A second camera on the far side of the water plane, rendering into a
half-viewport target that `enhanced_water.wgsl` reads BENEATH the
screen-space march — so SSR still wins wherever it finds something, and
the mirror only fills the hole SSR cannot reach: the ray leaving the
screen, and the top-edge fade, which is exactly where a shallow-angle lake
wants its far bank.
**It does not work yet, and it is not offered to anyone.** The mirrored
eye sits as far below the surface as the real eye sits above it — 26 yd
down on Lake Everstill — which is inside the lake bed, so the pass must
clip at the water plane or it renders sand. The clip is implemented
(Lengyel, adapted to this client's reverse-Z, around a finite far plane
because the oblique row makes depth affine and an infinite far collapses
every distant fragment onto one value) and it is WRONG: the mirror comes
back a radial smear. So this is `WOW_WATER_MIRROR=1`, a dev lever — no
CVar, no row in Options. It graduates to both, like every other lane,
once a capture shows a reflection instead of a starburst.
What IS established, and is why this lands rather than waiting:
- **With the lane off the water is byte-identical** to before the pass
existed, verified against a `git stash`ed build of the same tree.
- With it on it reaches the water and moves 63% of a lake frame — the
plumbing, the binding, the uniform and the composite all carry.
- Off, the plugin **registers nothing at all**, the posture
`static_gx::enabled` takes. That is not tidiness: `drive_mirror`
declares `ResMut<Assets<Image>>`, and merely registering it dormant
added 59 undeclared orders to `Update` and tripped the schedule ratchet.
Three things this cost, all of them now written into `docs/GRAPHICS.md`
and all of them my own:
1. **The pipeline failed to compile for most of a session while every A/B
read a clean zero.** The field is `clip_position`; `WaterFragment` has
no `position`. Naga refused the shader, the water fell back to another
path, and I measured the fallback over and over — including twice
mistaking the lake bed seen through clear water for a working mirror.
The client logs pipeline errors rather than panicking, by design, so
the answer was in the log the whole time. **Grep the capture log for
`error:` before believing any shader A/B.**
2. **A disabled lane is not automatically free.** Starting SSR's march
from the fogged `reflection` instead of `sky` looked equivalent and
moved 10.1% of a lake frame with the mirror switched off. The control
that catches that is diffing lane-off against a stashed build — not
against an older capture, which is what I reached for first.
3. **A flag colour has to be one the scene cannot produce.** My first
three "every gate passes" measurements were counting the orange lake
bed as my red flag, which sent the hunt in the wrong direction for an
hour.
The pass's own cost is deliberately unmeasured: it draws the scene a
second time, so it is the first item on the programme that spends main
thread, and pricing a broken render against item 1's view-distance table
would mean nothing. That happens when the projection does.
Verified: ALL GATES GREEN (591 s); `benilla-app --lib` against the install
at the exact 269-failure baseline, set-identical by `comm`.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01SgstFWtn1RxEJ5kVrpgYwn
gromandClaude Opus 5
355bac7b0e