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ReaperOfVeriod 85fa9d1432 Locate the tfrag terrain region and record what its records look like

The core header field at 0x08 is zero on all 27 levels, and the seven offsets
0x0c, 0x10, 0x14, 0x60, 0x64 and 0x68 are strictly increasing on every level.
Reading them as a sequence of region boundaries gives the layout of core_data:

  tfrag      [0, occlusion)
  occlusion  [occlusion, sky)
  sky        [sky, collision)
  collision  [collision, textures_base)

So tfrag = 0 is a real value rather than a missing field, and the terrain is the
first 2.12 MB of level 0's geometry.

The terrain begins with a short header followed by a repeating 64-byte record
from 0x40. Established about those records: byte columns 3, 7, 11 and 15 are
0x48 in every record, which are high bytes of four s16 values giving a near-fixed
Y on a planet of radius about 2,187; columns 16 and 17 increase steadily across
records like a grid walk; and columns 48-51 carry a repeating ffff00ff pattern
characteristic of GS packet headers.

The record layout itself is not yet recovered, and the write-up says so rather
than guessing. Ruled out and recorded: uncompressed f32 vertices (the longest
plausible float run in 16.9 MB is a run of zeros in the collision block, so
vertices are packed); GS packet tags at every position (0xE0..0xEF is frequent
but uniform, which is what packed data looks like); and a 48-byte record stride
(the pattern repeats at 64).

Also confirmed this session: the core header base is offset 0 with certainty,
because the compressed and decompressed sizes of core_data appear at the same
offsets (0x88 and 0x8c) in all 27 levels' core_index. And the occlusion block at
the header's 0x0c offset reads as an ascending u16 array of 65 values before
restarting, consistent with per-cell visibility records.

No code change: this is the reverse-engineering record for the next parser. 75
unit tests, clippy clean.

2026-10-09 16:32:42 +02:00

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Roadmap

Status as of 2026-10-09.

A from-scratch native Rust reimplementation of Ratchet & Clank: Going Commando (PS2). Each phase ends in a gate — something checkable, not a feeling that it is going well. Phases are ordered so that the riskiest unknowns are retired early, while they are still cheap to retire.

Where we are

Target disc identified and verified (SCUS_972.68 v1.01, NTSC 60 Hz)
Workspace builds (cargo check --workspace)
Repository hygiene in place (pre-commit guard, .gitignore, licence record)
Phase 1 complete. The disc pipeline runs end to end and is verified against a committed hash table: 5,135 files, 4,500,106,960 bytes, every one of the 92 asset containers parsing.
Phase 2 in progress. Level containers are parsed through their typed header, and the data extent is parsed as a container of byte ranges. The geometry decompresses: level 0 yields 16,969,296 bytes of level content from a 9.7 MB stream.
Next: the geometry directory's class tables, then tfrag terrain.

The disc being the exact build the reference projects pin is the single biggest favourable fact so far: no disc conversion, no regional timing work, and no re-derivation of the reference baseline.

Phase 0 — Foundation ✅

Done.

Disc identified: SCUS_972.68 v1.01, USA Black Label, NTSC 60 Hz. Boot ELF SHA-1 bacda860cbd6723142e86db56f197e47e728970f, entry 0x00131AE8 — the entry point independently matches the value recorded by rac2-gc-decomp, which cross-confirms the identification.
tools/identify-disc.py reproduces the identification against any disc image and distinguishes a truncated dump from a non-PS2 image.
Five-crate workspace scaffolding, Bevy 0.19.1 pinned, builds clean.
.githooks/pre-commit blocks game data. Verified against seven cases: .iso, renamed disc image, WAD container, ADX container, extracted/, a 60 MiB file, and legitimate source.
AGENTS.md and PROVENANCE.md record conventions and licences.

Open from this phase

alsa-lib-devel is not installed, so Bevy's host audio backend is disabled in Cargo.toml. Audio is the last phase; revisit then.
Bevy feature set is deliberately minimal. Re-add features as needed rather than switching default-features back on wholesale.

Phase 1 — Disc pipeline ✅

Done. Gate met: every extracted file matches the committed hash table.

iso9660 reader (R&C2 lists assets as real files, unlike R&C1)
G/*.WAD container header parsing — 92 containers, three table shapes
WAD LZ77 decompression (wad.rs, four packet classes)
Unpack every container, bounds-checking each extent
SHA-1 table for all 5,135 files (hashes only, never content)
verify stage, plus integration tests against a real disc
Format specs written: disc-layout.md, global-wad.md, wad.md
Work record with the negative results: plan/disc-pipeline.md

gc-extract identify disc.iso        -> SCUS_972.68 v1.01 NTSC, ELF SHA-1 matches
gc-extract unpack   disc.iso out/   -> 5135 files, 4,500,106,960 bytes, 10.8s
gc-extract verify   out/ table.tsv -> OK: 5135 files match

Not done, deliberately: the table of contents at sector 1001 is documented but not read. Enumerating the ISO filesystem is simpler and sufficient; the ToC matters when per-level overlay loading is understood in Phase 3.

Two wrong turns are recorded in plan/disc-pipeline.md, because both would be easy to repeat: the container pair table read backwards, and the LZ77 stream mistaken for a bit stream. Both produced plausible-looking wrong output before failing, which is the failure mode worth guarding against.

Phase 2 — Format parsers

Goal: every asset type parses into plain Rust values, tested against real disc data.

