578c71a1b9
Revert the mis-guided "triangle STRIP" reading (a937779): XBG7 index
buffers are triangle LISTS (prim=4 in the GPU capture; stored-normal
agreement 1.000 as a list vs ~0.49 as a strip). Reinstate the
winding-consistency gate.
Crack the grouped-pool layout used by the hero ship and ~150 detailed
models. A resource's sub-meshes share one index pool (buffers 4-byte
aligned, in descriptor-marker order) followed by one vertex pool (each
vtx_count*stride, same order); the vertex pool is 4-byte aligned after
the index pool. The whole resource is derived from one anchored pivot:
ib0 = vb0 - span - pad (pad in 0..=3, alignment)
ib[i] = align4(ib[i-1] + idx_count[i-1]*2)
vb[i] = vb[i-1] + vtx_count[i-1]*stride
vb0 is found via the unit-normal vertex-run scan; the alignment is
confirmed by validating the LARGEST sub-mesh (most reliable), after
which the rest are read/validated. A single marker reduces this to the
existing adjacency anchor, so grouped generalises it.
Results (cross-checked against a Canary GPU draw-log capture of
DeltaSaber_T.xpr):
- DeltaSaber_T f001 = body + 7 detail parts = 8650 tris, every sub-mesh
0-degenerate / full-coverage / winding-agreement 1.000.
- All 19 previously-declined weapon models now decode (they hit pad 2
and/or lead with a tiny bracket that broke a markers[0] pivot). Corpus
audit: 0/146 geometry files fail (was 19 -> flat-texture in the viewer).
- Stages unchanged (single-marker path is byte-identical; grouped falls
back to the old anchor on failure). 7/7 disc tests green incl. the
strict stage quality audit; new hero_ship_grouped_pool_decodes test.
Viewer: route by count_xbg7; --only matches an exact model name (so the
neutral pose renders without the mnv*/turn180 animation poses). Fix the
albedo matcher: match a sub-model to its _col map by entity stem
(e007_bdy_01 -> e007_col) instead of a full-name prefix, lifting stage
sub-model texturing from ~25% to ~95% (the rest were flat grey). Colour
correctness (channel order/sRGB) remains a separate dynamic-RE item.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Reverse-engineering knowledge base
This directory is the spec-side of the clean-room: it records what the original Project Sylpheed binary does (behaviour) and how its data is laid out, so that the Rust port can be implemented from these specs without re-deriving anything and without ever copying original code.
It exists to answer one question fast: "do we already know how X works, and how sure are we?"
The one rule that matters
Never document a claim more confidently than the evidence supports, and never paste original code here.
A wrong-but-confident note is worse than no note: someone builds on it and the bug hides for weeks. Every entry therefore carries an explicit confidence and its evidence. This mirrors the project method — measure the oracle, never infer; refute before believing.
Clean-room firewall
- ✅ Allowed: behaviour descriptions, field offsets/types, formulas, state machines,
observed input→output pairs, and references to the original by address
(
sub_821B68C0) or toxenia-rs/sylpheed.db. - ❌ Forbidden here and in
crates/: pasted decompiled C/C++ or verbatim disassembled function bodies presented as the thing to reimplement. Cite the address; describe the behaviour in your own words. Disassembly is a tool for understanding, not a source to copy.
Confidence levels
| Level | Meaning | Bar to reach it |
|---|---|---|
CONFIRMED |
Behaviour verified against ground truth. | ≥2 independent observations or one observation cross-checked against an oracle (canary framebuffer, a known-correct value, a second code path). |
PROBABLE |
Strong single-source inference. | One clean observation, or an unambiguous static read of the disassembly. |
HYPOTHESIS |
Educated guess, not yet tested. | Anything else. Must say what would confirm/refute it. |
Promotion requires new evidence, not re-reading the old evidence. A HYPOTHESIS that
"looks right again" is still a HYPOTHESIS. Only an independent check promotes it.
If evidence later contradicts an entry, demote it and record the contradiction — do
not silently edit the conclusion.
When to document
- Right after a function/structure crosses from
HYPOTHESISto at leastPROBABLE— before moving to the next code path, so the knowledge isn't lost or re-derived. - Whenever confidence changes (up or down) — append to the Evidence log, don't overwrite.
- Not while it's still a pure guess with no evidence — a one-liner in the relevant backlog/plan is enough until there's something to stand on.
What to document
- Functions/code paths →
docs/re/functions/<name>.md(one file per function or tight cluster). - Data structures / formats →
docs/re/structures/<name>.md. - Keep the index in
INDEX.md(one line each: name · confidence · one-line summary).
Use the templates: _TEMPLATE.function.md,
_TEMPLATE.structure.md.
How we find and confirm code paths (the toolchain)
Everything joins on the guest virtual address (PC) — code addresses are fixed by the XEX load, identical across our emulator and canary.
- Static (cheap, try first):
xenia-rs/sylpheed.db(DuckDB: 25 481 functions, xrefs, strings, vtables, imports). Query withxenia-rs/zq.py—zq.py grep <str>,zq.py xref <addr>,zq.py dis <lo> <hi>,zq.py fn <pc>. Entry points are usually a string (zq.py grep MSG_DEMO) or an import (movie/XMA API) xref'd back to the loader. - Dynamic (when static is ambiguous): run
xenia-rswith its probe suite —--pc-probe/--audit-pc-probe-hex(fires at block entry),--mem-watch(mid-block reads/writes of a VA),--lr-trace(call/return chains),--trace-instructions,--dump-addr(read guest memory). These already exist; prefer them over hacking canary. - Oracle (correctness ground truth): canary — the Wine cross-build
xenia-canary/build-cross/bin/Windows/Debug/xenia_canary.exe(the native Linux ELF crashes / does not run — do not use it). This is the only emulator that reaches the in-game menu; ourxenia-rsnever got past the intro video. Use canary to observe output (capture its framebuffer for texture colours), not usually to instrument code — though itsbuild-crosstoolchain does compile, so small C++ probes + rebuild are possible when needed. Run muted, one emulator process at a time, point it at the real ISO (not the symlink).
⚠️ VA-equality caveat: join code by PC (fixed), but never assume a data VA holds the same bytes across emulators — allocators differ. Compare data by content/layout.