WMO

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WMO files contain world map objects. They, too, have a chunked structure just like the WDT files.

There are two types of WMO files, actually:

The root file and the groups are stored with the following filenames:

  • World\wmo\path\WMOName.wmo
  • World\wmo\path\WMOName_NNN.wmo

WMO root file

The root file lists the following:

  • textures (BLP File references)
  • materials
  • models (MDX / M2 File references)
  • groups
  • visibility information
  • more data

MOHD chunk

  • Header for the map object. 64 bytes.
Offset 	Type 		Description
0x00 	uint32 		nMaterials - number of materials
0x04 	uint32 		nGroups - number of WMO groups
0x08 	uint32 		nPortals - number of portals
0x0C 	uint32 		nLights - number of lights
0x10 	uint32 		nModels - number of M2 models imported
0x14 	uint32 		nDoodads - number of dedicated files (*see below this table!) 
0x18 	uint32 		nSets - number of doodad sets
0x1C 	uint32 		ambient color?
0x20 	uint32 		WMO ID (column 2 in WMOAreaTable.dbc)
0x24 	float[3] 	Bounding box corner 1
0x30 	float[3] 	Bounding box corner 2
0x3C 	uint32 		LiquidType related, see below in the MLIQ chunk.
  • (*M2 instances + all groupfiles belonging to this wmo including groupfiles of dedicated rootfiles(ie StormwindHarbor.wmo to Stormwind.wmo))
struct SMOHeader // 03-29-2005 By ObscuR
{
/*000h*/  UINT32 nTextures;		
/*004h*/  UINT32 nGroups;		
/*008h*/  UINT32 nPortals;		
/*00Ch*/  UINT32 nLights;		
/*010h*/  UINT32 nDoodadNames;		
/*014h*/  UINT32 nDoodadDefs;		
/*018h*/  UINT32 nDoodadSets;		
/*01Ch*/  float ambColor[6];		
/*020h*/ 
/*024h*/  	
/*028h*/  		
/*02Ch*/ 	
/*030h*/  float pos[2];		
/*034h*/  		
/*038h*/  		
/*03Ch*/   UINT32 wmoID;		
/*040h*/ 
};

struct MOHD // --Schlumpf 20:53, 30 July 2007 (CEST)
{
/*000h*/  UINT32 nTextures;		
/*004h*/  UINT32 nGroups;		
/*008h*/  UINT32 nPortals;		
/*00Ch*/  UINT32 nLights;		
/*010h*/  UINT32 nModels;		
/*014h*/  UINT32 nDoodads;		
/*018h*/  UINT32 nSets;		
/*01Ch*/  UINT8  colR;		
/*01Dh*/  UINT8  colG;	
/*01Eh*/  UINT8  colB;		
/*01Fh*/  UINT8  colX;			
/*020h*/  UINT32 wmoID;
/*024h*/  float  bb1[3];
/*030h*/  float  bb2[3];		
/*03Ch*/  UINT32 nullish;	
};

MOTX chunk

  • List of textures (BLP Files) used in this map object. There are nTextures entries in this chunk.

A block of zero-padded, zero-terminated strings, that are complete filenames with paths. There will be further material information for each texture in the next chunk. The gaps between the filenames are padded with extra zeroes, but the material chunk does have some positional information for these strings.

The beginning of a string is always aligned to a 4Byte Adress. (0, 4, 8, C). The end of the string is Zero terminated and filled with zeros until the next aligment. Sometimes there also empty aligtments for no (it seems like no) real reason.

MOMT chunk

  • Materials used in this map object, 64 bytes per texture (BLP file), nMaterials entries.
struct SMOMaterial // based on: 03-29-2005 By ObscuR // --schlumpf_ 18:36, 5 August 2009 (CEST)
{
/*000h*/  UINT32 flags1;		
/*004h*/  UINT32 flags2;		
/*008h*/  UINT32 blendMode;		// Blending: 0 for opaque, 1 for transparent
/*00Ch*/  UINT32 texture_1;		// Start position for the first texture filename in the MOTX data block	
/*010h*/  UINT32 color_1; 
/*014h*/  UINT32 flags_1;
/*018h*/  UINT32 texture_2;		// Start position for the second texture filename in the MOTX data block	
/*01Ch*/  UINT32 color_2; 	
/*020h*/  UINT32 flags_2;
/*024h*/  UINT32 color_3; 	
/*028h*/  UINT32 unk[4];
/*02Ch*/  				//float diffColor[3] 		
/*030h*/   		
/*034h*/  		
/*038h*/  Texture* texture1;		// this is the first texture object. of course only in RAM. leave this alone. :D
/*03Ch*/  Texture* texture2;		// this is the second texture object.
/*040h*/ 		
}

