M2 files - cmangos/issues GitHub Wiki
M2 or MDX files are used to store polygon models along with their animations and other information. The file format is plain binary - no chunks. Information is mainly from http://www.pxr.dk/wowdev/wiki/index.php?title=M2 as well as from PseuWoW source.
Blizzard uses an left-handed (?) Z-up coordinate system for the models. When loading, coordinate conversions must be applied for other coordinate systems. This also must be done for all animation data.
M2 files start with a header block which contains an index of number-offset pairs for all other data blocks. All other blocks follow after that one. Blocks are not delimited, but seem to be aligned to 16 byte boundaries.
| Position | 0 |
|---|---|
| Length | 324 bytes |
The file format is identified by the magic string "MD20". Pairs of uint32 are given for every data block. nXXX describes the number of elements (not necessarily bytes) in this block while ofsXXX gives the offset to the beginning of the block. If a block does not exists, n and ofs are 0.
Offset Type Description
--------------------------------------------------------------------
0x000 char[4] Magic Bytes => "MD20"
0x004 uint32 Version (0x100 before Burning Crusade, 0x104 after BC)
0x008 uint32 nName - model name length (including \0)
0x00C uint32 ofsName - model name offset
0x010 uint32 GlobalModelFlags (0,1,3 seen)
0x014 uint32 nGlobalSequences - number of global sequences
0x018 uint32 ofsGlobalSequences - offset to global sequences
0x01C uint32 nAnimations - number of animation sequences
0x020 uint32 ofsAnimations - offset to animation sequences
0x024 uint32 nAnimationLookup
0x028 uint32 ofsAnimationLookup
0x02C uint32 nD - always 201 or 203 depending on client version
0x030 uint32 ofsD
0x034 uint32 nBones - number of bones
0x038 uint32 ofsBones - offset to bones
0x03C uint32 nSkelBoneLookup - skeletal bone lookup table
0x040 uint32 ofsSkelBoneLookup
0x044 uint32 nVertices - number of vertices
0x048 uint32 ofsVertices - offset to vertices
0x04C uint32 nViews - number of views (LOD versions?) 4 for every model
0x050 uint32 ofsViews - offset to views
0x054 uint32 nColors - number of color definitions
0x058 uint32 ofsColors - offset to color definitions
0x05C uint32 nTextures - number of textures
0x060 uint32 ofsTextures - offset to texture definitions
0x064 uint32 nTransparency - number of transparency definitions
0x068 uint32 ofsTransparency - offset to transparency definitions
0x06C uint32 nI - always 0
0x070 uint32 ofsI
0x074 uint32 nTexAnims - number of texture animations
0x078 uint32 ofsTexAnims - offset to texture animations
0x07C uint32 nTexReplace
0x080 uint32 ofsTexReplace
0x084 uint32 nRenderFlags - number of blending mode definitions
0x088 uint32 ofsRenderFlags - offset to blending mode definitions
0x08C uint32 nBoneLookupTable - bone lookup table
0x090 uint32 ofsBoneLookupTable
0x094 uint32 nTexLookup - number of texture lookup table entries
0x098 uint32 ofsTexLookup - offset to texture lookup table
0x09C uint32 nTexUnits - texture unit definitions?
