Lane B R28 (v5.1): the awning fabric ripple — KILLED with the measurement

Ledger #2. Built it, proved it worked, measured what it was worth, killed it.
A 10x-over-driven billow — 1.4m of flap on a 0.14m canopy — cannot move 1% of
the frame. It is not the gain, it is the geometry. Nothing ships: buildings.js
and wind.js are byte-identical to HEAD.

IT WAS BUILT, AND IT WORKED. Split the stall canopies out of the rigid awning
InstancedMesh (own mesh, own subdivided box — a 4-corner box has nothing to
ripple), gave only them a cloth billow riding R17's wind.js uniforms: sin(pi u)*
sin(pi v) pin (zero at the four posts by construction), two crossed travelling
waves, per-instance phase so forty stalls don't breathe in unison. Proven by
rendered-pixel hashes, not by eye:
  cloth displaces (calm→gusty)        40f59eaf → d6d3e1f1  moves
  back to calm                        40f59eaf              identical
  uWindTime=99 at amp 0               40f59eaf              identical
  ?classic=1, pre- vs post-build      453c0154 → 453c0154   BYTE-IDENTICAL
  rest of town rides wind? (hidden)   76c8b518 → 76c8b518   still
  control: cloth back                 frame moves again
Cost at market_square, true A/B: +0 draws (98→98) / +2,160 tris. +0, not the +1
my own comment claimed — the square's chunks hold only stalls, so the rigid list
empties and makeInstanced returns null; the cloth mesh replaces it.

AND IT IS WORTH NOTHING (amp is the same multiplier as gain):
  0.02m  CALM, the default weather amp        0.05% of frame
  0.14m  STORM, the most a player ever sees   0.21%
  0.35m  2.5x over-driven                     0.33%
  0.70m  5x, absurd on a 0.14m slab           0.49%
  1.40m  10x, flapping a body-length          0.77%
At the player's actual browsing pose, storm-force: 0.00%, max delta 1. Not one
pixel.

THE REASON IS PHYSICAL — the same physics that killed the verandah in R17. A
canopy is a horizontal sheet at y2.2 seen by a 1.7m player: edge-on or from
underneath, so vertical displacement runs almost parallel to the view ray and
makes almost no pixels. You cannot see a flat horizontal sheet flex vertically
while standing under it. No gain fixes it; 10x buys 0.77% and stops reading as
cloth.

WHAT WOULD WORK (for whoever reads this in round 35): the motion must be
perpendicular to the view — VERTICAL cloth: hanging stall skirts, a flag, a
banner, an awning valance. That is an ASSET (Lane E), not a shader. B's
applyWind/applyFabricWind seam is ready the day such a mesh exists; the shader
was never the missing piece. Ledger #2 leaves the backlog forever.

TWO VACUOUS MEASUREMENTS CAUGHT ON THE WAY. (1) `!!material.onBeforeCompile` to
prove the rigid verandah untouched — every THREE.Material inherits a prototype
no-op, so it is ALWAYS truthy; the assert could never go red. Replaced with
hasOwnProperty + a behavioural hide-and-hash control. (2) A gain sweep reporting
an identical 0.21% at gains 0.4→4.0 because I never stored the shader ref, so
uFabricGain never moved — four identical numbers across a 10x range is a sweep
that proves nothing. The constancy, not the value, gave it away. Both would have
passed as green.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

docs/LANES/LANE_B_NOTES.md

@@ -1,5 +1,72 @@
 # LANE B — NOTES (measured)
 
