P3D File Format - ODOLV7

Overall

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

Note that potentically 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
{
        VerticesStruct[...];

 float  fvalue[12];              // unknown: contains some max/min vertices positions

 ulong  TexturesCount;
 Asciiz Textures[TexturesCount]; // "data/1.paa\0data/2.paa\0"...

        TableStruct[...];

 ulong  FacesCount;
 ulong  uvalue;                  // unknown
 struct Face[FacesCount];
 
 ulong  uvalue2;                 // unknown
 byte   uchar[18*uvalue2];       // unknown valuea
 
        NamedStruct[...];
 
 ulong uvalue7;                 // unknown value ???
 struct ustruct[uvalue7];       // unknown value
 
 ulong ProxiCount;
 struct Proxi[ProxiCount];
}; // end of lod

VerticesStruct

 VerticesStruct
 { 
   CompressedStruct Attribs
   {
    ulong Count;
    ulong Attribs[Count];     // if > 255 then array is compressed 
   }
   CompressedStruct UVset
   {
    ulong Count;              // again same value
    float UVset[Count];       // if > 127 then array is compressed 
   }
   CompressedStruct Position
   {
    ulong Count;              // again same value
    float Position[Count][3]; // XZY.  If > etc
   }
   CompressedStruct Normals
   {
    ulong Count;              // again same value
    float Normals[Count][3];  // XZY. If > etc
   }
 }

TableStruct

struct TableStruct
{
 CompressedStruct Table1
 {
  ulong  Count;
  ushort Table1[Count];// if > 511 array compressed   
 }
 CompressedStruct Table2
 {
  ulong  Count;        // this Count is same value as any Vertices.Count
  ushort Table2[Count];// > 511 then array is compressed 
 }
}

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 = Table1[ Table2[ODOLvertexindex] ];

NamedStruct

NamedStruct
{
 CompressedStruct Selection
 {
  ulong  Count;
  struct Selection[Count];
 }
 CompressedStruct Properties
 {
  ulong  Count;
  struct Propeties[Count]
 }
}

CompressedStruct

a compressed struct is such that if the Count * sizeof data type is > 1023 then lzh compression is used

Thus,

• ulong arrays = > 255
• float[2] = > 127
• etc

Faces

  struct Face
    {
      uint Attribs;
      word TextureIndex; //if ((int)TextureIndex==-1) no texture;
      char CountOfVertices;  // 3 or 4
      word VerticesIndex[CountOfVertices]; //! size of array is not constant.
    };

NamedSelection

  struct NamedSelection
    {
      char name[...]; // zero ended string
 
      uint VerticesSelectedCount;
      word VerticesSelected[VerticesSelectedCount];// if VerticesSelectedCount > 511 then array is compresed by LZ algorithm. see LZ in ODOL.
 
      uint uvalue3; // unknown value
      word uarray[uvalue3];// unknown value
 
      uint uvalue4; // unknown value
      uint uarray[uvalue4];// unknown value // if VerticesSelectedCount > 255 then array is compresed by LZ algorithm. see LZ in ODOL.
 
      char uchar; // unknown value 
  
      uint uvalue5; // unknown value
      uint uarray[uvalue5];// unknown value
 
      uint FacesSelectedCount;
      word FacessSelected[FacesSelectedCount]// if FacesSelectedCount > 511 then array is compresed by LZ algorithm. see LZ in ODOL.
 
      uint uvalue6; // unknown value
      char uarray[uvalue6];// unknown value
    };

Proxi

  struct Proxi
    {
      char Name[...] // zero ended  string
      float rotationMatrix[9];
      float translation[3];
    };

ustruct

  struct ustruct // unknown value
    {
      uint uvalue8;// unknown value
      uint uvalue9;// unknown value
      char uarray[12*uvalue9];// unknown value :-( i know nothing about it
    };

NamedPropeties

  struct NamedPropeties
    {
      char Name[...];
      char Value[...]; // 'n','o','s','h','a','d','o','w','\0','1','\0'...
    };

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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