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

struct ODOL
{
  char      Signature[4];      //"ODOL"
  ulong     Version;           // 7
  ulong     LodCount;          // at least one
  LodStruct Lod[LodCount];
  ulong     ResolutionCount;   // same as LodCount
  float     Resolution[ResolutionCount];
  byte      unknownBytes[24];
  float     offset[3];         // model offset (unknown functionality)
  ulong     mapIconColor;      // RGBA 32 color
  ulong     mapSelectedColor;  // RGBA 32 color
  ulong     unknownValue;
  float     bboxMinPosition[3]; // minimum coordinates of bounding box
  float     bboxMaxPosition[3]; // maximum coordinates of bounding box
  float     wrpModelOffset[3];  // offset value to apply when object is placed on a WRP
  float     offset2[3];         // another offset value (unknown functionality)
};

LodStruct

LodStruct
{
 structs VerticesStructs[...];

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

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

 struct  FacesStruct[...];

 struct  UnknownStruct[...];

 structs NamedStructs[...];
 
 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 and is somewhat redundant.

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];
 }

NamedStruct

NamedStruct
{
 CompressedStruct Selection
 {
  ulong  Count;
  struct NamedSelection[Count];
 }
 struct NamedProperties
 {
  ulong  Count;
  struct 
  {
   asciiz Name;  // "noshadow\0"
   asciiz Value; //"1\0"'
  }Properties[Count];
 }
}

NamedSelection

struct 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 Unknown; 
 CompressedStruct UnknownUlong2
 {
  ulong Count;                    // if etc
  ulong Unknown[Count];
 }
 CompressedStruct Faces
 {
  ulong Count;                    // if etc
  ushort Faces[Count];
 }
 CompressedStruct UnknownByte
 {
  ulong Count;                    // if etc
  byte Unknown[Count];
 }
};

UnknownStruct2

UnknownStruct2
{
   ulong Count;
   struct Unknown
   {
     ulong uvalue8;// unknown value
     ulong Count;
     byte  array[12*Count];// unknown value :-( i know nothing about it
   }[Count];
};

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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Model File Formats