WDL/v18

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WDL files contain a low-resolution heightmap for a world. This is probably what the WoW client uses to draw the solid-colored mountain ranges in the background ('in front of' the sky, but 'behind' the fog and the rest of the scenery). It can also be conveniently used to construct a minimap - however, since no water level information is present, the best guess is 0 (sea level) - this results in some lower-than-sea-level areas being blue on the WoWmapview minimap. Oh well. :)

MWMO, MWID and MODF chunks

These chunks seem to have been added to every WDL and contain information about low resolution WMO used to create a silhouette.

MWMO

  • Filenames for WMO that appear in the low resolution map. Zero terminated strings.

MWID

  • List of indexes into the MWMO chunk.

MODF

  • Placement information for the WMO. Appears to be the same 64 byte structure used in the WDT and ADT MODF chunks.

MAOF chunk

  • Map Area Offset.

Contains 64*64 = 4096 unsigned 32-bit integers, these are absolute offsets in the file to each map tile's MapAreaLow-array-entry. For unused tiles the value is 0.

/*000h*/ UINT32 areaLowOffsets[4096];
or
/*000h*/ UINT32 areaLowOffsets[64][64];

MapAreaLow array

WoD (cata?): if neither MAHO nor MARE present: CMapAreaLow::CreateOceanInstance()

MARE chunks

  • Map Area

Heightmap for one map tile. Contains 17*17 + 16*16 = 545 signed 16-bit integers. So a 17 by 17 grid of height values is given, with additional height values in between grid points. Here, the "outer" 17x17 points are listed (in the usual row major order), followed by 16x16 "inner" points. The height values are on the same scale as those used in the regular height maps.

MAOC chunk (<Legion)

This section only applies to versions ≤ WoD.
// optional
struct MAOC
{
  short[];
}

MAOE chunk (Legion+)

This section only applies to versions ≥ Legion.
// optional, but shall be before MAHO else ignored
// This defines ocean (float?) texture (m_ocean or AreaOceanAlphaTexture)
struct
{
  // ??? fixed size 0x20, some mask?
};

MAHO chunks

After each MARE chunk there follows a MAHO (MapAreaHOles) chunk.

This chunk is an array of 16 uint16_t values. Each one is a bitmask, representing a boolean value that determines whether or not there is a hole at that position - if the bit is not set, there is a hole at that position.

If the MAHO chunk is missing, the client will treat that map area as having a MAHO chunk with all values set to 0. In Blizzard's files, the chunk is always included no matter what the values are. This behavior is most likely a form of backwards compatibility to allow the client to load WDL files from before Wrath of the Lich King.