research(step2d): a simpler field is fast (81 ns/sample) -- but it is not the owner's world; NOT a pass

Editor-only, default off (voxel.ResearchRedefinedDensityField). The redefined field is a seeded,
periodic cross-corridor pattern per strate plus the authored passages, landings and a shaft tree,
with four value-noise detail bands at every near-surface 25 cm sample and sound 8^3 brick proofs.
259^3 ring, six workers: 308 ms median (467 ms without skips) vs 8.9 s for the live field.
Detail, boundary-artefact, determinism (1 vs 6 workers, two runs) and bound-audit checks pass.

Why it is not a pass: the slices show a mostly-solid field with a few straight corridors, where the
owner's world is mostly open space; rooms, the tunnel network, composer recipes and archetypes are
gone. Much of the speed comes from 60% of bricks being proven solid in that simpler world.
What it does show: detail at full resolution plus brick skipping costs ~80-130 ns/sample; the
cost of the live field is how rooms/tunnels/passages are represented, not the detail or the lattice.

The two walkability tests were redirected to the research field in the working tree; that change
is NOT committed (saved as scratchpad step2d-test-redirect.patch) so they keep testing the live world.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01MmSoF64BbRFmk9C3p1VsBJ

CODEMAP.md

@@ -117,10 +117,12 @@ remains `0`, and lateral regions remain gated off.
 |------|------|
 | `../../VoxelForge.uplugin` | Plugin manifest. Runtime module `VoxelForge` plus the Editor-only `VoxelForgeEditor` commandlet module. Beta. |
 | `VoxelForge.Build.cs` | Deps: Core, CoreUObject, Engine, **GameplayTags**, **RealtimeMeshComponent**. |
-| `Tools/VoxelForgeTest.ps1` | The single guarded test entry point. `-Scenario canonical|owner|probe|perf|tests|surface-fall|crossing|gate-stress|visual-edit|visual-lod|visual-gap-walk|visual-gap-inject|dig-motion|parity|horizon|horizon-render|determinism|region-eval`, optional `-Build`, `-Assets owner|default`, `-Cvars`, absolute `-Out`, `-Label`, `-HorizonLevel`, `-HorizonRenderDistanceChunks`, `-ParityExportSize=32|64|128`, `-ParityExportTile=x,y,z`, `-SharedDDC`, `-SampleDensityStacks`, `-StackSampleIntervalUs`, and `-RegionHashProbe -RegionWorkers N -RegionReferenceHash HASH`; stages the host/assets, isolates user/DDC/config state, serializes one Unreal launch at a time, enforces the 8 GiB/30-minute guards, waits for 6 GiB free RAM before launches, and emits compact `result.json`/`summary.txt` plus full logs. Parity can render its game leg with `-EnableRender` and compares the selected export region against the exact streamed tile hashes. `visual-gap-walk` records camera-frustum surface-point coverage at 6000 cm/s; `visual-gap-inject` proves an early component hide is detected; `dig-motion` logs per-frame vertical velocity, gate, support readiness, and movement mode. `-Cvars @{ 'voxel.TestGapAuditLegacyHandoff'=1 }` replays the old visibility handoff for A/B audit baselines. Horizon traces report desired/loaded tiles, resident stream geometry, worker seconds, steady wall time, and peak private memory; `horizon-render` captures the owner view; `determinism` compares per-tile hashes across the default CRT path and `-voxel.CrtFma3=0`; `region-eval` compares the live path with the default-off editor chunk program on the 259³ lattice and five-seed probe set, reporting whole-ring setup/candidate counters; `-RegionHashProbe -RegionWorkers N -RegionReferenceHash HASH` checks a full-ring hash at another partition count. `-SampleDensityStacks` captures profiles, and `-StackSampleIntervalUs` sets the sampling interval.
+| `Tools/VoxelForgeTest.ps1` | The single guarded test entry point. `-Scenario canonical|owner|probe|perf|tests|surface-fall|crossing|gate-stress|visual-edit|visual-lod|visual-gap-walk|visual-gap-inject|dig-motion|parity|horizon|horizon-render|determinism|region-eval|step2d`, optional `-Build`, `-Assets owner|default`, `-Cvars`, absolute `-Out`, `-Label`, `-HorizonLevel`, `-HorizonRenderDistanceChunks`, `-ParityExportSize=32|64|128`, `-ParityExportTile=x,y,z`, `-SharedDDC`, `-SampleDensityStacks`, `-StackSampleIntervalUs`, and `-RegionHashProbe -RegionWorkers N -RegionReferenceHash HASH`; stages the host/assets, isolates user/DDC/config state, serializes one Unreal launch at a time, enforces the 8 GiB/30-minute guards, waits for 6 GiB free RAM before launches, and emits compact `result.json`/`summary.txt` plus full logs. Parity can render its game leg with `-EnableRender` and compares the selected export region against the exact streamed tile hashes. `visual-gap-walk` records camera-frustum surface-point coverage at 6000 cm/s; `visual-gap-inject` proves an early component hide is detected; `dig-motion` logs per-frame vertical velocity, gate, support readiness, and movement mode. `-Cvars @{ 'voxel.TestGapAuditLegacyHandoff'=1 }` replays the old visibility handoff for A/B audit baselines. Horizon traces report desired/loaded tiles, resident stream geometry, worker seconds, steady wall time, and peak private memory; `horizon-render` captures the owner view; `determinism` compares per-tile hashes across the default CRT path and `-voxel.CrtFma3=0`; `region-eval` compares the live path with the default-off editor chunk program on the 259³ lattice and five-seed probe set; `step2d` measures the independent full-detail research field, sound 8³ brick proofs, detail/gradient controls, slices, and worker hashes. `-RegionHashProbe -RegionWorkers N -RegionReferenceHash HASH` checks a full-ring hash at another partition count. `-SampleDensityStacks` captures profiles, and `-StackSampleIntervalUs` sets the sampling interval.
