---
name: "P3D Named Selections"
type: topic
source: https://community.bistudio.com/wiki/P3D_Named_Selections
revid: 373434
updated: 2025-05-08T11:27:13Z
---

# P3D Named Selections

> **Disclaimer: This page describes internal undocumented structures of Bohemia Interactive software.**
>
> This page contains unofficial information.
>
> Some usage of this information may constitute a violation of the rights of Bohemia Interactive and is in no way endorsed or recommended by Bohemia Interactive.\
> Bohemia Interactive is not willing to tolerate use of such tools if it contravenes any general licenses granted to end users of this community wiki or BI products.

## Intro

placeholder till better organsied

## MLOD

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);
 }
```

## ODOL

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

- ODOL7 and ODOL40: LZSS compressed
- Arma2: LZO compressed.

```
 LodNamedSelection
 {
   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
 }
```

<sub>Source: [BI Community Wiki — P3D Named Selections](https://community.bistudio.com/wiki/P3D_Named_Selections) (revision 373434).</sub>