DO/BTB

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Contents

Overview

A BTB file (originally thought to be an abbreviation of "Battle Boundaries") contains information about zones, obstacles, objectives and game elements in a Dark Omen map.

The file format is fully binary, and consists of blocks ("chunks") that contains items. Usually the items are atomic (contains a single datum) but sometimes they are records with items in themselves. All blocks and items share the same anatomy and have a 8-byte header (the first 4 bytes is the block type ID, the second is the size of the block, excluding header for top-level blocks ("chunks") but including the header size for items. This is for convievable faster parsing: if you want a particular block you read headers and then chomp size bytes for the next block, while it is probably a Good Think to have the size of items in the full. More likely, however, is that the DO designers thrived on inconsistency.

Tabulation of Blocks and Records

id alias here size notes
0xBEAFEED0 BT_startend 0 No content, just used to indicate file start and end
1 BT_mapdata 240 Fixed content
2 BT_objectives varies Varying contents
3 BT_obstacles varies Varying contents
4 BT_region varies Varying contents
5 BT_gameobjects varies Varying contents
501 IT_obstacle 80 (+header) Sub-block under BT_obstacle, fixed content
503 IT_gameobject 104 (+header) Sub-block under BT_gameobjects, fixed content

Note again that the size values of blocks BT_startend--BT_gameobjects are given exclusive of the header 8 bytes, while the size given in the records IT_obstacle--IT_gameobject are including the 8-byte header.

Tabulation of Data Items

id size what used where used for default data
1 12 integer BT_mapdata, BT_obstacles, IT_gameobject width, x-pos
2 12 integer BT_mapdata, BT_obstacles, IT_gameobject height, y-pos
3 20 3-tuple BT_objectives ???
4 12 integer BT_obstacles ??? depth, z-pos
5 12 integer BT_obstacles, BT_region, IT_gameobject type (flags)
6 12 integer BT_obstacles, IT_gameobject radius
7 12 integer BT_obstacles, IT_gameobject ??? direction usually 0
8 12 integer BT_gameobject # sub-blocks
9 16 2-tuple BT_mapdata regions metadata
10 16 2-tuple BT_region start position
11 16 integer IT_gameobject ??? node ID
12 16 integer IT_gameobject unit ID
13 16 integer IT_gameobject ??? script ID
501 80 sub-block BT_obstacles obstacle data
502 24 4-tuple BT_region line segment
503 104 sub-block BT_gameobject game object data
1001 40 string BT_mapdata merc army file name (w/o ext)
1002 40 string BT_mapdata enemy army file name (w/o ext)

Note that the size member of all data items include the 8-byte header. Thus, a 12-byte integer item consists of 8 bytes of header and four bytes of data.

Linear Layout and Building Blocks

The BTB file consists of chunks of the form: 

struct CHUNK_HEADER
{
  unsigned int chunkType;
  unsigned int chunkSize; // excluding header
};

Each chunk consists of 'records' which are similar to chunks, but the record size is inclusive of the header. 

struct RECORD_HEADER
{
  unsigned int recordType;
  unsigned int recordSize; // including header
};

When coordinates are referenced in the BTB file, divide them by eight to get into the same coordinates as the terrain mesh.

Overall File Structure

The observed format of the BTB files in Dark Omen follows in order: 

START/END CHUNK, type=0xBEAFEED0, size=0

HEADER CHUNK, type=1, size=240
UNKNOWN CHUNK, type=2, size=<varies>
OBSTACLES CHUNK, type=3, size=<varies>
   
REGION CHUNK 0, type=4, size=<varies>
REGION CHUNK 1, type=4, size=<varies>
.
.
.
REGION CHUNK n, type=4, size=<varies>
   
GAME OBJECT CHUNK, type=5, size=<varies>

START/END CHUNK, type=0xBEAFEED0, size=0

Chunk Descriptions

Start/End Chunk

This chunk is just a marker of the start/end of the file; it contains no data


Header Chunk 

HEADER CHUNK, type=1, size=240
   INTEGER RECORD (Map width) type=1, size=12
   INTEGER RECORD (Map height) type=2, size=12
   STRING RECORD (Mercenary Army file name without extension) type=1001, size=40
   STRING RECORD (Enemy Army file name without extension) type=1002, size=40
   STRING RECORD (CTL filename without extension) type=1003, size=40
   STRING RECORD ("/0") type=1004, size=40
   STRING RECORD ("/0") type=1005, size=40
   2-TUPLE RECORD ( [Number of Regions in file, Number of line segments in all regions] ) type=9, size=16


Objectives Chunk

This chunk is made up of several 3-tuples, which contain information about the objectives for this scenario. 