The flags might used to tweak alpha testing values, I'm not sure about it, but some grates and flags in IF seem to require an alpha testing threshold of 0, at other places this is greater than 0. 

flag2 		Meaning
0x01 		?(I'm not sure atm I tend to use lightmap or something like this)
0x04 		Two-sided (disable backface culling)
0x10 		Bright at night (unshaded) (used on windows and lamps in Stormwind, for example) -ProFeT: i think that is Unshaded becase external face of windows are flagged like this.
0x20 		?
0x28 		Darkned ?, the intern face of windows are flagged 0x28
0x40 		looks like GL_CLAMP
0x80 		looks like GL_REPEAT

MOGN chunk

  • List of group names for the groups in this map object. There are nGroups entries in this chunk.

A contiguous block of zero-terminated strings. The names are purely informational, they aren't used elsewhere (to my knowledge)

i think think that his realy is zero terminated and just a name list .. but so far im not sure _what_ else it could be - tharo

MOGI chunk

  • Group information for WMO groups, 32 bytes per group, nGroups entries.
Offset 	Type 		Description
0x00 	uint32 		Flags
0x04 	3 * float 	Bounding box corner 1
0x10 	3 * float 	Bounding box corner 2
0x1C 	int32 		name in MOGN chunk (or -1 for no name?)

struct WMOGroup // --Schlumpf 21:06, 30 July 2007 (CEST)
{
/*000h*/  UINT32 flags;  		
/*004h*/  float  bb1[3];  		
/*010h*/  float  bb2[3];		
/*01Ch*/  UINT32 nameoffset;
}

Groups don't have placement or orientation information, because the coordinates for the vertices in the additional .WMO files are already correctly transformed relative to (0,0,0) which is the entire WMO's base position in model space.

The name offsets seem to be incorrect (or something else entirely?). The correct name offsets are in the WMO group file headers. (along with more descriptive names for some groups)

  • It is just the index. You have to find the offsets by yourself. --Schlumpf 10:17, 31 July 2007 (CEST)

The flags for the groups seem to specify whether it is indoors/outdoors, probably to choose what kind of lighting to use. Not fully understood. "Indoors" and "Outdoors" are flags used to tell the client whether certain spells can be cast and abilities used. (Example: Entangling Roots cannot be used indoors). 

Flag		Meaning
0x8 		Outdoor (use global lights?)
0x40		?
0x80 		?
0x2000		Indoor (use local lights?)
0x8000		Unknown, but frequently used
0x10000 	Used in Stormwind?
0x40000		Show skybox if the player is "inside" the group

MOSB chunk

  • Skybox. Always 00 00 00 00. Skyboxes are now defined in DBCs (Light.dbc etc.). Contained a M2 filename that was used as skybox.

MOPV chunk

  • Portal vertices, 4 * 3 * float per portal, nPortals entries.

Portals are (always?) rectangles that specify where doors or entrances are in a WMO. They could be used for visibility, but I currently have no idea what relations they have to each other or how they work.

Since when "playing" WoW, you're confined to the ground, checking for passing through these portals would be enough to toggle visibility for indoors or outdoors areas, however, when randomly flying around, this is not necessarily the case.

So.... What happens when you're flying around on a gryphon, and you fly into that arch-shaped portal into Ironforge? How is that portal calculated? It's all cool as long as you're inside "legal" areas, I suppose.

It's fun, you can actually map out the topology of the WMO using this and the MOPR chunk. This could be used to speed up the rendering once/if I figure out how.

MOPT chunk

  • Portal information. 20 bytes per portal, nPortals entries.
Offset	Type 		Description
0x00 	uint16 		Base vertex index?
0x02 	uint16 		Number of vertices (?), always 4 (?)
0x04 	3*float 	a normal vector maybe? haven't checked.
0x10 	float 		unknown  - if this is NAN, the three floats will be (0,0,1)

MOPR chunk

  • Portal <> group relationship? 2*nPortals entries of 8 bytes.

