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Modding Xenosaga III character textures — the human guide

How to recolor or repaint any character on the XS3 discs yourself, from "three commands" to "hex editor and a calculator." This is the process that produced pink KOS-MOS and pink Shion; everything here was verified against the real discs and confirmed rendering in PCSX2.

Byte-level format reference: chr-txy-format.md. Tool: chrtex.py (stdlib-only Python 3, no installs).

Everything here is also wired into the kit proper: cli.py exposes the same operations as chr-* subcommands with --flag arguments (see the README table), and the GUI has cards 10–13 for the common path (decode → export palettes → edit → import → ISO sweep). The examples below use chrtex.py directly because it is the shortest to type; swap in python3 cli.py chr-decode --chr file.chr --out dir/ etc. if you prefer the kit-style interface or are using the Windows release build (xeno-cli.exe chr-decode ...).

0. Quick start: pink Shion in three commands

cp -c "Xenosaga ... (Disc 1).iso" PINK.iso        # instant APFS clone
python3 chrtex.py iso-sweep PINK.iso shion         # recolor all 23 Shion .chr
# boot PINK.iso in PCSX2, load your save — pink hair

iso-sweep <iso> kosmos|shion [hue] recolors every matching character file in place and verifies each write by reading it back. Hue is 0..1 around the color wheel: 0.92 rose pink (default), 0.0 red, 0.33 green, 0.66 blue, 0.83 purple.

Always work on a copy of the ISO. cp -c on macOS clones instantly (copy-on-write) — you keep a pristine original for free.

1. The mental model (read this once)

  • Each disc hides its files inside big containers (X3.01, X3.02…) indexed by the Lba0/1/2.txt tables (offset|size|id|path per file). X3.01+X3.02 sit back-to-back in the ISO, so for any file in Lba0: ISO byte = 0x630800 + Lba0 offset. Same on both discs — Disc 2 carries identical copies at the identical location, so any Lba0 patch applies to both discs verbatim.
  • A character is a .chr file (e.g. \mdl\chr\pc\C3shion00.chr). Inside, the txy block holds all its textures: an image atlas of 8-bit indexed pixels plus 16×16-pixel palettes (CLUTs), one per material. A texture's color scheme is entirely in its 256-entry palette.
  • Because of that, recoloring never touches pixels — you edit a few hundred palette bytes and the whole hairdo follows. And because nothing on the disc is compressed, edits drop straight back in at the same size.
  • Each character has many .chr variants (costumes 00..NN, high-res cutscene models H00.., a low-LOD L00) and each variant has its own palettes (lighting is baked in — they are similar, not identical). A complete mod re-runs the same recolor on every variant; that's what iso-sweep automates. KOS-MOS = 27 files, Shion = 23.
  • Textures are named on disc (hair_longL02, shion_face00, kosmos_hada00 = skin, mayuge = brows, kutu = shoes…), which is how scripts and humans decide what to touch.

2. Get a file out and look at it

python3 chrtex.py iso-extract GAME.iso '\mdl\chr\pc\C3shion00.chr' shion.chr
python3 chrtex.py decode shion.chr out/

out/ now has one PNG per texture (numbered, named), plus _canvas_ct32.png (the raw atlas — you can literally see the palette tiles parked in it) and _atlas_index.png (the indexed image). Browse the PNGs to find what you want to change and note its name.

3. Pick your editing path

A. Scripted recolor (what the pink mods use)

pink-kosmos / pink-shion are worked examples on a single .chr; iso-sweep applies them disc-wide. Two selection strategies, worth knowing if you write your own:

  • Color-band filter (KOS-MOS): her hair is the only blue thing, so a "is this blue?" test over every palette entry is safe. One-liner rules, no name knowledge needed.
  • Tile policy by name (Shion): chestnut hair lives in the same warm range as skin, so color rules alone would bleed. Instead: palettes used only by hair textures get recolored wholesale; palettes shared with a face texture get a dark-warm band filter (light skin spared by a brightness ceiling); palettes touching skin/brow/eye names are left alone. Copy recolor() in chrtex.py and adjust the rules — it's ~30 lines.

