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revert(mesh): withdraw the neighbourhood anchor -- it regressed the e106 twin mirror

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The neighbourhood anchor (f18d591) and its refinement (27a0701) took
cross-container inconsistency from 125 to 51 with coverage unchanged, and made
e106 render as a destroyer rather than a slab. Both are reverted.

ship::tests::static_assembly_matches_runtime_capture is gated on SYLPHEED_ISO, so
it SKIPS in an ordinary cargo test -- which is why the regression was invisible
in every suite run so far. With the ISO it fails:

  e106_bdy_01: static M row0 [-1.0, 0.0, 0.0] != captured [1.0, 0.0, 0.0]

e106_bdy_01 and _02 are a mirrored pair whose two buffers hold the same geometry
reflected in X, and BOTH resources currently decode to the SAME buffer (identical
counts, span and mean_x). apply_twin_mirrors picks which instance to reflect from
the sign of that mean_x, so which buffer wins flips the decision:

  before  both twins mean_x = -66.83  -> mirror bdy_02  (matches the capture)
  after   both twins mean_x = +66.83  -> mirror bdy_01  (contradicts it)

Neither is right -- two resources sharing one decode is itself the bug and the
mirror heuristic has been compensating. The capture is ground truth, so a change
that contradicts it does not ship. The real fix must give each twin its own
buffer first.

Kept from the attempt: this test now also asserts the SET of static placements
against the capture (allow-list {e303_wep_01} for vbase dedup), so extra
placements can finally fail it -- the direction it could never fail in before.

Docs, backlog, INDEX and the ignored test's message all corrected to say
diagnosed-not-fixed rather than fixed.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
This commit is contained in:
Claude (auto-RE)
2026-08-12 01:08:41 +00:00
parent 0f9c95c52e
commit 64d372c7e8
6 changed files with 85 additions and 159 deletions
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47
docs/re/structures/xbg7-mesh.md
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@@ -393,7 +393,7 @@ and prefer candidates close to the previous resource's anchor), falling back to
first-match when there is no neighbour yet. That needs no new format knowledge,
and it selects `52 257 440` here.
### ✅ Implemented (2026-08-12) — inconsistency halved, coverage unchanged
### ⚠️ WITHDRAWN (2026-08-12) — it halved inconsistency but regressed the twin mirror
`anchor_pool_mesh_near` tries candidates in order of distance from a reference,
and `anchor_models_filtered` runs **two passes**: pass 1 anchors first-match to
@@ -402,22 +402,47 @@ learn where resources land, then pass 2 re-anchors each resource preferring its
with too few anchored neighbours keeps pass 1's result, so nothing regresses to
guesswork.
| | decoded | shared | inconsistent |
|---|---|---|---|
| before | 5 480 / 6 294 | 681 | **125** |
| neighbourhood anchor | 5 480 / 6 294 | 681 | **63** |
| + refining the map | 5 480 / 6 294 | 681 | **51** |
| | decoded | shared | inconsistent | e106 mirror |
|---|---|---|---|---|
| shipped (today) | 5 480 / 6 294 | 681 | **125** | ✅ matches capture |
| neighbourhood anchor | 5 480 / 6 294 | 681 | 63 | ❌ flipped |
| + refining the map | 5 480 / 6 294 | 681 | 51 | ❌ flipped |
**Refining matters** because pass 1's anchor map contains the very mistakes the
neighbourhood is meant to correct, so a resource beside a mis-anchored neighbour
inherits a bad reference. Re-anchoring against the improving map and repeating
converges quickly — two rounds, with a third changing nothing.
**Coverage is unchanged and inconsistency halves.** `e303_wep_01` now decodes to
49 × 23 × 42 in *all* containers, and `e106` renders as a destroyer instead of a
slab ([before](../captures/e106-static-assembly-volume-bug.png) ·
[after](../captures/e106-static-assembly-fixed.png)) — its two shared turrets sit
symmetrically at X[−203,−154] and X[154,203].
On its own metric this looked complete: coverage unchanged, inconsistency
halved, `e303_wep_01` decoding to 49 × 23 × 42 in *all* containers, and `e106`
rendering as a destroyer instead of a slab
([before](../captures/e106-static-assembly-volume-bug.png) ·
[after](../captures/e106-static-assembly-fixed.png)).
**It was reverted anyway.** `ship::tests::static_assembly_matches_runtime_capture`
is gated on `SYLPHEED_ISO` and therefore skips in an ordinary `cargo test`; run
with the ISO it fails:
```
e106_bdy_01: static M row0 [-1.0, 0.0, 0.0] != captured [1.0, 0.0, 0.0]
```
**Why:** `e106_bdy_01` and `e106_bdy_02` are a mirrored pair whose two vertex
buffers hold the same geometry reflected in X, and **both resources currently
decode to the *same* buffer** — identical vertex count, identical span, identical
`mean_x`. `apply_twin_mirrors` decides which instance to reflect from the sign of
that `mean_x`, so which of the two buffers gets picked flips the decision:
```
before the change both twins decode with mean_x = −66.83 → mirror bdy_02 (matches the capture)
after the change both twins decode with mean_x = +66.83 → mirror bdy_01 (contradicts it)
```
Neither is right: two distinct resources sharing one decode is itself the bug,
and the mirror heuristic has been compensating for it. The runtime capture is
ground truth, so a change that contradicts it does not ship — **the real fix must
give each twin its own buffer**, after which the mirror rule can use each
resource's own geometry.
**The filtered path needed care.** `models_named` (what the viewer's ship
rendering uses) drops non-wanted resources, which would leave a filtered decode