Phase 1 hands over the extents; this phase works out what each one contains.

Done so far:

level_wad.rs — the 0x60-byte header on all 27 level containers, naming four extents plus three chunk descriptors. Verified: extents tile each container in file order (27 of 27).
Two facts the format documentation does not state, both measured here: sizes in this header are sector counts where the generic G/ table uses byte counts, and LEVEL21.WAD reports level id 30, so container order is not level identity.

In progress:

data — the extent header locates core_index and core_data; the geometry decompresses and is verified on level 0.
core_index class tables — the header base is confirmed (the compressed and decompressed sizes of core_data sit at the same offsets in all 27 levels), and every offset lands inside core_data. But the class-table fields do not decode under any field order or stride tried. Ruled out and written up in plan/level-assets.md. Next: identify tfrag by its own structure instead of through the header.
occlusion and sky offsets located and their first bytes read.
gameplay — begins WAD + a per-level byte, and does not decode with the WAD LZ77 decoder. All 27 levels fail identically, so the input is wrong rather than the decoder. Ruled out: bit order, header length, the LZ77 framing. Hypotheses queued in plan/level-assets.md.
occlusion — 2 to 25 sectors, small enough to read whole.
sound_bank — SBlk and DAW signatures found in all 27.
data — the large one: 4.2 to 21.9 MB of geometry per level.
tfrag — terrain: LOD chains, strips, morph targets
tie — instanced environment geometry, fat vertices
shrub — foliage and decorative meshes
moby — dynamic actors; moby_anim — skeletal animation
collision — cells, packed vertices, faces
occlusion — the PVS grid
sky, volumes, textures (CSM1 CLUT + PS2 alpha)
level_overlay — the seven-section parser and relocation from Phase 3

Gate: every parser has a golden test against bytes from the real disc, and reports mismatched header counts as failures rather than warnings.

Discipline: bound every read. Typed errors, no panics, no reads past the buffer.

Phase 3 — Overlay system

Goal: make 27 level overlays tractable.

Every overlay carries the same seven sections (.lit, .bss, .data, lvl.vtbl, lvl.camvtbl, lvl.sndvtbl, .text) and the same engine code, linked at different addresses. ReRAC solves this by masking relocations — j/ jal targets, lui immediates of main-RAM addresses, the %lo that completes them, and $gp-relative operands — then matching the masked words to find a reference function's copy on another overlay.

Port the masking and code-identity logic
Relocation::func and Relocation::data
$gp for this game (0x001AEFF0, against R&C1's 0x166c00)
Extend the level table from 19 to 27

Gate: every level-01 function's relocated copy is found on all 27 overlays; cross-checked against an independent cluster hash.

Why this is high-value: it turns "27 overlays of unknown code" into a table lookup, and it is the main thing inherited from ReRAC.

Phase 4 — Engine core

Goal: draw a frame.

Graphics Synthesizer in wgpu, with the GS's own rules: its round(log2(z/n) + K) mip selection, blend and alpha-test behaviour, alpha 0x80 meaning 1.0, CLAMP wrap
VU0/VU1 skinning and lighting on the PS2 float model
LOD/morph/cull per TfragProc and TieProc
Occlusion culling, fog, shadows
GIF/VIF packet stream interpretation

Gate: CPU and GPU paths agree on every vertex of a reference level — the same identity check ReRAC runs.

Risk: VU1 microcode is binary in the game's .vutext section, so it is reverse engineered rather than parsed. This is the hardest single item in the project and the main threat to the timeline. Note that ReRAC's own moby VU1 analysis trips their disassembler on two opcodes.

Phase 5 — Veldin vertical slice

Goal: one planet, playable start to finish.

Ratchet's controller on a spherical planet
Chargeboots: hold/release timing, chained jumps, dash
Wrench and the camera
Collision and the HUD

Gate: Veldin is completable and visually matches PCSX2 frame-for-frame under replayed input.

This is the go/no-go for the project. If Veldin works, the other 26 levels are content. If it does not, the reason is discovered while it is still cheap. Spherical gravity is the thing most likely to break, because it invalidates R&C1's movement and camera assumptions wholesale.

Phase 6 — Remaining overlays and the shell

Per-level moby class dispatch via lvl.vtbl
Remaining 26 levels
Planets, travel, the Gadgetron vendor, RPG upgrades
Weapon modification bitmasks (lock-on, shock, acid, …)
Minigames and challenges
The 25-state memory-card FSM and its UI
IFF chunk saves, including import of a R&C1 save to unlock legacy weapons

Phase 7 — Audio and video

989snd v2 audio decode and playback (not CRI ADX — a different codec)
SPU2 mixing, reverb zones, level sounds
IPU/MPEG-2 video for the title screen and cutscenes

Phase 8 — Fidelity pass

Differential testing against PCSX2 across every level:

Recorded-input frame comparison, per planet
Geometry, fog, blend, alpha, texture sampling
Audio sync and 60 Hz timing
Behavioural comparison: traversal routes, boss timing, RNG

Principles

A gate is pass/fail, not a percentage. "Looks fine" is not progress.
Negative results are written down. A ruled-out approach saves the next attempt as much as a working one.
The float model is not negotiable. Approximate is not the same as faithful, and the difference is visible in how the game feels.
Fidelity over tidiness. Where the original does something that looks like a bug, reproduce it and say why in a comment. See AGENTS.md.

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