Warcraft III Map Format (W3M / W3X)

Warcraft III maps are stored as MPQ archives with a .w3m (melee/campaign) or .w3x (custom scenario) extension. Inside each archive a set of binary and text files describes the map's terrain, units, triggers, strings, and metadata.

Archive Layout

Map archives are MPQ v1 (often with HM3W user data before the MPQ\x1a header). Sector size is 512 << wSectorSizeShift. Ordinary World Editor maps use shift 3 (4 KiB). Some protected custom maps raise shift to Storm's maximum of 15 (16 MiB), so the reader must not clamp large sector sizes down to 4 KiB.

A typical map archive contains the following files:

File	Description
war3map.w3i	Map info (name, author, players, camera bounds)
war3map.w3e	Terrain environment (tile types, heights, cliff levels)
war3map.doo	Doodad placement
war3map.w3u	Unit object data overrides
war3map.w3t	Item object data overrides
war3map.w3b	Destructible object data overrides
war3map.w3d	Doodad object data overrides
war3map.w3a	Ability object data overrides
war3map.w3q	Upgrade object data overrides
war3map.shd	Shadow map
war3map.wpm	Pathing map
war3map.j	JASS script (map triggers)
war3map.lua	Lua script (maps saved in v1.31+)
(listfile)	Archive file list

Map Info File (war3map.w3i)

This is the first file read at world load time (CM_ReadInfo in common/world.c). It is a flat binary record with the following layout:

DWORD  fileFormat          // map format version
DWORD  numberOfSaves       // incremented by the World Editor each save
DWORD  editorVersion       // World Editor build number
CSTR   mapName             // null-terminated display name
CSTR   mapAuthor
CSTR   mapDescription
CSTR   playersRecommended
...
FLOAT[8]  cameraBounds     // initial four camera-bound corner points; copied into per-player runtime camera bounds
LONG[4]   cameraComplements // W3I complements in left, right, bottom, top order (tiles)
SIZE2     playableArea     // width × height in tiles
DWORD     flags
CHAR      mainGroundType   // e.g. 'A' = Ashenvale, 'L' = Lordaeron
...
DWORD  num_players
[playerRecord × num_players]
DWORD  num_forces
[forceRecord × num_forces]
...

For W3I format 25 and later, the loading/prologue block includes gameDataSet. OpenRealm interprets it using the same branch as Warsmash: 1 means the Custom_V<edition> data overlay, while other explicit values mean Melee_V<edition>. Zero (and RoC W3I files where the field does not exist) falls back to the melee_map flag: melee maps select Melee and other maps select Custom. The <edition> suffix comes from fs_expansion (0 RoC, 1 TFT), not from the W3I format version. See WC3 Data Model.

W3I format version remains a separate runtime compatibility signal. G_IsReignOfChaosMap() treats parsed versions 1..24 as RoC; format 25 and later is not RoC. This is used for behavior differences, not for choosing the Custom versus Melee overlay.

The four W3I camera-bound complements are stored in left, right, bottom, top order. They describe how many terrain cells on each side of the complete W3E terrain lie outside the playable rectangle; they are not the JASS GetCameraMargin values. OpenRealm stores them as cameraBounds.complement in the same on-disk order because the W3I reader copies the structure directly. The playable rectangle is reconstructed from CM_GetWorldBounds() as:

playable.min.x = world.min.x + complement.left   * 128
playable.max.x = world.max.x - complement.right  * 128
playable.min.y = world.min.y + complement.bottom * 128
playable.max.y = world.max.y - complement.top    * 128

The eight W3I camera-bound floats form the default camera rectangle. Warcraft's GetCameraMargin is the inset between that default camera rectangle and the playable rectangle:

LEFT   = default.min.x - playable.min.x
RIGHT  = playable.max.x - default.max.x
BOTTOM = default.min.y - playable.min.y
TOP    = playable.max.y - default.max.y

This matches Warsmash's Terrain.getPlayableMapArea()/getDefaultCameraBounds() mapping and its JASS GetCameraMargin native (Terrain.java and Jass2.java in WarsmashModEngine). World Editor generated main functions add/subtract these margins from playable-map edge constants when calling SetCameraBounds, thereby reconstructing the default camera rectangle. Returning complement * TILE_SIZE from GetCameraMargin applies the unplayable border a second time and makes the runtime camera stop substantially too early at map edges.