I think this might specify the two WMO groups that a portal connects. 

Offset 	Type 		Description
0x0 	uint16 		Portal index
0x2 	uint16 		WMO group index
0x4 	int16 		1 or -1
0x6 	uint16 		always 0

struct SMOPortalRef // 04-29-2005 By ObscuR
{
  /*000h*/  UINT16 portalIndex;
  /*000h*/  UINT16 groupIndex;
  /*004h*/  UINT16 side;
  /*006h*/  UINT16 filler;
  /*008h*/
};

MOVV chunk

  • Visible block vertices

Just a list of vertices that corresponds to the visible block list.

MOVB chunk

  • Visible block list
unsigned short firstVertex;
unsigned short count;

MOLT chunk

  • Lighting information. 48 bytes per light, nLights entries
Offset 	Type 		Description
0x00 	4 * uint8 	Flags or something? Mostly (0,1,1,1)
0x04 	4 * uint8 	Color (B,G,R,A)
0x08 	3 * float 	Position (X,Z,-Y)
0x14 	7 * float 	Unknown (light properties?)

enum LightType 
{
	OMNI_LGT,
	SPOT_LGT,
	DIRECT_LGT,
	AMBIENT_LGT
};

struct SMOLight // 04-29-2005 By ObscuR
{
  /*000h*/  UINT8 LightType; 	
  /*001h*/  UINT8 type;
  /*002h*/  UINT8 useAtten;
  /*003h*/  UINT8 pad;
  /*004h*/  UINT8 color[4];  
  /*008h*/  float position[3];
  /*014h*/  float intensity;
  /*018h*/  float attenStart;
  /*01Ch*/  float attenEnd;
  /*020h*/  float unk1;
  /*024h*/  float unk2;
  /*028h*/  float unk3;
  /*02Ch*/  float unk4;
  /*030h*/  
};

I haven't quite figured out how WoW actually does lighting, as it seems much smoother than the regular vertex lighting in my screenshots. The light paramters might be range or attenuation information, or something else entirely. Some WMO groups reference a lot of lights at once.

The WoW client (at least on my system) uses only one light, which is always directional. Attenuation is always (0, 0.7, 0.03). So I suppose for models/doodads (both are M2 files anyway) it selects an appropriate light to turn on. Global light is handled similarly. Some WMO textures (BLP files) have specular maps in the alpha channel, the pixel shader renderpath uses these. Still don't know how to determine direction/color for either the outdoor light or WMO local lights... :)

MODS chunk

  • This chunk defines doodad sets.

Doodads in WoW are M2 model files. There are 32 bytes per doodad set, and nSets entries. Doodad sets specify several versions of "interior decoration" for a WMO. Like, a small house might have tables and a bed laid out neatly in one set called "Set_$DefaultGlobal", and have a horrible mess of abandoned broken things in another set called "Set_Abandoned01". The names are only informative.

The doodad set number for every WMO instance is specified in the ADT files. 

Offset 	Type 		Description
0x00 	20 * char 	Set name
0x14 	uint32 		index of first doodad instance in this set
0x18 	uint32 		number of doodad instances in this set
0x1C 	uint32 		unused? (always 0)

struct SMODoodadSet // --Schlumpf 17:03, 31 July 2007 (CEST)
{
/*000h*/  char   name[20];
/*014h*/  UINT32 firstinstanceindex;
/*018h*/  UINT32 numDoodads;
/*01Ch*/  UINT32 nulls;
}

MODN chunk

  • List of filenames for M2 (mdx) models that appear in this WMO.

A block of zero-padded, zero-terminated strings. There are nModels file names in this list. They have to be .MDX!

MODD chunk

  • Information for doodad instances. 40 bytes per doodad instance, nDoodads entries.

While WMOs and models (M2s) in a map tile are rotated along the axes, doodads within a WMO are oriented using quaternions! Hooray for consistency!

I had to do some tinkering and mirroring to orient the doodads correctly using the quaternion, see model.cpp in the WoWmapview source code for the exact transform matrix. It's probably because I'm using another coordinate system, as a lot of other coordinates in WMOs and models also have to be read as (X,Z,-Y) to work in my system. But then again, the ADT files have the "correct" order of coordinates. Weird. 

