P3D File Format - ODOLV7

Overall

// uint unsigned integer 32bit
// word unsigned short integer 16bit
// 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

struct ODOL
  {
  char Signature[4]; //"ODOL"
  uint Version;     // 7
  uint LodCount;    // at least one
  struct Lod[LodCount]
  {
    uint VerticesCount;
    uint VerticesAttribs[VerticesCount]; // if > 255 then array is compresed
 
    uint VerticesCount; // again same value
    struct UVset[VerticesCount]; // if > 127 then array is compresed 
 
    uint VerticesCount; // again same value
    struct VerticesPosition[VerticesCount];
 
    uint VerticesCount; // again same value
    struct VerticesNormal[VerticesCount];
 
    float fvalue[12];  // unknown values // containts some max/min vertices positions and so far
 
    uint TexturesCount;
    char Textures[...]; // zero ended 'C' strings 'd','a','t','a','\','1','.','p','a','a','\0','d','a','t','a','\','2','.','p','a','a','\0'...
    //read until count of founded char('\0') equil TexturesCount;
 
    uint Table1stCount;
    word Table1st[Table1stCount];// if > 511 array compresed   
    uint Table2ndCount; // Table2ndCount is same value like VerticesCount
    word Table2nd[Table2ndCount];// > 511 then array is compresed
    //tables can by used to join vertices, each face has got 3 or 4 vertices that are seperated for each face in odol format
    //every vertex is owned only by 1 face
    //mlodvertexindex = Table1st[ Table2nd[ odolvertexindex ] ];
 
    uint FacesCount;
    uint uvalue;  // unknown value
    struct Face[FacesCount];
 
    uint uvalue2; // unknown value
    char uchar[18*uvalue2]; // unknown value
 
    uint NamedSelectionCount 
    struct NamedSelection[NamedSelectionCount]
 
    uint NamedPropetiesCount;
    struct NamedPropeties[NamedPropetiesCount]
 
    uint uvalue7;// unknown value ???
    struct ustruct[uvalue7]; // unknown value
 
    uint ProxiCount;
    struct Proxi[ProxiCount];
  }; // end of lod
uint ResolutionCount; // same as LODCount
float  Resolution[ResolutionCount];
.
.
. // folows some unknow data.
}; // end of ODOL;

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
    };

VerticesPosition

   struct VerticesPosition
    {
      float x,y,z;
    };

VerticesNormal

   struct VerticesNormal
    {
      float x,y,z;
    };

UVset

   struct UVset
    {
      float U,V;
    };

Proxi

  struct Proxi
    {
      char Name[...] // zero ended  string
      struct ustruct {...};// size same as char[56]; // unknown value
    };

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.

Rregardless 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
}