+## Round 28 (v5.1) — ledger #2, the awning fabric ripple: **KILLED with the measurement**
+
+**Built it, proved it worked, measured what it was worth, and killed it. A 10×-over-driven billow —
+1.4 m of flap on a 0.14 m canopy — cannot move 1% of the frame. It is not the gain; it is the
+geometry. The backlog item is closed permanently, and the reason names what *would* work.**
+
+R17 shipped tree sway and parked this with a physical reason: a posted verandah is a structural roof
+and does not flutter. R28 asked for the half R17 left — the stalls' striped canopies really are cloth,
+and they shared the rigid awning InstancedMesh, so neither could move without the other. That part was
+all true, and the split worked. The cloth just turned out to be invisible.
+
+### It was built, and it worked
+Split the canopies out of the rigid mesh (own `InstancedMesh`, own subdivided box — a 4-corner box has
+nothing to ripple), gave only them a cloth billow riding R17's existing `wind.js` uniforms: a
+`sin(πu)·sin(πv)` pin (zero at the four corner posts by construction, peak mid-panel), two crossed
+travelling waves, per-instance phase off world position so forty stalls don't breathe in unison.
+Proven by **rendered-pixel hashes**, not by eye:
+| proof | result |
+|---|---|
+| the cloth actually displaces (calm vs gusty) | `40f59eaf` → `d6d3e1f1` — **moves** |
+| returning to calm reproduces the calm frame | `40f59eaf` — **identical** |
+| `uWindTime = 99` at amp 0 | `40f59eaf` — **identical** (amp 0 ⇒ `+= …*0.0`, the R17 pattern) |
+| **`?classic=1`, same fixed pose, pre- vs post-change build** | **`453c0154` → `453c0154` — byte-identical** |
+| rigid verandahs / rest of town ride the wind? | cloth+trees hidden: `76c8b518` → `76c8b518` — **still** |
+| …and the control proves I hid the right thing | cloth restored: frame **moves** again |
+Cost at `market_square`, true A/B: **+0 draws** (98 → 98) / **+2,160 tris**. +0, not the +1 I'd written
+in my own comment — the square's chunks hold *only* stalls, so the rigid list empties, `makeInstanced`
+returns null, and the cloth mesh replaces it rather than adding to it.
+
+### And it is worth nothing — the sweep (amp is the same multiplier as gain)
+| peak billow | frame changed |
+|---|---|
+| **0.02 m — CALM, the default weather amp** | **0.05%** |
+| **0.14 m — STORM, the most any player ever sees** | **0.21%** |
+| 0.35 m (2.5× over-driven) | 0.33% |
+| 0.70 m (5×, absurd on a 0.14 m slab) | 0.49% |
+| **1.40 m (10×, a canopy flapping a body-length)** | **0.77%** |
+At the player's actual browsing pose, storm-force: **0.00%, max channel delta 1**. Not one pixel.
+
+**The reason is physical, and it is the same physics that killed the verandah in R17.** A canopy is a
+horizontal sheet at y 2.2 viewed by a 1.7 m player: you see it edge-on or from underneath, so a
+*vertical* displacement runs almost parallel to the view ray and produces almost no pixel change. You
+cannot see a flat horizontal sheet flex vertically while standing under it. No gain fixes that — 10×
+buys 0.77%, and anything that large stops reading as cloth and starts reading as a trampoline.
+
+**What would work, if wind in the market is ever wanted (for whoever reads this in round 35):** the
+motion has to be *perpendicular* to the view, which means **vertical cloth** — hanging stall skirts, a
+flag, a banner, an awning valance. That is an **asset** (Lane E), not a shader. B's `applyWind` /
+`applyFabricWind` seam is ready for it the day such a mesh exists; the shader was never the missing
+piece. **Ledger #2 leaves the backlog forever.**
+
+### Kept from the round
+Nothing shipped: `buildings.js` and `wind.js` are byte-identical to HEAD. Shipping an invisible ripple
+would have cost 2,160 tris and a second draw path in the covenant town to move 0.05% of a calm frame.
+*The R17 rule was "ships or dies". It died — and it died with numbers, which is the only way an item
+this old stops coming back.*
+
+**Two vacuous measurements caught on the way (the epoch's own disease, still catching me):** (1) a
+`!!material.onBeforeCompile` check to prove the rigid verandah was untouched — every `THREE.Material`
+inherits a prototype no-op, so it is **always** truthy; the assert could never go red, and I replaced it
+with `hasOwnProperty` plus a behavioural hide-and-hash control. (2) a gain sweep that reported the
+identical 0.21% at gains 0.4→4.0 because I never stored the shader ref, so `uFabricGain` never moved —
+**four identical numbers across a 10× range is a sweep that proves nothing**, and it was the constancy,
+not the value, that gave it away. Both would have passed as green.
+
+---
+
 ## Round 27 wave 4 — `poseForShopFront` shipped · **and every real town's shops face away from the street**
 
 **The micro-task is done and verified. In doing it I found why F photographed empty road: it is not