigned Short xAxisFlowRate.
0x04 2 Unsigned Short zAxisFlowRate.
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 furthur multiplied by another constant to get the final height (the constant is unknown at this time).

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;
}

Note that z is expected to be an integer quotient. The floor function can be used if integer division is not supported.

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

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

This data is stored in Terrain.Tex1.bfres