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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/v17 files, actually:

  • WMO root file - lists textures (BLP Files), doodads (M2 or MDX Files), etc., and orientation for the WMO/v17 groups
  • WMO group file - 3d model data for one unit in the world map object

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

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

There is a hardcoded maximum of 512 group files per root object.

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.
struct SMOHeader
/*000h*/  uint32_t nTextures;    
/*004h*/  uint32_t nGroups;    
/*008h*/  uint32_t nPortals;   
/*00Ch*/  uint32_t nLights;    
/*010h*/  uint32_t nDoodadNames; 
/*014h*/  uint32_t nDoodadDefs;                                    // *
/*018h*/  uint32_t nDoodadSets;    
/*01Ch*/  CArgb ambColor;                        // Color settings for base (ambient) color. See the flag at /*03Ch*/.   
/*020h*/  foreign_key<uint32_t, &WMOAreaTableRec::m_WMOID> wmoID;
/*024h*/  CAaBox bounding_box;
/*03Ch*/  uint16_t flag_attenuate_vertices_based_on_distance_to_portal : 1;
/*03Ch*/  uint16_t flag_skip_base_color : 1;                       // do not add base (ambient) color (of MOHD) to MOCVs. apparently does more, e.g. required for multiple MOCVs
/*03Ch*/  uint16_t flag_use_liquid_type_dbc_id : 1;                // use real liquid type ID from DBCs instead of local one. See MLIQ for further reference.
/*03Ch*/  uint16_t flag_lighten_interiors : 1;                     // makes iterior groups much brighter, effects MOCV rendering. Used e.g.in Stormwind for having shiny bright interiors,
/*03Ch*/  uint16_t Flag_Lod : 1;                                   // ≥ Legion (20740) 
/*03Ch*/  uint16_t : 11;                                           // unused as of Legion (20994)
/*03Eh*/  uint16_t numLod;                                         // ≥ Legion (21108)  includes base lod (→ numLod = 3 means '.wmo', 'lod0.wmo' and 'lod1.wmo')
} header;

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.

char texture_filenames[];

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
  uint32_t F_UNLIT : 1;                    // disable lighting logic in shader (but can still use vertex colors)
  uint32_t F_UNFOGGED : 1;                 // disable fog shading (rarely used)
  uint32_t F_UNCULLED : 1;                 // two-sided
  uint32_t F_EXTLIGHT : 1;                 // darkened, the intern face of windows are flagged 0x08
  uint32_t F_SIDN  : 1;                    // (bright at night, unshaded) (used on windows and lamps in Stormwind, for example) (see emissive color)
  uint32_t F_WINDOW : 1;                   // lighting related (flag checked in CMapObj::UpdateSceneMaterials)
  uint32_t F_CLAMP_S : 1;                  // tex clamp S (force this material's textures to use clamp s addressing)
  uint32_t F_CLAMP_T : 1;                  // tex clamp T (force this material's textures to use clamp t addressing)
  uint32_t flag_0x100 : 1;
  uint32_t : 23;                           // unused as of
/*004h*/  uint32_t shader;                 // Index into CMapObj::s_wmoShaderMetaData. See below (shader types).
/*008h*/  uint32_t blendMode;              // Blending: see Blend_State_Table
/*00Ch*/  uint32_t diffuseNameIndex;       // offset into MOTX
/*010h*/  CImVector emissive_color;        // emissive color; see below (emissive color)
/*014h*/  CImVector sidn_emissive_color;   // set at runtime; gets sidn-manipulated emissive color; see below (emissive color)
/*018h*/  uint32_t envNameIndex;
/*01Ch*/  uint32_t diffColor;
/*020h*/  foreign_key<uint32_t, &TerrainTypeRec::m_ID> ground_type;            // according to CMapObjDef::GetGroundType
/*024h*/  uint32_t texture_2;
/*028h*/  uint32_t color_2;
/*02Ch*/  uint32_t flags_2;
/*030h*/  uint32_t runTimeData[4];         // This data is explicitly nulled upon loading. Contains textures or similar stuff.
} materials[];

texture_1, 2 and 3 are start positions for texture filenames in the MOTX data block ; texture_1 for the first texture, texture_2 for the second (see shaders), etc. texture_1 defaults to "createcrappygreentexture.blp".

color_2 is diffuse color : CWorldView::GatherMapObjDefGroupLiquids(): geomFactory->SetDiffuseColor((CImVector*)(smo+7));

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.

Texture addressing

By default, textures used by WMO materials are assigned an addressing mode of EGxTexWrapMode::GL_REPEAT (ie wrap mode).

SMOMaterial flags flag_tex_clamp_s and flag_tex_clamp_t can override this default to clamp mode for the S and T dimensions, respectively.

Emissive color

The emissive_color CImVector at offset 0x10 is used with the SIDN (self-illuminated day night) scalar from CDayNightObject to light exterior window glows (see flag 0x10 above).

The scalar is interpolated out of a static table in the client, based on the time of day.

The color value eventually is copied into offset 0x14 (sidn_emissive_color) after being manipulated by the SIDN scalar. This manipulation occurs in CMapObj::UpdateMaterials.

Shader types (15464)

Depending on the shader, a different amount of textures is required. If there aren't enough filenames given, it defaults to Opaque (with one filename). More filenames than required are just ignored.

Data is from 15464.

value name textures without shader textures with shader texcoord count color count
0 Diffuse 1 1 1 1
1 Specular 1 1 1 1
2 Metal 1 1 1 1
3 Env 1 2 1 1
4 Opaque 1 1 1 1
5 EnvMetal 1 2 1 1
6 TwoLayerDiffuse 1 2 2 2
7 TwoLayerEnvMetal 1 3 2 2
8 TwoLayerTerrain 1 2 1 2 automatically adds _s in the filename of the second texture
9 DiffuseEmissive 1 2 2 2
10 1 1 1 1 SMOMaterial::SH_WATERWINDOW -- Seems to be invalid. Does something with MOTA (tangents).
11 MaskedEnvMetal 1 3 2 2
12 EnvMetalEmissive 1 3 2 2
13 TwoLayerDiffuseOpaque 1 2 2 2
14 TwoLayerDiffuseEmissive 1 1 1 1 SMOMaterial::SH_SUBMARINEWINDOW -- Seems to be invalid. Does something with MOTA (tangents).
15 1 2 2 2
16 Diffuse 1 1 1 1 SMOMaterial::SH_DIFFUSE_TERRAIN -- "Blend Material": used for blending WMO with terrain (dynamic blend batches)

tex coord and color count decide vertex buffer format: EGxVertexBufferFormat_PNC2T2

