P3D File Format - MLOD

Acknowledgments

This information comes largely from the long defunct 'ofpinternals', who in turn acknowledge

Thanks to FlipeR (filipus@hotmail.com) for helping in research

This is archive material is held at http:\\www.ofpec.com

Legend

see Generic FileFormat Data Types

Introduction

Any given P3D file is THE 3 dimensional model reference for a specific model. Tank, Man, House, sausage. The P3d contains references to pac/paa files which are individual 'surfaces' for *this* model. Some / Most / All of the pac/paa files *might* also be used in other models, but this p3d is THE T80 tank, THE civilian man, or THE tangerine sausage with pink spots.

Arma P3D files also contain references to materials (rvmats).

There are two basic P3D types

• ODOL: A binarised and compressed version as used by various engines. (OFP, ARMA eg)
• MLOD: An editable version as used by Oxygen2/3 eg.

The FILE header defines which, of the two types, this P3D is.

This document describes MLOD P3D's

Every LOD in an MLOD containts a LOD Header which defines the type of lod as being

• SP3X used in OFP: Uses O2Light for editing
• P3DM used in ARMA:Uses O2PE for editing

Arma can read EITHER.

Because each of the contiguous lods declares what 'type' it is (SP3X, or P3DM), architecturally, you could have mixtures of both types. Materials however, can only be defined by P3DM lods.

Although the overall structure of a P3DM mlod model file is similar to SP3X mlod model files there are some notable differences. Namely, Materials, Multiple UVSets and Animations.

---

File Format

MLOD_P3D
{
  P3DHeader P3DHeader;
  MLOD_LOD  MLOD_LODs[Header.NoOfLods];
  char      SP3X_DefaultPath[32]; // optional OFP only
}

• SP3X Lods contain a rarely encountered, optional, Default File path (probably for the editor)

P3DHeader

P3DHeader
{
 char   Signature[4];        //"MLOD"
 ulong  Version;             // 0x101 see note
 ulong  NoOfLods;            // at least one
};

OdolExplorer

OdolExplorer sets the version to a float value of 1.1 with no ill-effect

MLOD_LOD

Struct
{
  char[4]                     Signature;           //"SP3X" or "P3DM"
  ulong                       MajorVersion;        //28 (x1C)
  ulong                       MinorVersion;        //0x99 (SP3X) or 0x100 (P3DM)
  ulong                       NoOfPoints;
  ulong                       NoOfNormals;         //(perpendicular)
  ulong                       NoOfFaces;
  ulong                       UnknownFlagBits;     //Probably 'Model Flags' - Unused.
  Point                       Points[NoOfPoints];
  XYZTriplet                  Normals[NoOfNormals];
  Faces                       Faces[NoOfFaces];    //see P3D Lod Faces
  char                        TagSig;              //Always 'TAGG'
  Tagg[]                      Taggs;               //Always, minimum of #EndOfFile# tag exists.
  float                       Resolution;          //See P3D_Model_Info 
}

The end of each structure *always* contains an #EndOfFile# TAGG followed by the resolution (of that lod)

Points

struct
{
   XYZTriplet    Position
   ulong         PointFlags;// see P3D Point and Face Flags
}

Normals

Normals must be inverted (-X, -Y, -Z) for clockwise vertex order (default for DirectX), and not changed for counterclockwise order.

Taggs

 struct
 {
   //////// P3DM ONLY ///////////
   TinyBool Active;            // always 1
   Asciiz   TaggName;          // "#EndOfFile#\0" eg
   ///////  SP3X ONLY ///////////
   Asciiz   TaggName[64];      // "#EndOfFile#\0" eg
   //////////////////////////////
   ulong    NoOfBytes;         // offset to next tagg
   byte     TaggData[NoOfBytes];// arbitrary data
 };

TagNames

Every Lod contains one or more Tagname entries. The #EndOfFile# tag is a mandatory entry in every Lod to indicate no more tags! The contiguous tags that make up the tag section are always in the above format. The actual structure of the 'ArbitraryData' is dependant on the TagName.

TaggNames consist of a mixure of pre-defined Taggs indicated with #.....# marks, and 'Named Selections'

Named Selection tagg names can contain Proxy names beginning with 'proxy:' + ProxyName + '.' + ProxyNumber ('01' ...

• Every Lod has an #EndOfFile# Tagg
• Every Arma Lod has at least one #UVSet# Tagg. The first of which is a duplicate of that found in LodFaces. (ofp has no #UVset# because there is only ever one)
• The #Mass# tag is mandatory for Geometry LODs and only present in Geometry LODs.

Tagg names listed below are a mish mash of obsolete, and still used, commands. This because, the p3d was a still in development at time of CWC release.

#EndOfFile#

ulong   NoOfBytes; //always 0

Mandatory for every Lod. This is the last tag of current LOD. It contains no data.