Offset 	Type 		Description
0x00 	uint16 		Offset to the start of the model's filename in the MODN chunk.
0x02    uint16          Unknown 
0x04 	3 * float 	Position (X,Z,-Y)
0x10 	float 		W component of the orientation quaternion
0x14 	3 * float 	X, Y, Z components of the orientaton quaternion
0x20 	float 		Scale factor
0x24 	4 * uint8 	(B,G,R,A) Lightning-color.

Are you sure the order of the quaternion components is W,X,Y,Z? It seems it is X,Y,Z,W -andhansen 

struct SMODoodadDef // 03-29-2005 By ObscuR
{
  /*000h*/  UINT32 nameIndex
  /*004h*/  float pos[3];
  /*010h*/  float rot[4];
  /*020h*/  float scale;
  /*024h*/  UINT8 color[4];
  /*028h*/
};

MFOG chunk

  • Fog information. Made up of blocks of 48 bytes.
Offset 	Type 		Description
0x00 	uint32 		Flags
0x04 	float[3]	Position
0x10 	float 		Smaller radius
0x14 	float 		Larger radius
0x18 	float 		Fog end
0x1C 	float 		Fog start multiplier (0..1)
0x20 	uint32 		Fog color
0x24 	float 		Unknown (almost always 222.222)
0x28 	float 		Unknown (-1 or -0.5)
0x2C 	uint32 		Color 2

struct SMOFog // 03-29-2005 By ObscuR
{
  /*000h*/  UINT32 flags;		
  /*004h*/  float pos[3];		
  /*008h*/ 	
  /*00Ch*/  		
  /*010h*/  float start[3];		
  /*014h*/  		
  /*018h*/ 		
  /*01Ch*/  float end[3];			
  /*020h*/  	
  /*024h*/   	
  /*028h*/  float fogs[2];
  /*02Ch*/  	
  /*030h*/		
}
  • Fog end: This is the distance at which all visibility ceases, and you see no objects or terrain except for the fog color.
  • Fog start: This is where the fog starts. Obtained by multiplying the fog end value by the fog start multiplier.

MCVP chunk (optional)

  • Convex Volume Planes. Contains blocks of floating-point numbers.

WMO group file

WMO group files contain the actual polygon soup for a particular section of the entire WMO.

Every group file has one top-level MOGP chunk, that has a 68-byte header followed by more subchunks. So it can be effectively treated as a file with a header at 0x14 and chunks starting at 0x58.

MOGP chunk

Offset	Type		Description
0x00 	uint32 		Group name (offset into MOGN chunk)
0x04 	uint32 		Descriptive group name (offset into MOGN chunk)
0x08 	uint32 		Flags
0x0C 	float[3] 	Bounding box corner 1 (same as in MOGI)
0x18 	float[3] 	Bounding box corner 2
0x24 	uint16 		Index into the MOPR chunk
0x26 	uint16 		Number of items used from the MOPR chunk
0x28 	uint16 		Number of batches A
0x2A 	uint16 		Number of batches B
0x2C 	uint32 		Number of batches C
0x30 	uint8[4] 	Up to four indices into the WMO fog list
0x34 	uint32 		LiquidType related, see below in the MLIQ chunk.
0x38 	uint32 		WMO group ID (column 4 in WMOAreaTable.dbc)
0x3C 	uint32 		Always 0?
0x40 	uint32 		Always 0?
  • Struct from WoWModelViewer 0.6
struct WMOGroupHeader {
    int nameStart, nameStart2, flags; 
	float box1[3], box2[3]; 
	short portalStart, portalCount;
	short batches[4];
	uint8 fogs[4];
	int32 unk1, id, unk2, unk3;
};

The fields referenced from the MOPR chunk indicate portals leading out of the WMO group in question.

For the "Number of batches" fields, A + B + C == the total number of batches in the WMO group (in the MOBA chunk). This might be some kind of LOD thing, or just separating the batches into different types/groups...?

Flags: always contain more information than flags in MOGI. I suppose MOGI only deals with topology/culling, while flags here also include rendering info. 