Shader types (18179)

value #textures without shader #textures with shader texcoord count color count
0 - Diffuse 1 1 1 1
1 - Specular 1 1 1 1
2 - Metal 1 1 1 1
3 - Env 1 2 1 1
4 - Opaque 1 1 1 1
5 - EnvMetal 1 2 1 1
6 - TwoLayerDiffuse 1 2 2 2
7 - TwoLayerEnvMetal 1 3 2 2
8 - TwoLayerTerrain 1 2 1 2 automatically adds _s in the filename of the second texture
9 - DiffuseEmissive 1 2 2 2
10 - waterWindow 1 1 1 1 SMOMaterial::SH_WATERWINDOW -- automatically generates MOTA
11 - MaskedEnvMetal 1 3 2 2
12 - EnvMetalEmissive 1 3 2 2
13 - TwoLayerDiffuseOpaque 1 2 2 2
14 - submarineWindow 1 1 1 1 SMOMaterial::SH_SUBMARINEWINDOW -- automatically generates MOTA
15 - TwoLayerDiffuseEmissive 1 2 2 2
16 - DiffuseTerrain 1 1 1 1 SMOMaterial::SH_DIFFUSE_TERRAIN -- "Blend Material": used for blending WMO with terrain (dynamic blend batches)
17 - AdditiveMaskedEnvMetal 1 3 2 2

void CMapObj::CreateMaterial (unsigned int materialId)

void CMapObj::CreateMaterial (unsigned int materialId)
  assert (m_materialCount);
  assert (m_materialTexturesList);
  assert (materialId < m_materialCount);

  if (++m_materialTexturesList[materialId].refcount <= 1)
    SMOMaterial* material = &m_smoMaterials[materialId];

    const char* texNames[3];
    texNames[0] = &m_textureFilenamesRaw[material->firstTextureOffset];
    texNames[1] = &m_textureFilenamesRaw[material->secondTextureOffset];
    texNames[2] = &m_textureFilenamesRaw[material->thirdTextureOffset];
    if ( *texNames[0] )
      texNames[0] = "createcrappygreentexture.blp";

    assert (material->shader < SMOMaterial::SH_COUNT);

    int const textureCount
      ( CShaderEffect::s_enableShaders
      ? s_wmoShaderMetaData[material->shader].texturesWithShader
      : s_wmoShaderMetaData[material->shader].texturesWithoutShader

    int textures_set (0);

    for (; textures_set < textureCount; ++textures_set)
      if (!texNames[textures_set])
        material->shader = MapObjOpaque;
        textures_set = 1;

    for (; textures_set < 3; ++textures_set)
      texNames[textures_set] = nullptr;

    if (material->shader == MapObjTwoLayerTerrain && texNames[1])
      texNames[1] = insert_specular_suffix (texNames[1]);

    int flags (std::max (m_field_2C, 12));

    const char* parent_name (m_field_9E8 & 1 ? m_filename : nullptr);

    m_materialTexturesList[materialId]->textures[0] = texNames[0] ? CMap::CreateTexture (texNames[0], parent_name, flags) : nullptr;
    m_materialTexturesList[materialId]->textures[1] = texNames[1] ? CMap::CreateTexture (texNames[1], parent_name, flags) : nullptr;
    m_materialTexturesList[materialId]->textures[2] = texNames[2] ? CMap::CreateTexture (texNames[2], parent_name, flags) : nullptr;

MOGN chunk

  • List of group names for the groups in this map object.
char group_names[];

A contiguous block of zero-terminated strings. The names are purely informational except for "antiportal". The names are referenced from MOGI and MOGP.

There are not always nGroups entries in this chunk as it contains extra empty strings and descriptive names. It (always ?) begins with two empty strings, so 0x00 0x00, and is 4-byte padded at the end of the chunk only. The names are indeed referenced in MOGI, and both the name and a descriptive name are referenced in the group file header (2 firsts uint16 of MOGP).

MOGI chunk

  • Group information for WMO groups, 32 bytes per group, nGroups entries.
struct SMOGroupInfo
#if version < ? 
  uint32_t offset;
  uint32_t size;
/*000h*/  uint32_t flags;      //  see information in in MOGP, they are equivalent
/*004h*/  CAaBox bounding_box;
/*01Ch*/  int32_t nameoffset;  // name in MOGN chunk (-1 for no name)
} groups[];

Groups don't have placement or orientation information, because the coordinates for the vertices in the additional .WMO/v17 files are already correctly transformed relative to (0,0,0) which is the entire WMO/v17's base position in model space.

The name offsets point to the position in the file relative to the MOGN header.

MOSB chunk

  • Skybox. Contains an zero-terminated filename for a skybox. (padded to 4 byte alignment if "empty"). If the first byte is 0, the skybox flag in all MOGI entries are cleared and there is no skybox.
char skybox_filename[];

MOPV chunk

  • Portal vertices, one entry is a float[3], usually 4 * 3 * float per portal (actual number of vertices given in portal entry)
C3Vector portal_vertices[];

Portals are polygon planes (usually quads, but they can have more complex shapes) that specify where separation points between groups in a WMO/v17 are - these are usually doors or entrances, but can be placed elsewhere. Portals are used for occlusion culling, and is a known rendering technique used in many games (among them Unreal Tournament 2004 and Descent. See Portal Rendering on Wikipeda and Antiportal on Wikipedia for more information.

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/v17 using this and the MOPR chunk. This could be used to speed up the rendering once/if I figure out how.

This image explains how portal equation in MOPT and relations in MOPR are connected: Portal explanation. Deamon (talk) 17:06, 23 February 2017 (CET)

MOPT chunk

  • Portal information. 20 bytes per portal, nPortals entries. There is a hardcoded maximum of 128 portals in a single WMO.
struct SMOPortal
  uint16_t base_index;
  uint16_t index_count;
  C4Plane  plane;
} portals[];

This structure describes one portal separating two WMO groups. A single portal is usually made up of four vertices in a quad (starting at base_index and going to base_index + index_count). However, portals support more complex shapes, and can fully encompass holes such as the archway leading into Ironforge and parts of the Caverns of Time.

It is likely that portals are drawn as GL_TRIANGLE_STRIP in WoW's occlusion pipeline, since some portals have a vertex count that is not evenly divisible by four. One example of this is portal #21 in CavernsOfTime.wmo from Build #5875 (WoW 1.12.1), which has 10 vertices.