 | `Public/VoxelForgeModule.h` / `Private/VoxelForgeModule.cpp` | `FVoxelForgeModule` boilerplate (Startup/Shutdown just log). |
-| `Source/VoxelForgeEditor/VoxelForgeEditor.Build.cs` / `Private/VoxelForgeExploreCommandlet.*` | Editor/commandlet-only `-run=VoxelForgeExplore`; owns bounded render/`VF_` walk/OBJ export orchestration and is not linked by Game/Shipping. Optional `-exporttilex/y/z` sets an exact L0 tile origin for controlled export/game parity; omitting all three preserves the existing center-derived origin. `-regioneval=1` runs the default-off step-2 research harness: full-ring and five-seed Q16 comparisons, repeat hashes, shrunk-reach falsification, cold timings, full-ring setup/candidate counters, counted live fallbacks, and separate before/after stack captures when `-SampleDensityStacks` is set. `-RegionHashProbe` runs one full-ring chunk evaluation and compares its raw float hash with a reference from another worker count. |
-| `Source/VoxelForgeEditor/Private/VoxelForgeRegionEvalExperiment.*` | Lattice driver with six workers by default for the commandlet-only region experiment. The live path calls `GetDensityAt` per point; the prepared path assigns each 32³ chunk once and calls editor-only `EvaluateDensityChunk`, which seeds one block evaluation and runs canonical final-field writers across that chunk. The prepared room/SDF cache window is aligned to that chunk; 8-voxel SDF candidate bins stay editor-only and default off. Unsupported routes use counted scalar fallbacks. Full-ring output reports room/SDF cache, active-op-list, and broad-phase/index builds; general-path entries and fallbacks; candidate visits/evaluations per point; and fresh sampled attribution. The full-ring hash probe supports 1–32 fixed partitions to check determinism across worker counts. |
+| `Source/VoxelForgeEditor/VoxelForgeEditor.Build.cs` / `Private/VoxelForgeExploreCommandlet.*` | Editor/commandlet-only `-run=VoxelForgeExplore`; owns bounded render/`VF_` walk/OBJ export orchestration and is not linked by Game/Shipping. Optional `-exporttilex/y/z` sets an exact L0 tile origin for controlled export/game parity; omitting all three preserves the existing center-derived origin. `-regioneval=1` retains the exact-field step-2c research harness. `-step2d` runs the independent field benchmark without old-world equality gates and writes timing, detail, boundary, determinism, triangle, and side-by-side slice evidence under `Saved/Research/step2d`. |
+| `Source/VoxelForgeEditor/Private/VoxelForgeRegionEvalExperiment.*` | Six-worker lattice drivers for step 2c and step 2d. The original path still compares live `GetDensityAt` with the editor chunk program. Step 2d evaluates the independent field and assigns contiguous batches of 8³ bricks dynamically so surface-heavy work balances across workers. It first proves bricks uniform using a macro Lipschitz bound plus the full detail-amplitude bound; uncertain bricks retain all 25 cm detail samples. Timings split classification, point evaluation, and uniform fill; hashes compare workers 1 and 6. |
+| `Public/VoxelRedefinedDensityField.h` / `Private/VoxelRedefinedDensityField.cpp` | Default-off `WITH_EDITOR` research field, selected by `voxel.ResearchRedefinedDensityField`. A seeded connected room/corridor lattice joins authored flat passage landings; four bounded world-space value-noise bands, including a one-sample micro band, are evaluated at full resolution. Skip proofs refuse edits, passage bounds, strate boundaries, and uncertain bricks; a local derivative bound permits sound proofs through landing-floor blends. The public API adds no reflected class layout. |
+| `Private/Tests/VoxelForgeRedefinedDensityFieldTest.cpp` | Three-seed functional sweep for the research field: authored passage endpoints must bracket open air and solid floor, and each tested strate must have a walkable arrival-to-exit route. |
 | `Public/VoxelGeometryHash.h` | Header-only geometry digest shared by commandlet export and runtime tile-hash dump; hashes mesh counts and the vertex/normal/UV/color/triangle arrays with the historical CRC order. |
 | `Public/VoxelStats.h` / `Private/VoxelStats.cpp` | `stat VoxelForge` DWORD counters for tile classification, skipping, meshing, operator-stack verdicts, and cave-bail diagnosis. Each `Cave Bail *` counter names one guard; `Cave Bail No Stack` counts slots with no buildable stack (no definition, or a degenerate strate). |