Each playerRecord contains: - player slot index - player type (human / computer / neutral / rescuable) - player race (human / orc / undead / night elf) - flags (fixed start position, etc.) - player name (null-terminated string) - starting position (X, Y floats) - ally priority flags

Terrain File (war3map.w3e)

The terrain file encodes a grid of vertices. Each vertex stores:

Field	Type	Description
height	SHORT	Ground height (scaled by 4)
waterHeight	SHORT	Water surface height
flags	BYTE	Ramp / boundary / water presence bits
groundTextures[4]	BYTE[4]	Indices into the tileset texture table
cliffTexture	BYTE	Cliff face texture index
layerHeight	BYTE	Cliff level (0 = sea floor, 1 = base, 2 = raised, …)

The Warcraft III renderer (games/warcraft-3/renderer/w3m/) reads each vertex and constructs mesh layers:

• Ground layer — a quad grid textured with the four ground texture slots, blended by the per-vertex weights.
• Cliff layer — vertical faces extruded between adjacent vertices at different cliff levels.
• Water layer — a translucent quad grid rendered wherever the water-presence bit is set.

Height Calculation

// games/warcraft-3/renderer/w3m/r_war3map_utils.c
float GetWar3MapVertexHeight(LPCWAR3MAPVERTEX vert) {
    return (vert->height - 0x2000) / 4.0f;
}
float GetWar3MapVertexWaterLevel(LPCWAR3MAPVERTEX vert) {
    return (vert->waterHeight - 0x2000) / 4.0f;
}

The raw SHORT is biased by 0x2000 (8192) to allow negative heights, then divided by 4 to give world-space units.

Doodad File (war3map.doo)

Doodads are decorative or destructible objects placed in the editor. Each record encodes:

• object type ID (4-byte tag, e.g. 'ATtr')
• variation index
• world-space X, Y, Z position
• rotation angle (radians)
• scale X, Y, Z
• skin override flags and life percentage

Pathing Map (war3map.wpm)

A 2-bit-per-cell grid at 1/4 tile resolution. Each cell encodes walkability, flyability, buildability, and blight status. The Warcraft III pathfinder (games/warcraft-3/game/g_pathing.c) reads this map to determine which cells units can traverse.

Object Data Overrides

Files such as war3map.w3u (units) override individual fields of the base SLK tables. The format is:

DWORD  version
DWORD  num_original_records
[original record × num_original_records]
DWORD  num_custom_records
[custom record × num_custom_records]

Each record contains a four-character unit ID followed by a list of (field_tag, value) pairs, terminated by a zero DWORD.

OpenRealm currently applies registered UnitBalance_t, UnitProfile_t, and UnitUI_t fields at map load. Stable per-map rows preserve balance fields such as usma/usrg/usst, custom uani Required Animation Names, umdl model paths, and the other mapped Balance/Profile/UI fields when a custom rawcode otherwise resolves to its base SLK unit. Original-unit edits are applied before custom-unit inheritance. Data/Weapons/Abilities are still base-row fallbacks and must not be assumed to honor all war3map.w3u fields yet. See docs/wc3-data-model.md and docs/games/warcraft-3/unit-animation-properties.md.

Related Source Files

Source	Purpose
common/world.c	Map archive loading and info parsing
games/warcraft-3/renderer/w3m/r_war3map.c	Terrain mesh construction
games/warcraft-3/renderer/w3m/r_war3map_ground.c	Ground layer geometry
games/warcraft-3/renderer/w3m/r_war3map_cliffs.c	Cliff geometry
games/warcraft-3/renderer/w3m/r_war3map_water.c	Water layer geometry
games/warcraft-3/game/g_pathing.c	Pathfinding using the pathing map