MOPR chunk

  • Map Object Portal References from groups. Mostly twice the number of portals. Actual count defined by sum (MOGP.portals_used).
struct SMOPortalRef // 04-29-2005 By ObscuR
  uint16_t portal_index;  // into MOPR
  uint16_t group_index;   // the other one
  int16_t side;           // positive or negative.
  uint16_t unk;
} portal_references[];

MOVV chunk

  • Visible block vertices, 0xC byte per entry.

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

C3Vector visible_block_vertices[];

MOVB chunk

  • Visible block list
  uint16_t firstVertex;
  uint16_t count;
) visible_blocks[];

MOLT chunk

  • Lighting information. 48 bytes per light, nLights entries
struct SMOLight
  enum LightType
    OMNI_LGT = 0,
    SPOT_LGT = 1,
    DIRECT_LGT = 2,
    AMBIENT_LGT = 3,
  /*000h*/  uint8_t type;
  /*001h*/  uint8_t useAtten;
  /*002h*/  uint8_t pad[2];
  /*004h*/  CImVector color;
  /*008h*/  C3Vector position;
  /*014h*/  float intensity;
  /*018h*/  float attenStart;
  /*01Ch*/  float attenEnd;
  /*020h*/  float unk[4];
} lights[];

First 4 uint8_t are probably flags, mostly with the values (0,1,1,1).

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/v17 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/v17 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/v17 local lights... :)

The entire MOLT and related chunks seem to be unused at least in 3.3.5a. Changing light colors and other settings on original WMOs leads to no effect. Removing the light leads to no effect either. I assume that MOLT rendering is disabled somewhere in the WoW.exe, as it might use the same principle as the M2 light emitters which are not properly supported up to WoD. However, when you explore the WMOs in 3D editors you can clearly see that MOCV layer is different under those lamps. So, I assume they are used for baking MOCV colors and also written to the actual file in case the renderer will ever get updated, or just because you can easily import the WMO back and rebake the colors. --- Skarn (talk)

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/v17. 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.

struct SMODoodadSet
/*000h*/  char     name[20];            // set name
/*014h*/  uint32_t firstinstanceindex;  // index of first doodad instance in this set
/*018h*/  uint32_t numDoodads;          // number of doodad instances in this set
/*01Ch*/  uint32_t unused;
} doodad_sets[];

firstinstanceindex is not the name index, but the actual order the doodads come in the MODD chunk in the WMO -MaiN

MODN chunk

  • List of filenames for M2 (mdx) models that appear in this WMO/v17.

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

char doodad_filenames[];

MODD chunk

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

-- There are not nDoodads entries here! Divide the chunk length by 40 to get the correct amount.

While WMO/v17s and models (M2s) in a map tile are rotated along the axes, doodads within a WMO/v17 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 WMO/v17s 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.

struct SMODoodadDef
  /*000h*/  uint32_t name_offset : 24;        // reference offset into MODN
  /*003h*/  uint32_t flag_AcceptProjTex : 1;
  /*003h*/  uint32_t flag_0x2 : 1;            // MapStaticEntity::field_34 |= 1 (if set, MapStaticEntity::AdjustLighting is _not_ called)
  /*003h*/  uint32_t flag_0x4 : 1;
  /*003h*/  uint32_t flag_0x8 : 1;
  /*003h*/  uint32_t : 4;                     // unused as of
  /*004h*/  C3Vector position;                // (X,Z,-Y)
  /*010h*/  C4Quaternion orientation;         // (X, Y, Z, W)
  /*020h*/  float scale;                      // scale factor
  /*024h*/  CImVector color;                 // (B,G,R,A) diffuse lighting color, used in place of global diffuse from DBCs
} doodad_definitions[];

It looks like in order to get correct picture the color from SMODoodadDef should be applied only to opaque submeshes of M2. Deamon (talk)

  • How to compute a matrix to map WMO's M2 to world coordinates

The coordinate system here is WMO's local coordinate system. It's Z-up already, that differs it from Y-up in MODF(ADT), MODF(WDT) and MDDF chunks. To compute the whole placement matrix for doodad you would need take positionMatrix of WMO from MODF(ADT) or MODF(WDT) and multiply it by positionMatrix calculated here.

Example implementation in js with gl-matrix library:

 function createPlacementMatrix(modd, wmoPlacementMatrix){
     var placementMatrix = mat4.create();
     mat4.multiply(placementMatrix, placementMatrix, wmoPlacementMatrix);
     mat4.translate(placementMatrix, placementMatrix, [modd.pos[0],modd.pos[1], modd.pos[2]]);
     var orientMatrix = mat4.create();
         [modd.rotation[0], //imag.x
         modd.rotation[1],  //imag.y,
         modd.rotation[2],  //imag.z,
         modd.rotation[3]   //real
     mat4.multiply(placementMatrix, placementMatrix, orientMatrix);
     mat4.scale(placementMatrix, placementMatrix, [modd.scale, modd.scale, modd.scale]);
     return placementMatrix;

MFOG chunk

  • Fog information. Made up of blocks of 48 bytes.
struct SMOFog
  /*000h*/  uint32_t flag_infinite_radius : 1; // F_IEBLEND: Ignore radius in CWorldView::QueryCameraFog
  /*000h*/  uint32_t : 3;                      // unused as of
  /*000h*/  uint32_t flag_0x10 : 1;
  /*000h*/  uint32_t : 27;                     // unused as of
  /*004h*/  C3Vector pos;
  /*010h*/  float smaller_radius;              // start
  /*014h*/  float larger_radius;               // end
  /*018h*/    float end;
  /*01Ch*/    float start_scalar;              // (0..1)
  /*020h*/    CImVector color;                // The back buffer is also cleared to this colour
            } fog;
  /*024h*/    float end;
  /*028h*/    float start_scalar;              // (0..1)
  /*02Ch*/    CImVector color;
            } underwater_fog;
} fogs[];
  • 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.
  • There should always be at least one fog entry in MFOG. The empty fog entry has both radiuses set to zero, 444.4445 for end, 0.25 for start_scalar, 222.2222 for underwater end, -0.5 for underwater start_scalar.

MCVP chunk (optional)

  • Convex Volume Planes. Contains blocks of floating-point numbers. 0x10 bytes (4 floats) per entry.
C4Plane convex_volume_planes[];   // normal points out

These are used to define the volume of when you are inside this WMO. Important for transports. If a point is behind all planes (i.e. point-plane distance is negative for all planes), it is inside.