Flag		Meaning
0x1 		something with bounding
0x4 		Has vertex colors (MOCV chunk)
0x8 		Outdoor
0x40
0x200 		Has lights  (MOLR chunk)
0x400		
0x800 		Has doodads (MODR chunk)
0x1000 	        Has water   (MLIQ chunk)
0x2000		Indoor
0x8000
0x20000		Parses some additional chunk. No idea what it is. Oo
0x40000	        Show skybox
0x80000		isNotOcean, LiquidType related, see below in the MLIQ chunk.

MOPY chunk

  • Material info for triangles, two bytes per triangle. So size of this chunk in bytes is twice the number of triangles in the WMO group.
Offset	Type 	Description
0x00 	uint8 	Flags?
0x01 	uint8 	Material ID

struct SMOPoly // 03-29-2005 By ObscuR ( Maybe not accurate :p )
{
	enum  
	{
		F_NOCAMCOLLIDE,
		F_DETAIL,
 		F_COLLISION,
		F_HINT,
		F_RENDER,
		F_COLLIDE_HIT,
	};
/*000h*/  uint8 flags;
/*001h*/  // uint8 lightmapTex; 
/*002h*/  uint8 mtlId;
};

// are you sure it's 3 bytes? wowmapview uses groups of 2 :)  - Z.
// look like the lightmapTex byte is no longer present, this struct come from Alpha :) - Obs

Frequently used flags are 0x20 and 0x40, but I have no idea what they do. 

Flag	Description
0x00 	?
0x01 	?
0x04 	no collision
0x08 	?
0x20 	?
0x40 	?

Material ID specifies an index into the material table in the root WMO file's MOMT chunk. Some of the triangles have 0xFF for the material ID, I skip these. (but there might very well be a use for them?)

The triangles with 0xFF Material ID seem to be a simplified mesh. Like for collision detection or something like that. At least stairs are flattened to ramps if you only display these polys. --shlainn 7 Jun 2009

0xFF representing -1 is used for collision-only triangles. They aren't rendered but have collision. Problem with it: WoW seems to cast and reflect light on them. Its a bug in the engine. --schlumpf_ 20:40, 7 June 2009 (CEST)

Triangles stored here are more-or-less pre-sorted by texture, so it's ok to draw them sequentially.

MOVI chunk

  • Vertex indices for triangles. Three 16-bit integers per triangle, that are indices into the vertex list. The numbers specify the 3 vertices for each triangle, their order makes it possible to do backface culling.

MOVT chunk

  • Vertices chunk. 3 floats per vertex, the coordinates are in (X,Z,-Y) order. It's likely that WMOs and models (M2s) were created in a coordinate system with the Z axis pointing up and the Y axis into the screen, whereas in OpenGL, the coordinate system used in WoWmapview the Z axis points toward the viewer and the Y axis points up. Hence the juggling around with coordinates.

MONR chunk

  • Normals. 3 floats per vertex normal, in (X,Z,-Y) order.

MOTV chunk

  • Texture coordinates, 2 floats per vertex in (X,Y) order. The values range from 0.0 to 1.0. Vertices, normals and texture coordinates are in corresponding order, of course.

MOBA chunk

  • Render batches. Records of 24 bytes.
struct SMOBatch // 03-29-2005 By ObscuR
{
	enum
	{
		F_RENDERED
	};
	?? lightMap;
	?? texture;
	?? bx;
	?? by;
	?? bz;
	?? tx;
	?? ty;
	?? tz;
	?? startIndex;
	?? count;
	?? minIndex;
	?? maxIndex;
	?? flags;
};

For the enUS, enGB versions, it seems to be different from the preceding struct: 

Offset	Type 		Description
0x00 	uint32 		Some color?
0x04 	uint32 		Some color?
0x08 	uint32 		Some color?
0x0C 	uint32 		Start index
0x10 	uint16 		Number of indices
0x12 	uint16 		Start vertex
0x14 	uint16 		End vertex
0x16 	uint8 		0?
0x17 	uint8 		Texture

MOLR chunk

  • Light references, one 16-bit integer per light reference.

This is basically a list of lights used in this WMO group, the numbers are indices into the WMO root file's MOLT table.