#SharpEdges#

ulong          NoOfBytes;
ulong          PointsIndex[NoOfIndexes][2]; // NoOfIndexes= NoOfBytes /  2 * sizeof(ulong)..// 1st and 2nd indexes into the VertexTable 

Sharp edge means that these vertices normals are not calculated as average (normalized) between polygons.

#Property#

 ulong                      NoOfBytes;            //Always 128
 Asciiz                     TokenKey[64];         //"lodnoshadow" (=) "1"
 Asciiz                     TokenValue[64];       //

Additional Properties (if any) for the lod are contained in a series of one or more property tags. Each one contains one, and one only Token-Pair. The Asciiz strings each have a fixed length of 64 characters. Regardless, they are null terminated.

Examples:

damage=tree;
CanOcclude=0;

#Mass# (only for Geometry LOD)

ulong          NoOfBytes;
float          PointsMass[NoOfPoints];  // == NoOfBytes / sizeof(float).. same as Lod.NoOfPoints

Must be present for Geometry LOD, and only for Geometry lod. It refers to the mass of each Point entry.

#Animation#

ulong         NoOfBytes;  //==sizeof(float)+Lod.NoOfPoints*sizeof(XYZTriplet)
float         FrameTime;
////////// SP3X ONLY ///////
ulong         NoOfPoints; // Must be the same as the LOD's NoOfPoints. 
/////////////////////////////////
XYZTriplet    FramePoints[NoOfPoints];

There are a contiguous series of #Animations# making up the total. Each one has an identical number of triplets, any of which are same count as the lod's NoOfPoints.

AnyFramePoints.NoOfPoints == AnyOtherFramePoints.NoOfPoints == lod.NoOfPoints

NB: There will be 1 '"#Animation#' chunk per Frame. This can result in VERY large p3dm mlod models. A model with three thousand (3,000) odd frames (eg. ActsPercMstpSnonWnonDnon_DancingStefan.rtm) will be approx. 200 Megabytes on disk.

This type of data format for Animation is commonly known as a 'Point Cache' or an 'MDD Point Cache'. It describes the exact location of every point in the LOD in 3D 'Model Space' for each frame.

#UVSet# ARMA

ulong       NoOfBytes;                   //see below
ulong       ID;
UVPair      FaceUV[NoOfFaces][FaceType]; //see P3D Lod Faces

Introduced for Arma to supply up to 8 distinct #UVset#s per lod.

• There is at least one (and generally only one) #UVSet# for every lod.

This #UVSet# (ID=0) is a redundant duplication of that found in Lodfaces.

There is a slight re-arrangement of the UV array in the UVset vs that found in LodFaces. The amount of data however, is identical. (And in the case of uvset0, the data is identical).

note that 'identical' floating point values are rare because the IEEE represention of any given value is a range of precisions. The value 0.02 eg cannot be represented exactly, as a float (or double for that matter).

The following code compares, in a general sense, two floats for 'identicalness'

bool AlmostEqual(float A, float B)
{
   if (A == B)  return true; // gets over neg and positive zero
   return abs(*(int*)&A - *(int*)&B)==0; // gets around nans' qnans
}

For a very, very good article on this subject http://www.cygnus-software.com/papers/comparingfloats/comparingfloats.htm

A UVpair matches each vertex in every LodFace

LodFaces themselves can have either 3, or 4, UVPairs per index. Thus, the amount of data in this structure varies.

The number of bytes therefore used by this #UVset and every other UVset in this lod is calculated as

sizeof(ulong)+ sizeof(UVPair)* (3*LodFace.NoOfTriangles+4*LodFace.NoOfQuads)

#Hide# (only used in O2)

ulong      NoOfBytes;                  // ==Lod.NoOfPoints + lod.NoOfFaces
TinyBool   PointsIndex[NoOfPoints];    // nonzero = true
TinyBool   FaceIndex[NoOfFaces]; 

These 3 are used so that O2 can save your last selections in the edited file. They serve no other purpose outside of editing the model in O2.

These table correspond to each entry of Points and Faces respectively and indicate whether that Point (or Face) at that index is 'selected/locked/hidden' or not and is a a persisted selection within the P3DM at this time.

The values are supposed to be 0 and 1. This is mostly the case, however, some 'bytes' contain values such as 2 or 6, but also mean, 'true'

#MaterialIndex# (only in O2)

Unknown tag. Used only in O2. Possibly ofp only. This tag contains a 16-byte structure:

Seems, this tag contains material properties:

4 (RGBA or BGRA) diffuse 
4 (RGBA or BGRA) ambient 
4 (RGBA or BGRA) specular 
4 (RGBA or BGRA) emissive 

By default, O2L write down this values:

51, 75, 55, 0 
0, 0, 0, 0 
255, 255, 255, 255 
255, 255, 255, 255