GFID (Legion+)

  • required when WMO is load from fileID (e.g. game objects)
struct {
    uint32 id[MOHD.nGroups];
} groupFileDataIDs[ !MOHD.Flag_Lod ? 1
                  : MOHD.numLod ? MOHD.numLod : 3   // fallback for missing numLod: assume numLod=2+1base

WMO group file

WMO group files contain the actual polygon soup for a particular section of the entire WMO/v17.

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.

The subchunks are not always present. Some are fixed and needed while others are only checked for if some flags in the header are set. The chunks need to be in the right order if you want WoW to read it.

The following chunks are always present in the following order:

These chunks are only present if a flag in the header is set. See the list below for the flags.

MOGP chunk

Note: In its header is given a wrong size. Just use 0x44. -eLaps

  • Actually, the size is correct, the other chunks are just subchunks of MOGP :) ---Tigurius
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 		transBatchCount
0x2A 	uint16 		intBatchCount
0x2C 	uint16 		extBatchCount
0x2E 	uint16 		unk(padding? batch type D?) 
0x30 	uint8[4] 	Up to four indices into the WMO fog list
0x34 	uint32 		LiquidType, not always directly used: see below in the MLIQ chunk.
0x38 	foreign_key<uint32_t, &WMOAreaTableRec::m_WMOGroupID> 		WMO group ID
0x3C 	uint32 		&1: WoD(?)+ CanCutTerrain (by MOPL planes), others (UNUSED: 20740)
0x40 	uint32 		(UNUSED: 20740)

The fields referenced from the MOPR chunk indicate portals leading out of the WMO/v17 group in question.

For the "Number of batches" fields, A + batches_interior + batches_exterior == the total number of batches in the WMO/v17 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.

group flags

Flag		Meaning
0x1		Has MOBN and MOBR chunk.
0x2		Has light map (MOLM, MOLD). (UNUSED: 20740) possibly: subtract mohd.color in mocv fixing 
0x4 		Has vertex colors (MOCV chunk).
0x8 		SMOGroup::EXTERIOR -- Outdoor - also influences how doodads are culled
0x10		(UNUSED: 20740)
0x20		(UNUSED: 20740)
0x40            "Do not use local diffuse lightning". Applicable for both doodads from this wmo group(color from MODD) and water(CWorldView::GatherMapObjDefGroupLiquids). 
0x200 		Has lights  (MOLR chunk)
0x400		<= Cataclysm: Has MPBV, MPBP, MPBI, MPBG chunks, neither 3.3.5a nor Cataclysm alpha actually use them though, but just skips them. Legion+(?): SMOGroup::LOD: Also load for LoD != 0 (_lod* groups)
0x800 		Has doodads (MODR chunk)
0x1000		SMOGroup::LIQUIDSURFACE -- Has water   (MLIQ chunk)
0x2000		SMOGroup::INTERIOR -- Indoor
0x4000		(UNUSED: 20740)
0x10000         SMOGroup::ALWAYSDRAW -- clear 0x8 after CMapObjGroup::Create() in MOGP and MOGI
0x20000		(UNUSED: 20740) Has MORI and MORB chunks.
0x40000		Show skybox -- automatically unset if MOSB not present.
0x80000		is_not_water_but_ocean, LiquidType related, see below in the MLIQ chunk.
0x200000	IsMountAllowed
0x400000	(UNUSED: 20740)
0x1000000	SMOGroup::CVERTS2: Has two MOCV chunks: Just add two or don't set 0x4 to only use cverts2.
0x2000000	SMOGroup::TVERTS2: Has two MOTV chunks: Just add two.
0x4000000	SMOGroup::ANTIPORTAL: Just call CMapObjGroup::CreateOccluders() independent of groupname being "antiportal". requires intBatchCount == 0, extBatchCount == 0, UNREACHABLE.
0x8000000	unk. requires intBatchCount == 0, extBatchCount == 0, UNREACHABLE.
0x10000000	(UNUSED: 20740)
0x20000000	(UNUSED: 20740)
0x40000000	SMOGroup::TVERTS3: Has three MOTV chunks, eg. for MOMT with shader 18.


If a group wmo is named "antiportal", CMapObjGroup::CreateOccluders() is called and group flags 0x4000000 and 0x80 are set automatically in both, MOGP and MOGI. Also, the BSP tree is cleared and batch_count[interior] and [exterior] is set to 0. If flags & 0x4000000 is set, just CMapObjGroup::CreateOccluders() is called, without setting flags or clearing bsp.

void CMapObjGroup::CreateOccluders()
  for ( unsigned int mopy_index (0), movi_index (0)
      ; mopy_index < this->mopy_count
      ; ++mopy_index, ++movi_index
    C3Vector* points[3] = 
      { &this->m_vertices[this->movi[movi_index].points[0]]
      , &this->m_vertices[this->movi[movi_index].points[1]]
      , &this->m_vertices[this->movi[movi_index].points[2]]

    float avg ((points[0]->z + points[1]->z + points[2]->z) / 3.0); 

    unsigned int two_points[2];
    unsigned int two_points_index (0);

    for (unsigned int i (0); i < 3; ++i)
      if (points[i]->z > avg)
        two_points[two_points_index++] = i;

    if (two_points_index > 1)
      CMapObjOccluder* occluder (CMapObj::AllocOccluder());
      occluder->p1 = points[two_points[0]];
      occluder->p2 = points[two_points[1]];

      append (this->occluders, occluder);

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.
struct SMOPoly
    uint8_t F_UNK_0x01: 1;
    uint8_t F_NOCAMCOLLIDE : 1;
    uint8_t F_DETAIL : 1;
    uint8_t F_COLLISION : 1;
    uint8_t F_HINT : 1;
    uint8_t F_RENDER : 1;
    uint8_t F_UNK_0x40 : 1;
    uint8_t F_COLLIDE_HIT : 1;

    bool isTransFace() { return F_UNK_0x01 && (F_DETAIL || F_RENDER); }
    bool isColor() { return !F_COLLISION; }
    bool isRenderFace() { return F_RENDER && !F_DETAIL; }
    bool isCollidable() { return F_COLLISION || isRenderFace(); }
  } flags;

#if version < ?
  uint8_t lightmapTex;
  uint8_t material_id;           // index into MOMT, 0xff for collision faces
#if version < ?
  uint8_t padding;

0xFF 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., count = size / sizeof(unsigned short). 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., count = size / (sizeof(float) * 3). 3 floats per vertex, the coordinates are in (X,Z,-Y) order. It's likely that WMO/v17s 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. count = size / (sizeof(float) * 3). 3 floats per vertex normal, in (X,Z,-Y) order.

