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re: REGN is a tetrahedral navigation mesh — the cell→geometry link, decoded

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Found the reader. It is the deserialiser, not a consumer, and it answers the
question twice: the fixup base is chunk+0x10 (82465198 addi r3,r31,16), so
every offset previously recorded was read 16 bytes early — which is why twenty
correlation tests sat at chance — and the POF0 table names every pointer word
in the file.

Six sections, not four. cell {count,item*} → item {n@+0x10, refs*@+0x14} →
array of pointers into section 1 → a 96-byte tetrahedron. Section 2 is a face:
plane, its three vertices, the two tetrahedra either side (0xFFFF = hull) and
their face slots.

All 11 objects: face passes through exactly 3 of its tet's 4 vertices in
253 722/253 722 (random control 0.07–2.2 %); portal cost == face-centroid
distance in 380 460/380 460; sphere reaches its cell 98.7–100 % vs 18–28 %
with transposed axes.

Refuted and kept: 'REGN'/'MCOL' are never built as constants in the executable
(0x474E occurs zero times in 1.87 M instructions), so no magic-dispatch site
exists; and "zero portal-pair float marks a hull edge" shows no lift at all.
Still open: the runtime consumer of the grid, the second portal float, and the
four flag bytes at tetrahedron +0x54.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PMRJjbxLqZtsb5Vb7KunPE
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Sylpheed RE agent
2026-08-26 07:53:13 +00:00
parent 0d51cdb403
commit b9643c63f6
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docs/re/INDEX.md
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@@ -101,7 +101,7 @@ files, which is how the same ground got covered twice.
| [`structures/isl-message-dialogue-link.md`](structures/isl-message-dialogue-link.md) | Mission scripts as dialogue — built-in 64 -> message id -> caption text | ✅ CONFIRMED total, 2 683/2 683 call sites across all 28 stages resolve, no residue |
| [`structures/mission-objective-counter.md`](structures/mission-objective-counter.md) | `REMAINING OB` — the mission's own objective counter, in RAM | ✅ CONFIRMED for one Stage 02 run: a big-endian u32 whose value |
| [`structures/movie-subtitles.md`](structures/movie-subtitles.md) | Movie subtitles & the movie ↔ mission ↔ text chain | — |
| [`structures/regn-map-grid.md`](structures/regn-map-grid.md) | `REGN` — a per-map spatial grid (and `MCOL` beside it) | ✅ CONFIRMED for the header, which self-checks on all 11 objects on |
| [`structures/regn-map-grid.md`](structures/regn-map-grid.md) | `REGN` — a stage's tetrahedral navigation mesh (and `MCOL` beside it) | ✅ CONFIRMED — tet mesh + face adjacency + portal costs + uniform grid; decoded from the file's own `POF0` fixup table |
| [`structures/savegame-format.md`](structures/savegame-format.md) | Save file (`savedata`) — container ✅ exact, 3 fields named ✅, rest ❔ (2026-08-11) | ✅ CONFIRMED for the container and the chunk layout — parsed off the |
| [`structures/sound-slb.md`](structures/sound-slb.md) | Sound bank audio — `sound.pak` / `.slb` / XMA1 | — |
| [`structures/stage-definition-table.md`](structures/stage-definition-table.md) | Stage definition table and the squadron (`UnitGroup`) roster | ✅ for the record vocabulary and the stage→table wiring; |