BIFF file format

Applies to:
BG1, BG1: TotS, BG2, BG2: ToB, PST, IWD, IWD:HoW, IWD:TotL, IWD2

File versions
BIF (BG1, IWD1, PST)
BIFC (IWD1)
BIFC 1.0 (BG2)

General Description
This is a simple archive format, used both to simplify organization of the files, as well as to group together entire areas. Some BIF files are grouped together because of common functionality; for instance, all the .dlg files are gathered together into a single BIF file in Planescape: Torment. Other bif files, such as AR4800.BIF represent the entirety of an area's terrain (i.e. not its containers, actors, or items). These BIF files contain, typically:
  • 1+ .wed file, detailing how the tiles are to be drawn to the screen (i.e. which are animated, which are linked to the opening of which door, etc.) and where walls are (for clipping of actor graphics)
  • 1+ .tis file, which contains all the tile data for the area
  • 1 .mos file which is the overhead map of the region
  • 3 or 4 small bitmap files which contain one pixel for each tile needed to cover the region.

    • The three (or four) bitmaps, are named xxxxxxHT.BMP, xxxxxxLM.BMP, xxxxxxSR.BMP, and (when there are four bitmaps) xxxxxxLN.BMP.
  • xxxxxxHT.BMP: Height-map, which gives the altitude of each tile cell in the associated wed file
  • xxxxxxLM.BMP: Light-map, giving the level of illumination (or shadow) of each tile cell on the map. (Called a LUM-map by the developers.)
  • xxxxxxLN.BMP: When present, this is the same as xxxxxxLM.BMP, but for night-time only. When present, there will also be a second wed file to be used only at night.
  • xxxxxxSR.BMP: Search Map. Used for path-finding, and marking map sections as passable/water/etc

    • BIFF V1
    Overall structure:
  • Header
  • File entries
  • Tileset entries
  • Data for the contained files

    • BIFF V1 Header

    Offset Size (data type) Description
    0x0000 4 (char array) Signature ('BIFF')
    0x0004 4 (char array) Version ('V1 ')
    0x0008 4 (dword) Number of file entries
    0x000c 4 (dword) Number of tileset entries
    0x0010 4 (dword) Offset of file entries (from start of file). Tileset entries, if any, immediately follow the file entries.

    BIFF V1 File Entries

    Offset Size (data type) Description
    0x0000 4 (dword) Resource locator
    (NB: On disk, only bits 0-13 are matched upon. They are matched against the file index in the "resource locator" field from the KEY file resource entries which claim to exist in this BIFF.
    0x0004 4 (dword) Offset to resource data from start of file
    0x0008 4 (dword) Size (bytes) of this resource (file).
    0x000c 2 (word) Type of this resource. (See the table of resTypes for a list of which values are applicable to this field
    0x000e 2 (word) Unknown. Part of the previous field? (Or only used in the memory image?)

    BIFF V1 Tileset Entries

    Offset Size (data type) Description
    0x0000 4 (dword) Resource locator
    (NB: On disk, only bits 14-19 are matched upon. They are matched against the tileset index in the "resource locator" field from the KEY file resource entries which claim to exist in this BIFF.
    0x0004 4 (dword) Offset to resource data from start of file
    0x0008 4 (dword) Number of tiles in this resource (file).
    0x000c 4 (dword) Size (bytes) of each tile in this resource (file).
    0x0010 2 (word) Type of this resource. (These resources are always type 0x3eb (TIS files), but see the table of resTypes for a list of which values are applicable to this field
    0x0012 2 (word) Unknown. Part of the previous field? (Or only used in the memory image?)

    BIFC V1 file format
    BIFC V1
    Overall structure:
  • Header
  • Compressed file data
    • This format is identical to the SAV file format, except for the first 8 bytes, which are 'BIF V1.0' for these files, and 'SAV V1.0' for SAV files. The data, once uncompressed, is formatted as a normal BIF file, as seen above. Note that the SAV files can hold more than one compressed file. It is unknown whether this occurs also in CBF files. The compressed format is as follows:

    Header

    Offset Size (data type) Description
    0x0000 4 (char array) Signature ('BIF ')
    0x0004 4 (char array) Version ('V1.0')
    0x0008 4 (dword) Length of filename
    0x000c variable (ASCIIZ char array) Filename (length specified by previous field)
    sizeof(filename)+0x0010 4 (dword) Uncompressed data length
    sizeof(filename)+0x0014 4 (dword) Compressed data length
    sizeof(filename)+0x0018 variable (raw data) Compressed data (length in bytes specified by previous field)

    BIFC V1.0 file format
    BIFC V1.0 (compressed)
    Overall structure:
  • Header
  • zlib-compressed blocks
    • The file is broken up into blocks (typically 8192 bytes apiece), which are compressed separately. The blocks are stored one right after another, immediately after the header. Each block consists of an uncompressed size and a compressed size, and then the data, compressed by zlib.

    Header

    Offset Size (data type) Description
    0x0000 4 (char array) Signature ('BIFC')
    0x0004 4 (char array) Version ('V1.0')
    0x0008 4 (dword) Uncompressed BIF size

    Compressed Blocks

    Offset Size (data type) Description
    0x0000 4 (dword) Decompressed size
    0x0004 4 (dword) Compressed size
    0x0008 varies (bytes) Compressed data