B. Image editor (GIMP / Photoshop / Krita / Aseprite)

The palettes themselves are editable as images:

python3 chrtex.py export-palettes shion.chr pal/
#   pal/pal_224_112__shion_hair00.png   <- 16x16, one pixel per color
open -a GIMP pal/pal_224_112__shion_hair00.png
python3 chrtex.py import-palettes shion.chr pal/ shion_edited.chr

Each PNG is a 16×16 swatch grid: one pixel = one palette entry, in logical ramp order, alpha already un-scaled for you. Zoom to 1600%, use Hue-Saturation / Curves / hand-painting — anything, as long as you:

  • keep it exactly 16×16,
  • export as 8-bit RGB or RGBA, non-interlaced (every editor's default),
  • keep the filename (pal_<x>_<y>__<name>.png — the coordinates say which tile it goes back into; the name suffix is just a hint).

Only files present in the directory get imported, so delete the swatches you didn't touch. Gradient-mapping a hair ramp in an editor gives far more artistic control than a scripted hue rotation — ombre fades, two-tone, whatever you can paint into 256 pixels.

To preview: decode the edited .chr again and look at the PNGs before ever booting the game.

C. Repainting pixels (experimental)

python3 chrtex.py import-entry shion.chr shion_hair00 painted.png shion_edited.chr

Takes a PNG the same size as the texture and writes it into the atlas, quantizing every pixel to the texture's existing 256-color palette (nearest color; the palette itself is unchanged — combine with a palette edit if you need new colors). Good for drawn-on details in the texture's own color range: strand highlights, patterns, insignia. Limits: palette quantization can band smooth gradients, and overlapping atlas entries share pixels (the tool warns). Round-trip verified: reimporting a decoded PNG reproduces the original bytes' output exactly.

Faces on high-res H models are raw truecolor (fmt 0 in the decode listing) — import-entry doesn't handle those yet; everything else, including all hair, is paletted.

4. Put it back

Single file:

python3 chrtex.py iso-patch PINK.iso '\mdl\chr\pc\C3shion00.chr' shion_edited.chr

Size-checked, read-back verified. Repeat for each variant you edited (C3shion03, C3shionH00, … — the field model your save uses is the plain 00, so for a quick test that one file is enough; cutscenes use the H models).

Both discs: run the same commands against a Disc 2 copy — identical offsets, identical bytes.

For batches (or non-texture files), the general layer is repack.py: keep your edited files in a directory that mirrors the game tree and repack-tree patches them all at once — see REPACK.md.

The patched ISO also works on real hardware (burn / USB-load) — it's a plain same-size byte edit, no filesystem changes.

5. See it in-game

Boot the patched ISO in PCSX2. Two gotchas:

  • Savestates carry stale textures. A state made on the original ISO restores the old VRAM, so hair stays brown until the game re-streams the model (any map transition). Loading a memory-card save from the title screen always streams fresh from disc.
  • PCSX2's auto-resume state counts as a savestate for this purpose.

No checksums, no anti-tamper — the game reads whatever the LBA tables point at.

6. No tools at all: the hex-editor path

Everything above is arithmetic on the format spec; a hex editor (or xxd/dd) can do it. Worked example — KOS-MOS's main hair palette in C3kosmos00.chr:

txy block starts at file offset 0x3A980 (Xc header table -> txy entry + 0x40)
hair_longL02's palette tile sits at canvas (304, 32)
canvas row 32 lives in strip 2 (record table: data at txy+0xD790, 384 wide)
  -> tile row 0 = 0x3A980 + 0xD790 + 0x20 + (0*384 + 304)*4 = file 0x485F0
  -> 16 rows of 64 bytes, one canvas row (0x600 bytes) apart:
     0x485F0, 0x48BF0, 0x491F0, ... 0x4DFF0
in the Disc ISO the file starts at 0x630800 + 0x0CCF6000, so row 0 is at
     ISO offset 0xD36EDF0    (bytes there: 45 50 85 00 44 4F 83 00 ...)

Each 4-byte group is one R,G,B,A palette entry (alpha 0x00–0x80; the GS doubles it). 45 50 85 is a dusty blue — overwrite R/G/B, leave A, and that hair color is yours. The 16 rows are stored in CSM1 order (rows 8/16 of each 32-entry group swapped) — irrelevant for "recolor everything blue-ish," only matters if you care which exact ramp position an entry is. The spec doc has the full record/entry layouts if you want to find these offsets for any other file: the entry table gives every texture's palette position in plain little-endian, with its name right next to it.

7. What's still script-only or open

  • 2D art (menu portraits in kao/, battle faces) is a different, simpler format (linear XTX) — decoded by the browse pipeline, no importer yet, so a hair mod currently leaves portraits in the original color.
  • fmt 0 truecolor regions (H-model faces): decoded, not importable.
  • Length-changing edits (bigger textures) would need LBA/container rebuilding — nothing supports that yet; stay same-size.