OBJECTIVES CHUNK, type=2, size=<varies>
   3-TUPLE RECORD 0 (unknown) type=3, size=20
   3-TUPLE RECORD 1 (unknown) type=3, size=20 
   .
   .
   .
   3-TUPLE RECORD n (unknown) type=3, size=20

Each tuple is interpreted as: 

(Objective Code, data1, data2)

In SotHR, the objective code is a letter from A-Z, I haven't seen an Objective Code that is greater than 26, so it seems like this may carry over.

Objective
Code 		Description Data 1 Data 2 Effect
C Defines Critical Unit Lose Condition Unique unit ID of critical unit Unknown ex (C, 1, 0) states that Morgan Bernhardt (unit id 1) must not die.


Obstacles Chunk

This chunk seems to contain information about obstacles on the map (e.g. trees). Increase the Integer Record by a higher value (e.g. +10) to avoid crashes in non-official Multiplayer maps. This might imply that the number (type=8) corresponds to an amount of memory to allocate for something. 

OBSTACLES CHUNK, type=3, size=<varies>
   INTEGER RECORD (unknown) type=8, size=12

   COMPOUND RECORD 0 (contains sub-records) type=501, size=80
      INTEGER RECORD (type of obstacle - might be bit flags - see table below) type=5, size=12
      INTEGER RECORD (x position) type=1, size=12
      INTEGER RECORD (y position) type=2, size=12
      INTEGER RECORD (z position) type=4, size=12
      INTEGER RECORD (radius of bounding sphere) type=6, size=12
      INTEGER RECORD (direction - normally 0) type=7, size=12
   COMPOUND RECORD 1 (contains sub-records) type=501, size=80
   .
   .
   .
   COMPOUND RECORD n (contains sub-records) type=501, size=80
Type Description
1 This obstacle is active
2 This obstacle blocks movement into its area
4 This obstacle blocks movement and projectiles into its area

n.b. some of the above information is guessed by analogy to the text script files found in SotHR


Region Chunk

This chunk contains information which delimits an area or path. It primarily consists of a list of line segments which define the path or polygon. These areas and paths seem to be used for a variety of reasons, some of which are listed below. 

REGION CHUNK, type=4, size=<varies>
   STRING RECORD (the human-readable name of the region) type=1006, size=40
   INTEGER RECORD (type code - might be bit flags - see table below) type=5, size=12
   2-TUPLE RECORD ([starting X position, starting Y position]) type=10, size=16
   4-TUPLE RECORD 0 ([ line start X, line start Y, line end X, line end Y]) type=502, size=24
   4-TUPLE RECORD 1 ([ line start X, line start Y, line end X, line end Y]) type=502, size=24
   .
   .
   .
   4-TUPLE RECORD n ([ line start X, line start Y, line end X, line end Y]) type=502, size=24


Bit Value Description
0 1 Always seems to be set
1 2 Closed areas have this bit set
2 4 Paths have this bit set
3 8 Unknown at this time
4 16 About half of the movement boundaries have this bit set
5 32 The Battle Region has this bit set
6 64 Unknown at this time
7 128 The other half of the movement boundaries have this bit set
8 256 Player 1 deployment area has this bit set
9 512 Player 2 deployment area has this bit set
10 1024 The Visible Region has this bit set


Game Objects Chunk

This chunk seems to hold a lot of the game-related info, for example initial enemy deployment, triggers for mission events, movement targets for the enemy AI. 

GAME OBJECTS CHUNK, type=5, size=<varies>
   INTEGER RECORD (the number of game object compound records in this chunk) type=8, size=12

   COMPOUND RECORD 0 (contains sub-records and represents a game object) type=503, size=104
      INTEGER RECORD (type of game object - might be bit flags - see table below) type=5, size=12
      INTEGER RECORD (x position) type=1, size=12
      INTEGER RECORD (y position) type=2, size=12
      INTEGER RECORD (radius of area) type=6, size=12
      INTEGER RECORD (direction) type=7, size=12
      INTEGER RECORD (Script ID?) type=11, size=12
      INTEGER RECORD (Unit ID) type=12, size=12
      INTEGER RECORD (Node ID?) type=13, size=12
   COMPOUND RECORD 1 (contains sub-records and represents a game object) type=503, size=104
   .
   .
   .
   COMPOUND RECORD n (contains sub-records and represents a game object) type=503, size=104

Questions

1) What does the "direction" value say? There is a orientation value in PRJ->TERR for each graphical instance, but what extra information does BTB->ITEM->direction bring?

Well, it seems to me that quite often it will not be used, but for the initial positions of troops etc. the orientation is probably relevant Rob 14:01, 1 January 2009 (UTC)

2) Is the Z position also multiplied by 8 by default?

3) Not having the SotHR data files on my computer, the A--Z interpretation sounds plausible. If we assume that the basic framework from SotHR is carried over do DO (SotHR in fact has more varied mission types than DO, so it is unlikely that DO has extended the SotHR objectives model), do we have the SotHR objectives in more-or-less plaintext?

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