MOTV chunk

  • Texture coordinates, 2 floats per vertex in (X,Y) order. The values usually range from 0.0 to 1.0, but it's ok to have coordinates out of that range. Vertices, normals and texture coordinates are in corresponding order, of course. Not present in antiportal WMO groups.

MOBA chunk

  • Render batches. Records of 24 bytes.
struct SMOBatch
#if version < ?
  uint8_t lightMap;
  uint8_t texture;
#if  < Legion
  /*0x00*/ int16_t unknown_box_min[3];              // -2,-2,-1, 2,2,3 in cameron -> seems to be a bounding box for culling
  /*0x06*/ int16_t unknown_box_max[3];
  /*0x00*/ uint8_t unknown[0xA];
  /*0x0A*/ uint16_t material_id_large;              // used if flag_use_uint16_t_material is set.
#if version < ?
  uint16_t first_index;                             // index of the first face index used in MOVI
  /*0x0C*/ uint32_t first_index;                    // index of the first face index used in MOVI
  /*0x10*/ uint16_t num_indices;                    // number of MOVI indices used
  /*0x12*/ uint16_t first_vertex;                   // index of the first vertex used in MOVT
  /*0x14*/ uint16_t last_vertex;                    // index of the last vertex used (batch includes this one)
  /*0x16*/ uint8_t flag_unknown_1 : 1;
#if ≥ Legion 
  /*0x16*/ uint8_t flag_use_material_id_large : 1;  // instead of material_id use material_id_large
#if version >= ?
  /*0x17*/ uint8_t material_id;                     // index in MOMT
  uint8_t padding;

Batches are groups of faces with the same material ID in root's MOMT, and they're used to accelerate rendering. Note that the client doesn't use them in the same way while rendering in D3D or OpenGL (only D3D uses all batches information). The vertex buffer containing vertices from first_vertex to last_vertex can contain vertices that aren't used by the batch. On the other hand, if one of the faces used need a vertex, it has to be in the buffer. Concerning the byte at 0x16, as a material ID is coded on a uint8, I guess it is completely unused. --Gamhea 12:23, 29 July 2013 (UTC)


This seems to be a low resolution bounding box of the contained vertices. The client appears to be using them to do batch-level culling, so if they are set incorrectly, the batch may be randomly disappearing. According to Adspartan (talk), the box can be calculated by just iterating over all vertices contained (by following first_vertex and last_vertex to MOVT and taking the minimum/maximum of those. They should probably be rounded away from zero instead of being truncated on conversion to int16_t.

This section only applies to versions ≥ Legion .

unknown_box seems no longer used (and nulled). Instead, flag_use_material_id_large can be set to use material_id_large which was the last of unknown_box's fields. This means that when "retroporting" files, unknown_box's values need to be calculated (by building minimum and maximum from the corresponding vertices) and material_id should be set, if it can fit a uint8_t. --based on Rangorn (talk)

MOLR chunk

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

This is basically a list of lights used in this WMO/v17 group, the numbers are indices into the WMO/v17 root file's MOLT table.

For some WMO/v17 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/v17 root file. These have to be filtered to the doodad set being used in any given WMO/v17 instance.

MOBN chunk

  • Nodes of the BSP tree, used for collision (along with bounding boxes ?). Array of t_BSP_NODE. / CAaBspNode. 0x10 bytes.
struct t_BSP_NODE
  uint16_t planeType;    // 4: leaf, 0 for YZ-plane, 1 for XZ-plane, 2 for XY-plane
  int16_t  children[2];  // index of bsp child node (right in this array)
  uint16_t numFaces;     // num of triangle faces in MOBR
  uint32_t firstFace;    // index of the first triangle index(in MOBR)
  float    fDist;

planetype might be 0 for YZ-plane, 1 for XZ-plane, 2 for XY-plane, 4 for BSP leaf. fDist is where split plane locates based on planetype, ex, you have a planetype 0 and fDist 15, so the split plane is located at offset ( 15, 0, 0 ) with Normal as ( 1, 0, 0 ), I think the offset is relative to current node's bounding box center. The BSP root ( ie. node 0 )'s bounding box is the WMO's boundingbox, then you subdivide it with plane and fdist, then you got two children with two bounding box, and so on. you got the whole BSP tree. As the bsp leaf might overlapping the dividing plane, i think you might have two same face exist on two different bsp leaf. I'll make further tests to prove this. --mobius.

The biggest leaf in terms of number of faces in 3.3.5 contains more than 2100 faces (some ice giant in the Storm Peaks), so it's not advised to use more. (While I haven't investigated properly, there might be a limit at 8192 in --Schlumpf (talk) 11:18, 3 January 2016 (UTC))

fDist is relative to point (0,0,0) of whole WMO. children[0] is child on negative side of dividing plane, children[1] is on positive side. --Deamon (talk) 10:01, 15 January 2016 (UTC)