For some WMO groups there is a large number of lights specified here, more than what a typical video card will handle at once. I wonder how they do lighting properly. Currently, I just turn on the first GL_MAX_LIGHTS and hope for the best. :(

MODR chunk

  • Doodad references, one 16-bit integer per doodad.

The numbers are indices into the doodad instance table (MODD chunk) of the WMO root file. These have to be filtered to the doodad set being used in any given WMO instance.

MOBN chunk

  • Array of t_BSP_NODE.
struct t_BSP_NODE
{	
	short planetype;          // unsure
	short children[2];        // index of bsp child node(right in this array)   
	unsigned short numfaces;  // num of triangle faces in  MOBR
	unsigned short firstface; // index of the first triangle index(in  MOBR)
	short nUnk;	          // 0
	float fDist;    
};
// The numfaces and firstface define a polygon plane.
                                        2005-4-4 by linghuye

This+BoundingBox(in wmo_root.MOGI) is used for Collision --Tigurius

MOBR chunk

  • Triangle indices (in MOVI which define triangles) to describe polygon planes defined by MOBN BSP nodes.

MOCV chunk

  • Vertex colors, 4 bytes per vertex (BGRA), for WMO groups using indoor lighting.

I don't know if this is supposed to work together with, or replace, the lights referenced in MOLR. But it sure is the only way for the ground around the goblin smelting pot to turn red in the Deadmines. (but some corridors are, in turn, too dark - how the hell does lighting work anyway, are there lightmaps hidden somewhere?)

- I'm pretty sure WoW does not use lightmaps in it's WMOs...

After further inspection, this is it, actual pre-lit vertex colors for WMOs - vertex lighting is turned off. This is used if flag 0x2000 in the MOGI chunk is on for this group. This pretty much fixes indoor lighting in Ironforge and Undercity. The "light" lights are used only for M2 models (doodads and characters). (The "too dark" corridors seemed like that because I was looking at it in a window - in full screen it looks pretty much the same as in the game) Now THAT's progress!!!

MLIQ chunk

  • Specifies liquids inside WMOs.

This is where the water from Stormwind and BFD etc. is hidden. (slime in Undercity, pool water in the Darnassus temple, some lava in IF)

Chunk header: 

Offset	Type 		Description
0x00 	uint32 		number of X vertices (xverts)
0x04 	uint32 		number of Y vertices (yverts)
0x08 	uint32 		number of X tiles (xtiles = xverts-1)
0x0C 	uint32 		number of Y tiles (ytiles = yverts-1)
0x10 	float[3] 	base coordinates?
0x1C 	uint16 		material ID

The liquid data contains the vertex height map (xverts * yverts * 8 bytes) and the tile flags (xtiles * ytiles bytes) as descripbed in ADT files (MCLQ chunk). The length and width of a liquid tile is the same as on the map, that is, 1/8th of the length of a map chunk. (which is in turn 1/16th the length of a map tile).

  • the real deal

The LiquidType in the DBC is determined as follows:

If var_0x3C in the root's MOHD has the 4 bit (&4), it will take the variable in MOGP's var_0x34. If not, it checks var_0x34 for 15 (green lava). If that is set, it will take 0, else it will take var_0x34 + 1.

The result of this (0,var_0x34 or var_0x34+1) will be checked if above 21 (naxxramas slime). If yes, the entry is stored as given. Else, it will be checked for the type (ocean, water, magma, slime). Ocean might be overwritten by MOGP flags being & 0x80000.

  • tl;dr

MOGP.var_0x34 is LiquidType. This will be overwritten with the "WMO *" liquid types in case, this is below 21 (naxxramas slime). Additionally, it will be taken +1 if the flag in the root's header is not set.

  • old:

The material ID often refers to what seems to be a "special" material in the root WMO file (special because it often has a solid color/placeholder texture, or a texture from XTextures\*) - but sometimes the material referenced seems to be not special at all, so I'm not really sure how the liquid material is obtained - such as water/slime/lava.

Unknown Chunk

(Yes, I don't even know the identifier. But it is there.)

There are size>>1 entries in it. It modifies the vertices indexes or something.

Unknown Chunk 2

(Again, I don't know what this is..)

There are MOBA.nEntries entries of 8 bytes. 

0x00	uint32
0x04	uint16				// yah, its still somehow 8 bytes. I guess the remaining bytes are used elsewhere.


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