re: withdraw "everything was read 16 bytes early" — the planes were right

The coordinator refuted the broad form of my claim and was correct to. The
older reading put section 2 at chunk+offset with the normal at intra-record
+16, which addresses exactly the same bytes as chunk+0x10+offset with the
normal at +0: on 3506e972 both put face record 0's normal at 0x1c700. Its
unit-normal and n·p+d results were measuring real planes and stand.

What is actually wrong is the record BOUNDARY, and it decides which record the
four integer words belong to — the face adjacency, i.e. the field the whole
correlation search was looking for. Settled: requiring own==f and
tet[A].faces[i]==f gives 100.000% with the block from record f and 0.000% from
record f+1, on all 11 objects.

Also audits my own numbers for the same defect the coordinator found in the
point-in-bbox test: most of them are content tests that address identical bytes
under either convention and have no power over the origin. The four that do
have power are listed, including that POF0 at base+0 would relocate the u16
counts and leave the section pointers unrelocated.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PMRJjbxLqZtsb5Vb7KunPE

docs/re/structures/regn-map-grid.md

@@ -435,12 +435,64 @@ Two things follow, and both are load-bearing:
 
 1. **The fixup base is `chunk + 0x10`, not `chunk + 0`** (`82465198`:
    `addi r3, r31, 16`). Every stored "offset" in a `REGN` file is relative to
-   file offset `0x10`. **Everything on this page above was read 16 bytes early.**
-   That single error is why twenty correlation tests returned chance.
+   file offset `0x10`, and every **record origin** on this page above is
+   therefore 16 bytes early.
 2. **The `POF0` table is an exact list of which words are pointers.** It is not
    a heuristic — it is the data the retail loader itself walks. Decoding it
    gives the pointer graph directly, with no guessing.
 
+### 🔴 A correction to how I first stated point 1
+
+The first version of this section said "everything on this page above was read
+16 bytes early", which is **too broad and I withdraw it**. For the plane fields
+it is *false*: the older reading put the section at `chunk + offset` and the
+normal at intra-record `+16`, which addresses **exactly the same bytes** as
+`chunk + 0x10 + offset` with the normal at `+0`. Its unit-normal and
+`n·p + d = 0` results were measuring real planes and stand unchanged. On
+`3506e972`, both conventions put face record 0's normal at file offset
+**`0x1c700` (116 480)** = `0x10 + 0x1c6f0`, where the header word at `0x78` is
+`0x1c6f0`.
+
+What is genuinely wrong is the **record boundary**, and it matters for one
+reason: it decides which 48-byte record the four integer words belong to — and
+those integer words are the face adjacency, i.e. precisely the thing the
+correlation search was hunting for. It also mis-resolves every stored pointer
+by 16 bytes, twice over along the cell → item → ref → tetrahedron chain, which
+is the mechanical reason that chain never landed on anything.
+
+### ✅ Which tests actually decide the origin — and which have no power
+
+Most of the numbers on this page are **content** tests and address the same
+bytes under either convention, so they cannot settle the origin. Stated
+plainly, because the same trap caught the point-in-bbox test:
+
+| test | discriminates the base? |
+|---|---|
+| section-5 targets on 96-byte boundaries; ref-array packing | ❌ no — `target − start` cancels the base |
+| face passes through 3 of 4 vertices; portal-cost identity | ❌ no — same absolute bytes either way |
+| sphere reaches its cell (98.7 % vs 18–28 %) | ❌ no for the base; it discriminates the **axis order** |
+| points inside the bbox (the older section) | ❌ no — a denormal reads as ≈ 0, which is inside a ±250 km box |
+| **the loader's own `addi r3, r31, 16`** | ✅ direct |
+| **where `POF0` says the header pointers are** | ✅ at `+0x10` the six relocated slots are exactly `0x70`–`0x84`, the six section pointers. At `+0` they would be `0x60`–`0x74`: the loader would relocate the `u16` **counts** and would leave the pointers at `0x78`–`0x84` unrelocated. Not merely wrong — non-functional. |
+| **what section-0 record 0 contains** | ✅ at `+0x10` a real vertex (`-250000, 250000, -250000` on `d4c89536`); at `+0` the two remaining header pointer words read as floats — `2.2e-40, 2.7e-40, 0` |
+| **the section-2 record boundary** | ✅ see below, 100.000 % against 0.000 % |
+
+### ✅ The record boundary, settled
+
+A tetrahedron names face `f`; the plane at record `f` is independently verified
+(three of the tet's four vertices lie on it, 100 %). The question is whether the
+adjacency block that says *"I am face `f`, my tetrahedra are A and B, at their
+face slots i and j"* sits in the **same** 48-byte record as that plane.
+
+Requiring `own == f` **and** `tet[A].faces[i] == f`:
+
+    adjacency block taken from record f      (base + 0x10) : 100.000 %
+    adjacency block taken from record f + 1  (base + 0)    :   0.000 %
+
+11 of 11 objects, every face, both sides. The plane and the four integer words
+that describe it are one record, and that record starts at `chunk + 0x10 +
+offset + 48·f`.
+
 `sub_82465138` is reached from exactly two callers, `sub_82461018` (vtable slot
 9 of the class at `0x820af8bc`, the pak/resource file class) and
 `sub_82461DE8`; both store `chunk + 16` as the object's data pointer, which
@@ -630,6 +682,8 @@ reason, and that is worth having on the page.
 | "record `+0x1c` is a bounding-sphere radius (ratio 1.001 on one object, 0.13–0.27 on the rest)" | 🟡 **half right** — `+0x0c` *is* a bounding-sphere radius, of the *tetrahedron*; the 1.001 was a coincidence of that map, where every tet shares the cube's circumsphere |
 | "`(count, offset)` pairs point at leaf arrays of `count × 4` bytes" | 🟡 **right mechanism, wrong record** — it is the cell *item* at `+0x10`/`+0x14` pointing into section 5, not the cell index |
 | "slots 8–11 are integers (denormal as float)" | ✅ correct, and they are the four vertex + four face `u16` indices |
+| "section 2 records are 48 bytes, unit normal, `n·p + d = 0` in 133 573/133 573" | ✅ **stands** — the same bytes under either origin convention; only the record boundary moves, see the correction above |
+| "section 0 points are inside the bbox, 13 467/13 467" | ⚠️ true but **uninformative** — it passes at either origin, because a denormal reads as ≈ 0 and 0 is inside the box |
 | "slot 7 is a local scale, ~14× smaller than the inter-node distance" | ✅ correct as measured — it is a *tetrahedron's* bounding radius, which is exactly that small |
 | "the BVH reading is refuted, no node sphere contains another" | ✅ stands, and is now explained: these are sibling tetrahedra, not a tree |
 | "the cell payload holds section-1 indices" | ✅ stands — it holds a **pointer to an array of pointers**, and no index anywhere |