#define epsilon 0.01F
void MergeBox(CVect3 (&result)[2], float  *box1, float  *box2)
 result[0][0] = box1[0];
 result[0][1] = box1[1];
 result[0][2] = box1[2];
 result[1][0] = box2[0];
 result[1][1] = box2[1];
 result[1][2] = box2[2];
void AjustDelta(CVect3 (&src)[2], float *dst, float coef)
 float d1 = (src[1][0]- src[0][0]) * coef;// delta x
 float d2 = (src[1][1]- src[0][1]) * coef;// delta y
 float d3 = (src[1][2]- src[0][2]) * coef;// delta z
 dst[1] = d1 + src[0][1];
 dst[0] = d2 + src[0][0];
 dst[2] = d3 + src[0][2];
void TraverseBsp(int iNode, CVect3 (&pEyes)[2] , CVect3 (&pBox)[2],void *(pAction)(T_BSP_NODE *,void *param),void *param)
 int plane;
 float eyesmin_boxmin;
 float boxmax_eyesmax;
 float eyesmin_fdist;
 float eyes_max_fdist;
 float eyesmin_div_deltadist;
 CVect3 tBox1[2];
 CVect3 tBox2[2];
 CVect3 newEyes[2];
 CVect3 ajusted;
 T_BSP_NODE *pNode = &m_tNode[iNode];
 if ( pNode)
  if (pNode->planetype & 4 )
   if(pAction == 0)
  plane =pNode->planetype  & 3;
  eyesmin_boxmin = pEyes[0][plane] - pBox[0][plane];
  if ( ( -epsilon < eyesmin_boxmin) | (-epsilon == eyesmin_boxmin) || (pEyes[1][plane]- pBox[0][plane])  >= -epsilon )
   boxmax_eyesmax = pBox[1][plane] - pEyes[1][plane];
   if ( (epsilon < boxmax_eyesmax) | (epsilon == boxmax_eyesmax) || (pBox[1][plane] -  pEyes[0][plane]) >= epsilon )
    tBox1[0][plane] = pNode->fDist;
    tBox2[1][plane] = pNode->fDist;
    eyesmin_fdist = pEyes[0][plane] - pNode->fDist;
    eyes_max_fdist = (pEyes[1][plane]) - pNode->fDist;
    if ( eyesmin_fdist >= -epsilon && eyesmin_fdist <= epsilon|| (eyes_max_fdist >= -epsilon) && eyes_max_fdist <= epsilon )
     if ( pNode->children[1] != (short)-1 ) TraverseBsp(pNode->children[1],  pEyes,  tBox1,pAction,param);
     if ( pNode->children[0] != (short)-1 ) TraverseBsp(pNode->children[0] , pEyes, tBox2,pAction,param);
    if ( eyesmin_fdist > epsilon && eyes_max_fdist < epsilon)
      if ( pNode->children[1] != (short)-1 ) TraverseBsp(pNode->children[1], pEyes, tBox1,pAction,param);
    if ( eyesmin_fdist < -epsilon && eyes_max_fdist < -epsilon)
      if ( pNode->children[0] != (short)-1 ) TraverseBsp(pNode->children[0] , pEyes, tBox2,pAction,param);
    eyesmin_div_deltadist = (float)(eyesmin_fdist / (eyesmin_fdist - eyes_max_fdist));
    AjustDelta(pEyes, ajusted, eyesmin_div_deltadist);
    if ( eyesmin_fdist <= 0.0 )
     if ( pNode->children[0]  != (short)-1 )
      MergeBox(newEyes, &pEyes[0][0], ajusted);
      TraverseBsp(pNode->children[0] , newEyes, tBox2,pAction,param);
     if (pNode->children[1]  != (short)-1 )
      MergeBox(newEyes, ajusted, &pEyes[1][0]);
      TraverseBsp(pNode->children[1] , newEyes, tBox1,pAction,param);
     if ( pNode->children[1]  != (short)-1 )
      MergeBox(newEyes, &pEyes[0][0], ajusted);
      TraverseBsp(pNode->children[1] , newEyes, tBox1,pAction,param);
     if (pNode->children[0]  != (short)-1 )
      MergeBox(newEyes, ajusted, &pEyes[1][0]);
      TraverseBsp(pNode->children[0] , newEyes, tBox2,pAction,param);
CheckFromEyes(CVect3 (&pEyes)[2],void *(pAction)(T_BSP_NODE *,void *param),void *param )
/*CVect3 eyes[2];
eyes[0] = _fixCoordSystemInv((instance_mat*p->m_pCameraViewport->GetCameraTarget())+CVect3(0,-10,0) );
eyes[1] = _fixCoordSystemInv((instance_mat*p->m_pCameraViewport->GetCameraTarget())+CVect3(0,60,0) ); 
 // make vector down
/* eyes[0] = CVect3(-1.474797e+001F, -1.195053e+001F,  5.416779e+000F); // Debug absolute position from WP  Azaroth 1164,58,-10645.83
eyes[1] = CVect3(-1.474797e+001F, -1.195053e+001F, -1.754583e+003F);

This BSP seems to be used for collision purpose only.

An object could have has 2 collision system. The first one is encoded in a simplified Geometry (when MOPY. MaterialID=0xFF) the second one is encoded in T_BSP_NODE. Some object has collision method 1 only, some other uses method 2 only. Some object have both collision systems (some polygons are missing in the BSP but are present in the simplified geometry). how to use these 2 system remains unclear.

For the time being, I check first the simplified geometry, and then if there is no collision, I apply a second pass using the BSP. It is sub-optimum, but it seems to work. Probably there is somewhere a flag telling us with which method we should use for the object.

The code attached seems to work fine for BSP method--peter-pan.

MOBR chunk

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

Example code required to get an actual indicies array from MOBR array:

var bpsIndicies = new Array(mobr.length*3);
for (var i = 0; i < mobr.length; i++) {
    bpsIndicies[i*3 + 0] = movi[3*mobr[i]+0];
    bpsIndicies[i*3 + 1] = movi[3*mobr[i]+1];
    bpsIndicies[i*3 + 2] = movi[3*mobr[i]+2];

Example code to get indicies into MOVT for triangles, referenced from BSP node definition:

for (var triangleInd = node.firstFace; triangleInd<node.firstFace+node.numFaces; triangleInd++) {
    //3 vertices per triangle
    movt[bpsIndicies[3*triangleInd + 0]]
    movt[bpsIndicies[3*triangleInd + 1]]
    movt[bpsIndicies[3*triangleInd + 2]]

MOCV chunk

  • Vertex colors, 4 bytes per vertex (BGRA), for WMO/v17 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 WMO/v17s...

After further inspection, this is it, actual pre-lit vertex colors for WMO/v17s - 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!!!

Yes, 0x2000 (INDOOR) flagged WMO groups use _only_ MOCV for lighting, however this chunk is also used to light outdoor groups as well like lantern glow on buildings, etc. If 0x8 (OUTDOOR) flag is set, you start out with normal world lighting (like with light db params) and then you multiply these vertex colors by the texture color and add it to the world lighting. This makes many models look much better. See the Forsaken buildings in Howling Fjord for an example of some that make use of this a lot for glowing windows and lamps. Relaxok 18:29, 20 March 2013 (UTC)


Prior to being passed to the shaders, MOCV values are manipulated by the CMapObj::FixColorVertexAlpha function in the client. This function performs different manipulations depending on the relationship between the vertex and the MOBA it appears in. It's possible that FixColorVertexAlpha did not always exist, or does not exist in later versions of WoW. It appears to have existed in WotLK, Cata, MoP, and WoD.

In client versions that use FixColorVertexAlpha, without applying the function, certain parts of WMOs are noticeably wrong: fireplaces lack a glowing effect; the red light cast from bellows in blacksmith WMOs is undersaturated; etc.

