P3D Named Selections

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Named Selections are contained in the Taggs structure in MLOD file format. Every Tagg-name that doesn't have the form #Name# is a named selection. The name of the selection is simply the Tagg-name.

   ulong      NoOfBytes;            //eg. Will always be lod.NoOfPoints + lod.NoOfFaces
   byte       SelectedWeightedPoints[NoOfPoints];
   byte       SelectedFaces[NoOfFaces];

The weights are 'compressed' floating point values; the following functions may be used to encode/decode those values. The conversion functions were found by experimenting and are not guaranteed to yield the correct results.

NB: The byte array's indicate a zero-based offset into the corresponding Points & Faces structures.

To clarify, the purpose of this 'chunk' is to denote which points & faces belong to a given 'Named Selection' and also to denote the 'per-point-weight' associated with this selection.

Each byte in the SelectedWeightedPoints array denotes a value 0 to 255 (0 to FF hex).

And, serves a dual purpose in...

1. Denoting the selectedness and
2. Denoting per point weighting.

  • Zero (0) or 0x00 hex indicates the corresponding point in the LODs Points array is not selected.
Any value other than zero indicates that the point is not only part of the selection but also has a weighting value.

  • One (1) or 0x01 hex indicates the corresponding point in the LODs Points array is selected and has 100% weighting.
Every value between 2 and 255 (0x02 to 0xFF hex) indicates the percentage weight of the corresponding point and that it is part of the selection.
Two (2) being almost 100% weighted and 255 being almost 0% weighted.

float32 byte2weight = (256 - weight)/255; if (byte2weight > 1.0) then byte2weight = 0;

Where 'weight' is a unit8 (single byte) in the range... 0 >= weight <= 255 or 0x00 >= weight <= 0xFF.

 float decodeWeight( uint8 b )
   if( b == 0 ) return  0.0f;
   else if( b == 2 ) return 1.0f;
   else if( b > 2 ) return 1.0f - round( (b-2) / 2.55555f )*0.01f;
   else if( b < 0 ) return -round( b / 2.55555f ) * 0.01f;
   else assert(false); // b == 1 does not occur?

unit8 weight2byte = round(256 - (255 x weight),0); if (weight2byte == 256) then weight2byte = 0;

Where 'weight' is a float32 in the range... 0.0 >= weight <= 1.0.

 uint8 encodeWeight( float f )
   // assume clamped value from 0.0 to 1.0
   if( f < 0.01 ) return 0;
   else if( f > 0.99 ) return 2;
   else if( f > 0.5 ) return 0xff & (int)floor((1.0f - f) * 255.55f + 2);
   else if( f > 0.49 ) return -127;
   else return 0xff & (int)floor(f*2.5555f);


All arrays are subject to the 1024 rule. Which type of compression depends on odol version

  • ODOL7 and ODOL40: LZSS compressed
  • Arma2: LZO compressed.
   asciiz      SelectedName;                       // "rightleg" or "neck" eg
   ulong       NoOfFaces;
   ushort      FaceIndexes[NoOfFaces];             // indexing into the LodFaces Table
   ulong       Always0Count;
   unknownType Array[Always0Count]                 //IsSectional must be true
   ///// ODOL7 only ///////////////////
   ulong       Count;
   ulong       UnknownV7Array[Count];
   tbool       IsSectional;                       //Appears in the sections[]= list of a model.cfg
   ulong       NoOfUlongs;
   ulong       SectionIndex[NoOfUlongs];          //IsSectional must be true. Indexes into the LodSections Table
   ulong       nVertices;
   ushort      VertexTableIndexes[nVertices];
   ulong       nTextureWeights;
   byte        VerticesWeights[nTextureWeights];  // if present they correspond to (are exentsions of) the VertexTableIndexes