Lane C R16 (v3.1): stage.backline[] amp unification, drop primitive ampStacks (ledger #5, C half)
C exposes room.stage.backline[] — 2 seeded up-stage amp slots {x,z,ry,y} (pure data) — and
drops its primitive ampStacks from placeStage. Lane D plants E's guitar_amp GLB at backline[0]
(D's primitive fallback under ?noassets): one unified backline, GLB when present.
- backline[0] = (stage.x + stage.w*0.36, deckY, stage.z - stage.d*0.22) == D's R15-verified amp
pose exactly, so plumbing D's plant to backline[0] moves nothing on screen. backline[1] = spare
stage-left mirror. ry=pi (audience-facing), y=deckY.
- Verified fresh (seed 20261990): slots up-stage, on-deck, clear of all 4 bandPoses (nearest-bass
0.87 pub / 0.70 band_room / 0.92 rsl) and all watchPoints (>=1.95 m); determinism byte-identical;
0 leftover ampStack groups; drawSweep venues 122/120/131 (was 126/124/135, -~4 draws each) <=350.
- Determinism/golden-safe: dropping the amp loop only drops draws on the 'stage' sub-stream (nothing
downstream reads it); placement snapshot excludes ampStacks; interiors aren't hashed; ?classic has
no venues. Disjoint from F's flip. LANE_C_PUB §3 amended (v3.1 marker).
C->D handshake: backline shape live. Verify with D once the GLB is wired at backline[0].
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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