Archives & containers

1The install

Steam app 374320, build 10167187. Everything sits in the install's Game/ folder:

fdp is DS3's internal project name. It prefixes the sound banks, the videos and many file names.

2The sealed archives (BHD5)

3Binders inside binders

Almost nothing in the archives is a single asset. Each is a container of containers:

DataN.bdt
 └─ c0000.anibnd.dcx         DCX: a compressed wrapper ("DFLT" = zlib)
     └─ BND4 binder           names and ids for each entry, one file
         ├─ Skeleton.HKX      a Havok 2014 packfile
         ├─ a000_000000.hkx   one spline-compressed animation each …
         └─ c0000.tae         the animation events
map/m40_00_00_00/h40_00_00_00.hkxbhd + .hkxbdt
     └─ BXF4                  the same, split: header (.bhd) and data (.bdt) files

The extension says what a binder holds. We wrote a Python reader for each of these formats, apart from the Lua scripts, which the community's DSLuaDecompiler turns back into source. The ones this codex meets:

4The regulation: every rule as a table

Most of DS3's design numbers aren't in code. They're in params: typed tables of rows, each a fixed struct. The whole set ships as the regulation, Data0.bdt. It is AES-256-CBC encrypted with a fixed key, then DCX-compressed, then a BND4 of 103 .param files data. The save file carries a copy too.

A param file has rows (an id and an offset each) pointing at fixed-size structs. The layouts aren't in the file. Field names and types come from the community's definitions (Smithbox's DS3 defs, Paramdex's row names), which our param reader uses. DS3's files have format byte 0x2D = 0x85: the type name at an offset, and 64-bit row headers.

The params this codex relies on, and what they decide:

5Our side: one importer, neutral formats

The engine never sees a DS3 file. The unpacker extracts what's needed, the readers parse it, and the importer writes flat little-endian files that the engine uses in place after one read. Each has a header (a four-character magic and a version), arrays aligned to 16 bytes, one string table, and right-handed Y-up space in metres. When a format changes, its version goes up and the importer runs again: there are no compatibility layers.

Handedness. DS3 is left-handed, Y up, in metres. The importer negates Z on every position, normal and tangent, and that alone makes the winding counter-clockwise (it agrees with the vertex normals on 99.4 % of a map piece's triangles). Quaternions become (−x, −y, z, w) and root yaw is negated. A play-camera screenshot compared with the real game settled which side is which data.