AC6_recomp/docs/ac6_asset_pipeline.md

AC6 Asset Pipeline

This pipeline extracts and converts the AC6 assets we currently understand.

It automates these stages:

1. DATA.TBL + DATA00.PAC / DATA01.PAC index extraction
2. Runtime PAC decode dump parsing
3. Recursive FHM extraction
4. SWG UI metadata parsing
5. NTXR texture export

Offline mode-1 decompression (solved)

The pipeline can now decompress every compressed PAC entry fully offline, with no need to launch the game. The AC6 "mode-1" codec has been reverse-engineered:

1. Descramble: stored bytes are XORed with an 8-byte repeating pad. The pad for a DATA.TBL entry is derived from the entry's table index:

   pad(index) = pi_words[2*(index % 256) + 1] ++ pi_words[2*(index % 256) + 2]
   

   where pi_words are the big-endian base-2^32 words of the fractional part of pi (0x243F6A88 0x85A308D3 0x13198A2E ...). The game generates these at runtime via Machin's formula (4*arctan(1/5) - arctan(1/239)); the offline tool simply computes pi to the needed precision.

2. Inflate: the descrambled bytes are raw DEFLATE (RFC 1951, no zlib/gzip wrapper) -- zlib.decompress(data, wbits=-15).

This is implemented in tools/ac6_mode1_codec.py and wired into the extractor:

python .\tools\extract_ac6_pac.py <asset_root> --decompress

Compressed entries are written as files/DATA0x/compressed/<index>.decompressed.bin and the manifest records decompressed_count / decode_failures. Playing the game to pre-populate out/ac6_pac_runtime_dump is no longer required for compressed-entry extraction; it remains useful only for assets synthesized at runtime.

Prerequisites

• The game assets exist at:
  • C:\ext\New folder\AC6_recomp\out\build\win-amd64-relwithdebinfo\assets
• If you want runtime-decoded content included, you must already have:
  • C:\ext\New folder\AC6_recomp\out\ac6_pac_runtime_dump

To collect runtime dumps in future runs:

$env:AC6_DUMP_PAC_DECODED='1'
& 'C:\ext\New folder\AC6_recomp\out\build\win-amd64-relwithdebinfo\ac6recomp.exe'

Or use the launcher helper:

powershell -ExecutionPolicy Bypass -File .\tools\launch_ac6_with_pac_dump.ps1

That script sets AC6_DUMP_PAC_DECODED=1 and launches ac6recomp.exe for you.

One-Command Usage

From the repo root:

python .\tools\run_ac6_asset_pipeline.py

This uses the default paths:

• Asset root: out\build\win-amd64-relwithdebinfo\assets
• Raw PAC output: out\ac6_pac_extracted_raw
• Runtime dump input: out\ac6_pac_runtime_dump
• Typed FHM output: out\ac6_runtime_fhm_typed
• SWG output: out\ac6_runtime_swg_parsed
• Texture output: out\ac6_runtime_ntxr_exported

The wrapper prints a final JSON summary with the current corpus totals, including:

• PAC entries extracted
• runtime FHM container count
• parsed SWG files
• exported/skipped NTXR textures

Useful Variants

Use a custom asset root:

python .\tools\run_ac6_asset_pipeline.py --asset-root 'C:\path\to\assets'

Skip PAC re-extraction and only process existing dumps:

python .\tools\run_ac6_asset_pipeline.py --skip-pac-extract

Recommended workflow after a new play session:

powershell -ExecutionPolicy Bypass -File .\tools\launch_ac6_with_pac_dump.ps1
python .\tools\run_ac6_asset_pipeline.py --skip-pac-extract

Extract only PAC entries marked raw:

python .\tools\run_ac6_asset_pipeline.py --raw-only

Output Folders

• Raw PAC extraction:
  • C:\ext\New folder\AC6_recomp\out\ac6_pac_extracted_raw
• Parsed runtime FHM corpus:
  • C:\ext\New folder\AC6_recomp\out\ac6_runtime_fhm_typed
• Parsed SWG metadata:
  • C:\ext\New folder\AC6_recomp\out\ac6_runtime_swg_parsed
• Exported textures:
  • C:\ext\New folder\AC6_recomp\out\ac6_runtime_ntxr_exported

What To Open

• Main texture manifest:
  • C:\ext\New folder\AC6_recomp\out\ac6_runtime_ntxr_exported\manifest.json
• SWG manifest:
  • C:\ext\New folder\AC6_recomp\out\ac6_runtime_swg_parsed\manifest.json
• Example exported textures:
  • C:\ext\New folder\AC6_recomp\out\ac6_runtime_ntxr_exported

Notes About Texture Types

Not every texture is a normal color image.

The exporter now handles:

• Standard tiled R8 atlases
• Standard tiled RGBA8 atlases
• BC1 textures
• BC3 textures
• Packed-mip BC3 families
• Six-face BC1 assets using contact-sheet previews
• Several support textures stored as grayscale-in-ARGB

Some outputs are still valid but are things like:

• masks
• glyph sheets
• lookup textures
• normal maps
• cubemap-style faces

Current Status

At the time this guide was written, the texture exporter was producing:

• 845 exported textures
• 0 skipped textures

That count applies to the currently available runtime dump corpus.