Wall batching stays live in cutaway

[wass08]

Metric

Charter backlog 3c: idle frame cpu in cutaway should match the full-height number on the rich fixtures (the mode users edit in loads walls unbatched today).

What changes

Cutaway never changes wall geometry: WallCutout (viewer, useFrame priority 0) swaps each wall's material array by camera facing and stamps userData.wallHidden. The merged wall batch already released tinted walls every frame, so hidden walls take the same path — released the frame the stamp appears (this system runs at priority 5, same frame), excluded from candidates and from the re-merge drift count, re-sewn at settle when they come back. Mode flips between up and cutaway no longer dispose every level. down, translucent and isolation still stand the batch down.

window.__wallBatch.stats() is exposed under ?perf so scripted runs can read wall batch membership (the panel's batch row only covers node batching).

Before / after (private scripts/perf/run-scaling-matrix.ts, same machine, load avg 5–6)

fixture	mode at load	idle frame cpu	post-hover idle
rich 4× (356 walls, 540 items)	cutaway	16.9 → 14.0 ms (−17%)	18.9 → 15.9 ms
rich 2×	cutaway	8.4 → 8.4 ms	8.6 → 8.4 ms
tower 2×18	full height	11.1 → 9.5 ms	11.6 → 10.2 ms
Maxi 8×	full height	15.2 → 18.0 ms (noise; identical code path)	19.0 → 22.2 ms

Wall mode is persisted per project, so only the rich fixtures load in cutaway. In-page probe on the PR build: cutaway batches 164 of the rich-4× walls (172 hidden), 82 on rich-2×, 160 on Maxi-4×; cutaway vs full-height frame cost within 5 % on all three; draws −350…−580 at the load pose.

Gates

• bun test packages/nodes: 1888 pass. New unit coverage: hidden walls are not candidates, a batched wall is released the frame its stamp appears, hidden walls do not count toward the re-merge threshold, released walls re-sew once visible and settled.
• E2e against the PR build: perf-regression pack 5/5, click-batched-wall, click-hidden-wall, opening-placement-preview green; placement-preview-follows-cursor fails identically on base (pre-existing).
• Visual parity (canvas screenshots, cutaway load pose / after orbit / full height / cutaway again): ≤ 0.28 % differing pixels on rich 2×/4×; Maxi 4× post-orbit poses differ by an orbit end-pose shift only.
• Bake parity: Maxi 1× and rich 2× bakes identical in triangles, meshes, primitives, nodes and materials.

Follow-ups (not here)

Camera flips still cost a re-sew at each orbit stop in cutaway; keeping hidden walls resident (or moving walls onto NodeBatchStore) removes that. The rich-4× < 12 ms target needs ceilings + slabs coverage on top.

🤖 Generated with Claude Code

https://claude.ai/code/session_01Jmmz2AMwTzcnKsSHHPEMhN

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Note

Medium Risk
Changes core rendering batching and cutaway interaction timing; mistakes could cause wrong walls drawn, missing picks, or hover glitches, though coverage is strong.

Overview
Wall merging now stays enabled in cutaway instead of tearing down every level batch on mode entry. canBatchWalls treats cutaway like up; down, translucent, and isolation still suspend batching.

Cutaway-hidden walls are handled like hover/selection releases: meshes stamped userData.wallHidden are skipped as batch candidates, released from the merged mesh the same frame the stamp appears (after WallCutout at priority 0), and excluded from the settle re-merge count so the batch can stay stable while most walls remain merged. When a stamp clears, the level is marked stale so visible walls re-sew after the usual settle window.

Re-merge and candidate collection use a combined excludedNodeIds set (cutaway-hidden plus tinted walls). ?perf sessions get window.__wallBatch.stats() for scripted batch metrics. Tests cover suspension rules, hidden candidates, per-frame release, settle behavior, visibility flip re-sew, and hover not blocking settle.

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