WMOs with MOHD->flags & 0x08

Only one manipulation takes place:

MOCVs matching vertices in MOGP->batchCounts[1] and MOGP->batchCounts[2] are modified like so:

1. If MOGP.flags & 0x08, replace MOCV->color[a] with 255; else replace MOCV->color[a] with 0

All other WMOs

The following manipulations take place:

MOCVs matching vertices in MOGP->batchCounts[0] (aka unkBatchCount) are modified like so:

1. Subtract MOHD->color[r|g|b]
2. Subtract MOCV->color[r|g|b] * MOCV->color[a]
3. Divide new MOCV->color[r|g|b] values by 2.0

MOCVs matching vertices in MOGP->batchCounts[1] and MOGP->batchCounts[2] are modified like so:

1. Subtract MOHD->color
2. Add (MOCV->color[r|g|b] * MOCV->color[a]) >> 6
3. Divide MOCV->color[r|g|b] values by 2.0
4. If values are >= 0 and  <= 255, keep value as is; else clamp new value to 0, 255.
5. If MOGP.flags & 0x08, replace MOCV->color[a] with 255; else replace MOCV->color[a] with 0

Decompiled code

From build 18179, courtesy of schlumpf

void CMapObjGroup::FixColorVertexAlpha(CMapObjGroup *mapObjGroup)
  int begin_second_fixup = 0;
  if ( mapObjGroup->unkBatchCount )
    begin_second_fixup = *((unsigned __int16 *)&mapObjGroup->moba[(unsigned __int16)mapObjGroup->unkBatchCount] - 2) + 1;

  if ( mapObjGroup->m_mapObj->mohd->flags & flag_has_some_outdoor_group )
    for (int i (begin_second_fixup); i < mapObjGroup->mocv_count; ++i)
      mapObjGroup->mocv[i].w = mapObjGroup->m_groupFlags & SMOGroup::EXTERIOR ? 0xFF : 0x00;
    if ( mapObjGroup->m_mapObj->mohd->flags & flag_skip_base_color )
      v35 = 0;
      v36 = 0;
      v37 = 0;
      v35 = (mapObjGroup->m_mapObj->mohd.color >> 0) & 0xff;
      v37 = (mapObjGroup->m_mapObj->mohd.color >> 8) & 0xff;
      v36 = (mapObjGroup->m_mapObj->mohd.color >> 16) & 0xff;

    for (int mocv_index (0); mocv_index < begin_second_fixup; ++mocv_index)
      mapObjGroup->mocv[mocv_index].x -= v36;
      mapObjGroup->mocv[mocv_index].y -= v37;
      mapObjGroup->mocv[mocv_index].z -= v35;

      v38 = mapObjGroup->mocv[mocv_index].w / 255.0f;

      v11 = mapObjGroup->mocv[mocv_index].x - v38 * mapObjGroup->mocv[mocv_index].x;
      assert (v11 > -0.5f);
      assert (v11 < 255.5f);
      mapObjGroup->mocv[mocv_index].x = v11 / 2;
      v13 = mapObjGroup->mocv[mocv_index].y - v38 * mapObjGroup->mocv[mocv_index].y;
      assert (v13 > -0.5f);
      assert (v13 < 255.5f);
      mapObjGroup->mocv[mocv_index].y = v13 / 2;
      v14 = mapObjGroup->mocv[mocv_index].z - v38 * mapObjGroup->mocv[mocv_index].z;
      assert (v14 > -0.5f);
      assert (v14 < 255.5f);
      mapObjGroup->mocv[mocv_index++].z = v14 / 2;

    for (int i (begin_second_fixup); i < mapObjGroup->mocv_count; ++i)
      v19 = (mapObjGroup->mocv[i].x * mapObjGroup->mocv[i].w) / 64 + mapObjGroup->mocv[i].x - v36;
      mapObjGroup->mocv[i].x = std::min (255, std::max (v19 / 2, 0));

      v30 = (mapObjGroup->mocv[i].y * mapObjGroup->mocv[i].w) / 64 + mapObjGroup->mocv[i].y - v37;
      mapObjGroup->mocv[i].y = std::min (255, std::max (v30 / 2, 0));

      v33 = (mapObjGroup->mocv[i].w * mapObjGroup->mocv[i].z) / 64 + mapObjGroup->mocv[i].z - v35;
      mapObjGroup->mocv[i].z = std::min (255, std::max (v33 / 2, 0));

      mapObjGroup->mocv[i].w = mapObjGroup->m_groupFlags & SMOGroup::EXTERIOR ? 0xFF : 0x00;


Similar to FixColorVertexAlpha above, the client will also run MOCV values through the CMapObj::AttenTransVerts function prior to rendering.

In MoP and WoD, it appears that the client only runs AttenTransVerts in cases where flag 0x01 is NOT set on MOHD.flags.

AttenTransVerts only modifies MOCV values for vertices in MOGP.batchCounts[0] (aka unkBatchCount) batches.

The function iterates over all vertices in MOGP.batchCounts[0], and checks all portals for the group:

  • If no portals are found that lead to a group with MOGI.flags & (0x08 | 0x40), all MOCV alpha values are set to 0.0.
  • If a portal is found leading to a group with MOGI.flags & (0x08 | 0x40), each MOCV alpha is manipulated to be a range of 0.0 to 1.0 based on the distance of the corresponding vertex to the portal. Additionally, the RGB values for each MOCV are bumped by: (0.0 to 1.0) * (127 - existingRGB)

Decompiled code

void CMapObj::AttenTransVerts (CMapObj *mapObj, CMapObjGroup *mapObjGroup)
  mapObjGroup->field_98 |= 1u;
  if (!mapObjGroup->unkBatchCount)

  for ( std::size_t vertex_index (0)
      ; vertex_index < (*((unsigned __int16 *)&mapObjGroup->moba[(unsigned __int16)mapObjGroup->unkBatchCount] - 2) + 1)
      ; ++vertex_index
    float opacity_accum (0.0);

    for ( std::size_t portal_ref_index (mapObjGroup->mogp->mopr_index)
        ; portal_ref_index < (mapObjGroup->mogp->mopr_index + mapObjGroup->mogp->mopr_count)
        ; ++portal_ref_index
      SMOPortalRef const& portalRef (mapObj->mopr[portal_ref_index]);
      SMOPortal const& portal (mapObj->mopt[portalRef.portalIndex]);
      C3Vector const& vertex (&mapObjGroup->movt[vertex_index]);

      float const portal_to_vertex (distance (portal.plane, vertex));