0x0A0 uint32 ofsTexUnits
0x0A4 uint32 nTransLookup - number of transparency lookup table entries
0x0A8 uint32 ofsTransLookup - offset to transparency lookup table
0x0AC uint32 nTexAnimLookup - number of texture animation lookup table entries
0x0B0 uint32 ofsTexAnimLookup - offset to texture animation lookup table
0x0B4 float[14] float values ... ? (in range -1000...1000, mostly in -20...30)
0x0EC uint32 nBoundingTriangles
0x0F0 uint32 ofsBoundingTriangles
0x0F4 uint32 nBoundingVertices
0x0F8 uint32 ofsBoundingVertices
0x0FC uint32 nBoundingNormals
0x100 uint32 ofsBoundingNormals
0x104 uint32 nAttachments
0x108 uint32 ofsAttachments
0x10C uint32 nAttachLookup
0x110 uint32 ofsAttachLookup
0x114 uint32 nAttachments_2
0x118 uint32 ofsAttachments_2
0x11C uint32 nLights - number of lights
0x120 uint32 ofsLights - offset to lights
0x124 uint32 nCameras - number of cameras
0x128 uint32 ofsCameras - offset to cameras
0x12C uint32 nCameraLookup
0x130 uint32 ofsCameraLookup
0x134 uint32 nRibbonEmitters - number of ribbon emitters
0x138 uint32 ofsRibbonEmitters - offset to ribbon emitters
0x13C uint32 nParticleEmitters - number of particle emitters
0x140 uint32 ofsParticleEmitters - offset to particle emitters
| Position | header.ofsVertices |
|---|---|
| Element size | 48 bytes |
Vertices are global for all submeshes and views.
Offset Type Description
--------------------------------------------------------------------
0x00 float[3] Position (X,Y,Z)
0x0C uint8[4] Bone weights (0 to 255)
0x10 uint8[4] Bone indices (0 to nBones-1)
0x14 float[3] Normal vector (nX, nY, nZ)
0x20 float[2] Texture coordinates (U, V)
0x28 float[2] unknown, mostly 0.0f
| Position | header.ofsViews |
|---|---|
| Element size | 44 bytes |
It is not clear what Views are for. But there are always 4 of them.
Offset Type Description
--------------------------------------------------------------------
0x00 uint32 nIndex - number of elements in the index list
0x04 uint32 ofsIndex - offset to the index list
0x08 uint32 nTriangle - number of elements in the triangle list (this is 3* the number of triangles to be drawn)
0x0C uint32 ofsTriangle - offset to the triangle list
0x10 uint32 nProps - number of elements in the vertex property list
0x14 uint32 ofsProps - offset to the vertex property list
0x18 uint32 nSubmesh - number of elements in the submesh list
0x1C uint32 ofsSubmesh - offset to the submesh list
0x20 uint32 nTexture - number of elements in the texture list
0x24 uint32 ofsTexture - offset to the texture list
0x28 uint32 LOD distance or something?
nIndex uint16 values - referencing vertices from the global Vertex list.
3 uint16 values per triangle - referencing the Index list
4 bytes per Vertex. Those are indices into the BoneLookupTable for each Vertex.
32 bytes per Submesh definition.
Offset Type Description
--------------------------------------------------------------------
0x00 uint32 Mesh part ID
0x04 uint16 ofsVertex - Starting vertex number, offset into the Vertex array
0x06 uint16 nVertex - Number of vertices
0x08 uint16 ofsTriangle - Starting triangle index
0x0A uint16 nTriangle - Number of triangle indices
0x0C uint16 nBoneLookup - Number of elements in the bone lookup table
0x0E uint16 ofsBoneLookup - Starting index in the bone lookup table
0x10 uint16 unknown
0x12 uint16 unsure - maybe root bone?
0x14 float[3] Vector (3d) - mass center?
Mesh part ID
These IDs are referenced for Geosets and such. For character models, each hairstyle/thick armor/etc is present in the mesh, so to render a character with a specific set of looks, some of the submeshes should be omitted based on this ID.The submeshes are sorted into groups. Groups are like this for character models. They can be different for other models.
00**: Hairstyles
01**: Facial1
02**: Facial2
03**: Facial3
04**: Braces
05**: Boots
06**: Unknown
07**: Ears
08**: Wristbands
09**: Kneepads?
10**:
11**: Related to pants
12**: Tabard
13**: Trousers / kilts
14**:
15**: Cape
16**:
17**: Eyeglows (including the deathknight ones)
18**: Belt / bellypack
These are referenced in CreatureDisplayInfo.dbc->creatureGeosetData.