P3D File Format - ODOLV7

Legend

byte:     8 bits unsigned
char:     8 bit ascii character
char[]:   fixed length string
asciiz:   null terminated char string
asciiz... concatetaned asciiz strings
asciiz[]: fixed length and null terminated anyway
ulong:    unsigned integer 32bit. 4 bytes
ushort:   unsigned integer 16bit 2 bytes
short:    signed integer 16bit 2 bytes
float:    4 bytes

Intro

CompressedStruct

ODOL7 uses (potentially) compressed arrays.

This obviously slows the engine down during loading. At the time of CWC development, game file sizes were important.

(potentially) compressed arrays are contained in a CompressedStruct

CompressedStructs are endemic to most blocks contained in the p3d.

CompressedStruct
{
  ulong  Count;
  <type> Array[Count];
};

if Count * sizeof(<type>) exceeds 1023 bytes the array is compressed. The resulting array will be expanded using lzh compression exactly as found in pbo's (for instance)

After de-compression, the Count remains the same because it is a count of the arraytype.

For uncompressed arrays (byte count < 1024) the Count and data are treated 'as is'.

Thus for various Array <types>

*ulong Array:    > 255  // 1024 /   sizeof(ulong)
*float thing[2]: > 127  // 1024 / 2*sizeof(float)
*SomeStructure:  >      // count * sizeof (SomeStructure) > 1023

Note that potentially compressed arrays in these structures only have an known output length. the decompressor therefore must work on infinite input length. see example decompression at end of document

Odol7Stuct

ODOLV7
{
  StandardP3DHeader Header;
  LodStruct Lods[LodCount];
  float     Resolution[LodCount];
  ulong     Unknown;         // typically 02 01 00 00
  float     Pair[2];         // typically 48 74 07 3F  : 48 74 07 3F . pair is often the same
  ulong     Unknown[3]       // typically 00 00 00 00 00 00 00 00 00 00 B0 0D 
  bytes     Unknown[120];    // a mixture of floats and index values
  bytes     UnknownFlags[6]; // typically 01 00 00 01 00 16
  ulong     Count;
  float     Array[Count];    // potentially compressed
  float     UnknownFloats[4];// almost consistently 00 00 00 00 : F9 02 15 50 : 00 00 48 43 : 0A D7 A3 3B
  ulong     UnknownLongs[3]; // generally FF FF FF FF FF FF FF FF FF FF FF FF
};

StandardP3DHeader

StandardP3DHeader
{
  char      Signature[4];      //"ODOL"
  ulong     Version;           // 7
  ulong     LodCount;          // at least one
}

LodStruct

LodStruct
{
 structs VerticesStructs[...];

 float   Unknown[12];           // contains some max/min vertices positions

 struct  TexturesStruct[...];
 
 structs TableStructs[...]; 

 struct  FacesStruct[...];

 struct  UnknownStruct[...];

 ulong          nNamedSelections;
 NamedSelection NamedSelections[nNamedSelections];
 ulong          nNamedProperties;
 NamedProperty  NamedProperties[nNamedProperties];

 struct  UnknownStruct2[...];

 ulong   Unknown[3];

 struct  ProxiStruct[...];
};

VerticesStructs

 VerticesStructs
 { 
   CompressedStruct Attribs
   {
    ulong Count;              // if > 255 then array is compressed 
    ulong Attribs[Count];     
   }
   CompressedStruct UVset
   {
    ulong Count;              // if > 127 then array is compressed 
    float UVset[Count];       
   }
   struct Position
   {
    ulong Count;              
    float Position[Count][3]; // XZY
   }
   struct Normals
   {
    ulong Count;             
    float Normals[Count][3];  // XZY
   }
 }

• Count is the same value for all four tables.
• The Position and Normals tables appear to be always uncompressed raw data.

TexturesStruct

 struct Textures
 {
  ulong  Count;
  asciiz Textures[...];          // "data/1.paa\0data/2.paa\0"...
 }

Count corresponds to the number of concatenated strings. It is required, since, architecturally at least, one of more of the asciiz strings could be null.

TableStruct

struct TableStruct
{
 CompressedStruct 
 {
  ulong  Count;            // if > 511 etc  
  ushort MlodIndex[Count];
 }
 CompressedStruct
 {
  ulong  Count;           // this Count is same value as any Vertices.Count
  ushort OdolIndex[Count];// 
 }
}

Tables are used to join vertices. Each face has got 3 or 4 vertices that are unique for each face Eg. Every vertex is owned only by 1 face.

MLODvertexindex = MlodIndex[ OdolIndex[ODOLvertexindex] ];

FacesStruct

struct Faces
{
 ulong  FacesCount;
 ulong  unknown;
 struct Face
 {
  ulong  Attribs;
  short  TextureIndex; 
  byte   Count;  // always 3 or 4
  ushort VerticesIndex[Count];
 }[FacesCount];
};

The TextureIndex is a zero based array. If set to -1, there are no textures for this face.

