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
{
CompressedStructs VerticesStruct[...];
float Unkown[12]; // contains some max/min vertices positions
CompressedStructs TexturesStruct[...];
CompressedStructs TableStruct[...];
CompressedStructs FacesStruct[...];
CompressedStruct UnknownStructOne[...];
CompressedStructs NamedStruct[...];
CompressedStruct UnknownStructTwo[...];
CompressedStruct ProxiStruct[...];
};
VerticesStructs
VerticesStructs
{
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
}
ulong Count; // again same value
float Position[Count][3]; // XZY
ulong Count; // again same value
float Normals[Count][3]; // XZY
}
The Position and Normals tables appear to be always uncompressed raw data.
TexturesStruct
CompressedStruct Textures
{
ulong Count;
asciiz Textures[...]; // "data/1.paa\0data/2.paa\0"...
}
Note: the Count corresponds to the number of concatenated asciiz strings. However, it's primary use is to determine whether this is a compressed array or not Since the count * sizeof(byte) is unlikely to ever exceed 1023 ! compression is not a factor. The structure however, is endemic to the way the engine decodes these blocks.
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] ];
UnknownStructOne
CompressedStruct
{
ulong Count;
byte Unknown[Count][18];
}
NamedStruct
NamedStruct
{
CompressedStruct Selection
{
ulong Count;
struct NamedSelection[Count];
}
CompressedStruct Properties
{
ulong Count;
struct NamedPropeties[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];
}
};
NamedPropeties
struct NamedPropeties
{
asciiz Name; // "noshadow\0"
asciiz Value; //"1\0"'
};
UnknownStructTwo
CompressedStruct
{
ulong Count;
struct Unknown
{
ulong Unknown;
CompressedStruct
{
ulong Count;
byte Unknown[Count][12] // unknown value :-( i know nothing about it
}
}[Count];
}
ProxiStruct
CompressedStruct
{
ulong Count;
struct Proxi
{
asciiz Name;
float rotationMatrix[9];
float translation[3];
}[Count];;
}
FacesStruct
struct Faces
{
ulong FacesCount;
ulong unknown;
FaceStruct[FacesCount];
}
FaceStruct
struct Face
{
ulong Attribs;
short TextureIndex;
byte Count; // always 3 or 4
ushort VerticesIndex[4];
};
The TextureIndex is a zero based array. If set to -1, there are no textures for this face.
There are *always* 4 ushort indices allocated. Either 3, or 4 are used.
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
}