      C3Vector vertex_to_use (vertex);

      if (portal_to_vertex > 0.001 || portal_to_vertex < -0.001)
        C3Ray ray ( C3Ray::FromStartEnd
                      ( vertex
                      , vertex
                      + (portal_to_vertex > 0 ? -1 : 1) * portal.plane.normal
                      , 0
          (ray, &portal.plane, 0LL, &vertex_to_use, 0.0099999998);

      float distance_to_use;

      if ( NTempest::Intersect ( vertex_to_use
                               , &mapObj->mopv[portal.base_index]
                               , portal.index_count
                               , C3Vector::MajorAxis (portal.plane.normal)
        distance_to_use = portalRef.side * distance (portal.plane, vertex);
        distance_to_use = NTempest::DistanceFromPolygonEdge
          (vertex, &mapObj->mopv[portal.base_index], portal.index_count);

      if (mapObj->mogi[portalRef.group_index].flags & 0x48)
        float v25 (distance_to_use >= 0.0 ? distance_to_use / 6.0f : 0.0f);
        if ((1.0 - v25) > 0.001)
          opacity_accum += 1.0 - v25;
      else if (distance_to_use > -1.0)
        opacity_accum = 0.0;
        if (distance_to_use < 1.0)

    float const opacity ( opacity_accum > 0.001
                        ? std::min (1.0f, opacity_accum)
                        : 0.0f

    //! \note all assignments asserted to be > -0.5 && < 255.5f
    CArgb& color (mapObjGroup->mocv[vertex_index]);
    color.r = ((127.0f - color.r) * opacity) + color.r;
    color.g = ((127.0f - color.g) * opacity) + color.g;
    color.b = ((127.0f - color.b) * opacity) + color.b;
    color.a = opacity * 255.0;

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 for X and Y
0x1C 	uint16 			material ID

After the header, verts and tiles follow:

struct SMOLVert
    struct SMOWVert
      uint8_t flow1;
      uint8_t flow2;
      uint8_t flow1Pct;
      uint8_t filler;
      float height;
    }  waterVert;
    struct SMOMVert
      int16_t s;
      int16_t t;
      float height;
    } magmaVert;
} verts[xverts*yverts];

struct SMOLTile
  uint8_t liquid : 6;
  uint8_t fishable : 1;
  uint8_t shared : 1;
} tiles[xtiles*ytiles];

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).

Note that although I could read Mh2o's heightmap and existstable in row major order (like reading a book), I had to read this one in column major order to compensate for a 90° misrotation. --Bananenbrot 22:02, 1 August 2012 (UTC)

Either the unknown data or the "types" must somehow control how the points at the edges work. In looking at 3D mesh screen captures, something is changed to create a flat edge where it meets other MLIQ chunks. The first Unknown data is always 0 when a point isn't used. Other seen values: 1, 4, 12, 22, 27, 31, 105, & 124. Not yet sure what they mean/how to use them, I suspect they become the modifier for the edge placement points. --Kjasi 14 February 2016

how to determine LiquidTypeRec to use

enum liquid_basic_types
  liquid_basic_types_water = 0,
  liquid_basic_types_ocean = 1,
  liquid_basic_types_magma = 2,
  liquid_basic_types_slime = 3,

  liquid_basic_types_MASK = 3,
enum liquid_types
  // ...
  LIQUID_WMO_Water = 13,
  LIQUID_WMO_Ocean = 14,
  LIQUID_Green_Lava = 15,
  LIQUID_WMO_Magma = 19,
  LIQUID_WMO_Slime = 20,


  // ...

enum SMOGroup::flags
  is_not_water_but_ocean = 0x80000,

liquid_types to_wmo_liquid (int x)
  liquid_basic_types const basic (x & liquid_basic_types_MASK);
  switch (basic)
  case liquid_basic_types_water:
    return (smoGroup->flags & is_not_water_but_ocean) ? LIQUID_WMO_Ocean : LIQUID_WMO_Water;
  case liquid_basic_types_ocean:
    return LIQUID_WMO_Ocean;
  case liquid_basic_types_magma:
    return LIQUID_WMO_Magma;
  case liquid_basic_types_slime:
    return LIQUID_WMO_Slime;

if ( mapObj->mohd_data->field_3C & 4 )
  if ( smoGroup->field_34 < LIQUID_FIRST_NONBASIC_LIQUID_TYPE )
    this->liquid_type = to_wmo_liquid (smoGroup->field_34 - 1);
    this->liquid_type = smoGroup->field_34;
  if ( smoGroup->field_34 == LIQUID_Green_Lava )
    this->liquid_type = 0;
    int const liquidType (smoGroup->field_34 + 1);
    int const tmp (smoGroup->field_34);
    if ( smoGroup->field_34 < LIQUID_END_BASIC_LIQUIDS )
      this->liquid_type = to_wmo_liquid (smoGroup->field_34);
      this->liquid_type = smoGroup->field_34 + 1;
    assert (!liquidType || !(smoGroup->flags & SMOGroup::LIQUIDSURFACE));


uint16_t triangle_strip_indices[];


  • ignored if !CMap::enableTriangleStrips
  • modifies MOBA, therefore has same count.
  • size is not checked, but 2 * sizeof(int), even though it is only (int, short).
struct MORB_entry
  uint32_t start_index;
  uint16_t index_count;
  uint16_t padding;
  • overwrites 0xC and 0x10 of MOBA (start, count).


  • Map Object Tangent Array
struct MOTA
  unsigned short first_index[moba_count]; // either -1 or first index of batch.count indices into tangents[]. 
                                          // if auto-generated, only has entries for batches with 
                                          // material[batch.material].shader == 10 or 14.
  C4Vector tangents[accumulated_num_indices]; // sum (batches[i].count | material[batches[i].material].shader == 10 or 14)

Is auto generated, if there are batches with shaders 10 or 14, but no tangents. (And maybe some additional condition.) See CMapObjGroup::Create().


struct {
  char unk[0x18];
} map_object_shadow_batches[];


  • likely new in WoD, unknown contents.
  CArgb replacement_for_header_color; // if -1 or not present, take color from header
} mdal;

MOPL (WoD(?)+)

  • requires MOGP.canCutTerrain
C4Plane terrain_cutting_planes[<=32];

MOPB (Legion(?)+)

struct {
  char _1[0x18];
} map_object_prepass_batches[];

MOLS (Legion(?)+)

struct {
  char _1[0x38];
} map_object_spot_lights[];

MOLP (Legion(?)+)

struct {
  char _1[0x2C];
} map_object_point_lights[];