UnknownStruct

 UnknownStruct
 {
  ulong  Count;
  byte   Unknown[Count][18];
 }

NamedSelection

NamedSelection
{
 asciiz name;
 CompressedStruct Vertices
 {
  ulong  Count;                  // if > 511 then array is compressed
  ushort Vertices[Count];
 }
 CompressedStruct UnknownUshort
 {
  ulong   Count;                 // if > 511 then array is compressed
  ushort  Unknown[Count];
 }
 CompressedStruct UnknownUlong
 {
  ulong Count;                    // if > 255 then array is compressed
  ulong Unknown[Count];
 }
 byte IsSectional; 
 CompressedStruct UnknownUlong2
 {
  ulong Count;                    // if etc
  ulong Unknown[Count];
 }
 CompressedStruct Faces
 {
  ulong Count;                    // if etc
  ushort Faces[Count];
 }
 CompressedStruct TextureWeights      // probably
 {
  ulong Count;                    // if etc
  byte TextureWeights[Count];
 }
};

NamedProperty

 NamedProperty
 {
   asciiz Name;  // "noshadow\0"
   asciiz Value; //"1\0"'
 };

Frame

   Frame
   {
     float FrameTime;
     ulong nBones;
     XYZTriplet [nBones];
   };

ProxiStruct

ProxiStruct
{
 ulong  Count;
 struct Proxi
 {
  asciiz Name;
  float rotationMatrix[9];
  float translation[3];
  ulong Index[2];
 }[Count];;
}

LZ in ODOL

Lempel-Ziv compression

Note1.

Regardless of method, 4 extra bytes representing the checksum exist at end of the data count.

Note2. The compression code is identical to that employed by pbo packed structures. However, unlike pbo's, the size of the compressed data is unknown, only it's ultimate length. The code below fudges it.

pascal code

function LZBlockRead(var F:file; var outdata:array of byte;szout:integer):byte;
var
k, r, pr, pi,po,i,j:integer;
flags:word;
buf:array[0..$100e] of byte;
c:byte;
crc:integer;
begin
po:=0;
pi:=0;
flags:=0;
r:=0;
for k := 0 to $100F-1 do buf[k] := $20;
       while (po < szout) do
        begin
           flags:= flags shr 1;
           if ((flags and $100)= 0) then
               begin
                 BlockRead(F,c,1);   // direct reading from file
                 inc(pi);
                 flags := c or $ff00;
               end;
           if (flags and 1)=1 then
                begin
                  if (po >= szout)then break;
                  BlockRead(F,c,1);   // direct reading from file
                  inc(pi);
                  outdata[po] := c;
                  inc(po);
                  buf[r] := c;
                  inc(r);
                  r :=r and $fff;
                end
           else
                begin
                  i:=0;
                  BlockRead(F,i,1);  // direct reading from file
                  inc(pi);
                  j:=0;
                  BlockRead(F,j,1); // direct reading from file
                  inc(pi);
                  i :=i or ((j and $f0) shl 4);
                  j := (j and $0f) + 2;
                  pr := r;
                  for k := 0 to j do
                    begin
                      c := buf[(pr - i + k) and $fff];
                      if (po >= szout) then break;
                      outdata[po]:= c;
                      inc(po);
                      buf[r]:= c;
                      inc(r);
                      r :=r and $fff;
                    end;
             end;
       end;
     BlockRead(F,crc,4);   // 4 byte checksum.
     result:= pi;
end;

C code

int Decode(unsigned char *in,unsigned char *out,int szin,int szout)
{
       szin = szin > 0? szin: 0x7fffffff;
       int  i, j, k, r = 0, pr, pi = 0,po = 0;
       unsigned int  flags = 0;
       unsigned char buf[0x100F], c;
       for (i = 0; i < 0x100F; buf[i] = 0x20, i++);
       while (pi < szin && po < szout)
       {
               if (((flags >>= 1) & 256) == 0)
               {
                       if(pi >= szin)break;
                       c = in[pi++];
                       flags = c | 0xff00;
               }
               if (flags & 1)
               {
                       if(pi >= szin || po >= szout)break;
                       c = in[pi++];
                       out[po++] = c;
                       buf[r++] = c;
                       r &= 0xfff;
               } else
               {
                       if(pi + 1 >= szin)break;
                       i = in[pi++];
                       j = in[pi++];
                       i |= (j & 0xf0) << 4;
                       j  = (j & 0x0f) + 2;
                       pr = r;
                        for (k = 0; k <= j; k++)
                       {
                               c = buf[(pr - i + k) & 0xfff];
                               if(po >= szout)break;
                               out[po++] = c;
                               buf[r++] = c;
                               r &= 0xfff;
                       }
               }
       }
       return pi;// next 4 bytes = checksum
}

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