VoxelForge/Standalone/Research/WorldAssemblerM3/Astra3/REVIEW.md

[INFERENCE] Improve the existing brick-proof system; don’t add a general “checked voxel” mask. The promising savings are avoided field/composition work and passage preparation, rather than marching-cubes classification.

References below abbreviate these files: M = production mesher, S = ShapeWorldInternal.h, C = VoxelForgeCore.cpp, O = VoxelDensityOpStack.cpp. L-numbers identify Standalone/Research/WorldAssemblerM3/LinuxN/REPORT.md.

[INFERENCE] Evidence limitation: Linux128 is absent from this checkout. Its supplied 7.9 m support and slower one-owner result remain unverified here. The reports below span different revisions; their percentages must not be presented as today’s census.

1. Where time goes

[MEASURED] L77’s exclusive FI/TN LOD0–2 worker account:

Work	FI	TN
Total worker CPU/view	23.02 s	21.50 s
Passage composition	65.9%	65.4%
Support	14.2%	13.5%
Base field	3.2%	3.3%
Bands / dispatch	2.3% / 3.7%	2.6% / 3.6%
MC / skirts / refinement, excluding field work	1.6% / 0.1% / 7.5%	1.2% / 0.2% / 8.6%

[MEASURED] Grid fill occupied 19.058/17.377 worker-seconds, overlapping those phase categories. L117’s later census found support zero; its smooth-tunnel regression concentrated about 95% of added tile CPU in passage-feature tiles. Cell classification stayed flat; gradients became cheaper. Thus L77 identifies historical leverage, not current percentages.

[MEASURED] L125 preparation averaged 514/130/4.1 ms worker work at LOD0/1/2. LOD0 evaluated 3.11–8.49 million segment/sample pairs with 67–72% overlap, although the exact band occupied only 5–7% of grid samples. L126 reduced floor-profile calls 20–23% without useful readiness improvement.

[CODE] Brick skipping already exists: configurable block verdicts, required-sample masks, and active-block gradient halos (M:646,1053). MC already rejects cells without sign crossings before interpolation/gradients (M:2186). Gradient memoisation exists (M:1956). Skirts issue separate density queries (M:2491); refinement has its own stage (C:2975).

[INFERENCE] A pre-evaluation proof can save density, composition, and subsequent MC work. A sign mask constructed after density evaluation saves only downstream scanning. Classification itself costs work; no isolated current classification percentage is established by these reports.

[MEASURED] L124’s shape gate alone took 179–226 ms, with no near-tile admissions before completion. L87 additionally measured a 107–153 ms far-parent gate and no headless collision wait. Tile masks cannot directly remove these gates or explain the supplied UE/headless gap.

2. Sound flags and hazards

[INFERENCE] For final density (D), solid requires an upper bound covering the evaluator’s supremum, (U<0); air requires a valid lower bound (L\ge0). “Deep” requires an explicit margin. Unknown must stay unknown. A crossing proves an MC-active cell; uniform sampled signs do not prove an entire continuous volume surface-free.

[CODE] Reusable proofs include:

• S:5428: halo-expanded box classification.
• S:5974: exact surface-column extrema over the MC lattice.
• S:6019: floating-island density intervals.
• S:5197,6032: native cave intervals.
• S:5949: stamp interval composition with outward numerical padding.
• O:6998: operation-specific inactivity from SDF lower bounds.

[CODE] These proofs have guards: passage overlap returns unknown (S:5687); unsupported stamp composition returns unknown (S:5655); stratum crossings are rejected (S:5900). The mesher distinguishes uniform candidates from bSkipSafe certificates (M:715,756), and otherwise validates candidates against actual samples (M:1838).

[CODE] For gated modifiers, Identity can mean Sdf >= T, not abs(Sdf) >= T (O:1496,6998). Noise bounds cannot assume nominal [-1,1]: FBM and unclamped cellular bounds are explicitly discussed at O:848,301.

[INFERENCE] Additional hazards: confusing internal SDF with final density; certifying base terrain before caves, tunnels, shells, stamps or edits; using lattice proofs for off-grid queries; ignoring rounding or gradient halos. A below-TerrainZ solid rule applied to 3D caves deletes caves. “Touched by tunnel” should mean conservative candidate overlap; only proven untouched authorizes omission.

3. Granularity

[INFERENCE] Storage per flag for 32³ cells:

Granularity	Storage	Construction/tradeoff
Per cell	4 KiB	32,768 decisions; expensive unless derived during necessary work
4³ bricks	64 B	512 proofs; tighter boundaries, more proof/halo overhead
8³ bricks	8 B	64 proofs; cheaper, more mixed bricks
XY columns	128 B	1,024 decisions; useful mainly for heightfield-specific proofs

[INFERENCE] These exclude corner/halo samples, metadata and additional flags. A column bit cannot represent multiple cave intervals. Brick runs preserve contiguous X sampling and SIMD better than scattered per-sample branches; bit packing alone does not establish a speedup.

[CODE] The existing implementation uses byte arrays and preserves exact samples around active bricks (M:1053–1083). Replacing densities with arbitrary same-sign constants near active cells would corrupt interpolated positions or normals.

4. “Already evaluated”

[CODE] Passage preparation precedes meshing (C:2747). Its valid sentinel is initialization, not completion: subsequent segments update floor selection, shell minima and round-distance winners, with deterministic tie-breaking (S:11520,11615,11688).

[INFERENCE] Therefore first-visitor wins is invalid. Memoisation is valid only for identical queries against identical seed/layout/evaluator/edit revision and query semantics; cache the value, not just a bit.

[MEASURED] L77 counted 8.6–8.9% halo points, without measuring duplicate coordinates. L125 verified 4,900 shared samples across four neighbour pairs and still recorded substantial off-grid skirt/midpoint fallbacks.

[CODE] Shared-grid reuse and gradient validity caches already exist (M:1031,1956). [INFERENCE] Skirt/seam queries are reuse candidates only when coordinates and semantics actually match; “same voxel” is insufficient.

5. Other uses

[INFERENCE] Edit-dirty bricks can localize regeneration, with invalidation expanded through normals, seams and collision dependencies. Collision-only servers can skip certified empty regions, but still need boundary geometry. Streaming can prioritize potentially occupied bricks; nav and lighting need clearance/connectivity or visibility data beyond occupancy. Keep masks derived locally from replicated seed + layout + diff, versioned with that state.

6. Recommendation

• [INFERENCE] Tune existing 4³/8³ certificates, caching proofs and emitting contiguous required-sample runs. Plausible incremental near-ready saving: 0–5%, with regressions possible. Measure proof time, samples avoided, halo expansion, total worker CPU and UE readiness.
• [INFERENCE] Pass required-region information into passage preparation, rejecting whole segment/brick regions conservatively. Plausible near-ready saving: 0–10%, highly uncertain because passage overlap currently vetoes proofs. Kill it if pair reduction fails to reduce preparation and end-to-end time.

[INFERENCE] Both require seam/off-grid validation, adversarial bound checks, edit invalidation tests, and cross-machine/worker determinism. Preserve canonical tie-breaking; old-version byte identity need not constrain a sound redesign.