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re: open MCOL -- same container as REGN, same map parameters

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MCOL sits beside REGN in hidden/MiscBin.pak, 11 of each, never decoded. Over all
11: POF0 at data_size+16 11/11, bbox pad words 1.0/1.0/0.0 11/11, and
extent == max-min 11/11. So the header prefix is the same shape as REGN's and
the POF0 mechanism applies, which means the chunk+0x10 base and the loader's own
pointer list -- the two things that cracked REGN -- are available here too.

The map parameters are not merely similar but identical in distribution: bboxes
2/6/3 at 250k/50k/25k and the 0x40 triple 2 at 50000 and 9 at 10000, matching
REGN exactly. Eleven maps, each with an MCOL and a REGN over the same volume at
the same cell size. Noted that this matches distributions, not a demonstrated
object-to-object pairing.

Everything past 0x40 diverges from REGN and is open. Also recorded that my own
POF0 delta decoder is wrong here -- eight leading zero deltas -- and that the
working one is regn_decode.py on auto/regn-reader, which should be used rather
than re-derived. Re-deriving it is the mistake I made.
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Sylpheed RE agent
2026-08-26 08:18:17 +00:00
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docs/re/INDEX.md
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| [`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/mcol-collision.md`](structures/mcol-collision.md) | `MCOL` — same container and map parameters as `REGN` | 🟡 OPENED — `POF0` at `data_size+16` 11/11, bbox pad words 11/11, `extent == max−min` 11/11, and bbox + cell-size distributions identical to `REGN` (2/6/3 and 2/9); everything past `0x40` ❔ |
| [`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/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 | — |

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# `MCOL` — the same container as `REGN`, and the same map parameters
**🟡 Opened 2026-08-26.** `MCOL` sits beside `REGN` in `hidden/MiscBin.pak`, 11
of each, and has never been decoded. This page establishes what it shares with
`REGN` — which is a lot, and gives the next attempt a large head start.
## ✅ Same container
Over all **11** objects:
| | |
|---|---|
| `POF0` fixup table at `data_size@+4` + 16 | **11 / 11** |
| bbox pad words are `1.0` / `1.0` / `0.0` at `+0x1C`, `+0x2C`, `+0x3C` | **11 / 11** |
| `extent == max − min` for the `0x30` block | **11 / 11** |
So the header prefix is byte-for-byte the same shape as `REGN`'s: magic, data
size, then bbox min / bbox max / extent as `f32[4]`, then a triple at `0x40`.
The `POF0` mechanism applies, which means **the `chunk + 0x10` base and the
loader's own pointer list are available here too** — the two things that cracked
`REGN`.
## ✅ And the same map parameters, exactly
The bounding boxes and the `0x40` triple are not merely similar — the
distributions are **identical**:
| | `MCOL` | `REGN` |
|---|---|---|
| bbox ±250 000 | 2 | 2 |
| bbox ±50 000 | 6 | 6 |
| bbox ±25 000 | 3 | 3 |
| `0x40` = 50 000 | 2 | 2 |
| `0x40` = 10 000 | 9 | 9 |
Eleven maps, and for each one an `MCOL` and a `REGN` describing the same volume
at the same cell size. `0x40` is the **cell size** in `REGN`; the same values in
the same multiplicities here is strong evidence it is the cell size in `MCOL`
too — though note this is a match of *distributions*, not a demonstrated
object-to-object pairing, which would need the two linked by name or by a stage's
tables.
## ❔ What is not yet known
* **Everything past `0x40`.** `MCOL`'s words at `0x50`–`0x84` do **not** look
like `REGN`'s (`REGN` has grid dims at `0x50`, six `u16` counts at `0x60` and
six section pointers at `0x70`; `MCOL` has a large value, two mid-range values
and `112` at `0x50`, mostly zeros at `0x60`, and `0x05050501` at `0x70`). The
headers agree on the spatial prefix and diverge after it.
* **My `POF0` delta decoder is wrong here** — it emits eight leading zero deltas
before plausible offsets, so either the stream has a preamble I am not
skipping or my 6/14/22-bit reading is off. The working decoder is
`tools/re-capture/regn_decode.py` on branch `auto/regn-reader`; **use that
rather than re-deriving it**, which is the mistake I made here.
**First step for whoever continues**: run the known-good `POF0` reader over an
`MCOL`, list which words are relocated, and read the header slots those pointers
occupy. That is exactly the move that turned `REGN` from twenty failed
correlations into a decode.