perf(streaming): outer tile classifier off by default; delete mode 2

Owner-approved, on the A/B measured in 83a0e4d: the classifier plus exact validation cost more
than it saved on the game path. With it off, ready p95 is 182 vs 190-195 ms, generation p95 is
125-127 vs 139-141 ms, and density calls drop 18%.

- GVoxelForgeOuterClassifierMode defaults to 0. Mode 1 stays reachable via
  voxel.OuterClassifierMode=1 as an A/B instrument; the clamp is now 0..1.
- Mode 2 (validation samples reused as the mesher core grid) is deleted: the reuse grid,
  FVoxelMesherCoreDensityGrid, GenerateMesh's ReusableCoreGrid parameter, bValidationCoreReused,
  TotalValidationCoreReuseTiles and its log field. It could not fire: it reused the grid only
  when validation disproved a uniform verdict, which never happened, and Mixed tiles never
  validate. The mode-1 validation loop exits early again on the first disagreeing sample.
- All three GenerateMesh call sites checked; the density-count pointer binds after BandVoxHi.

Verified by Codex, checked by me against the logs:
- build ok; the measured process loaded the staged DLL, SHA-256 1024D8CF..04D
- export OBJ SHA-256 unchanged: b3e5f4c3..9b377
- a run WITHOUT the override prints outer_classifier_mode=0 validation_density_calls=0,
  proving the new default took effect
- 841/841 tiles have identical triangle counts between mode 0 and mode 1. The 394 tiles mode 1
  skipped as uniform produce 0 triangles in mode 0, so the strate band cut (applied by the
  mesher, not by validation) was not hiding geometry.

Docs: ARCHITECTURE 8.10, CODEMAP (GenerateTileResult, ClassifyTile) and fable-idea T1.d record
that streaming no longer classifies by default. WORK-NEXT item 1 records the owner's playtest:
he can no longer fall through the world.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01VZS94UH8bSsBeg5sZaxe2Y

Source/VoxelForge/Private/VoxelMarchingCubesMesher.cpp

@@ -38,7 +38,6 @@ namespace
 FVoxelMeshData UVoxelMarchingCubesMesher::GenerateMesh(FIntVector OriginVoxels, int32 Step, int32 InCellsPerAxis,
                                                        TArray<uint8>* OutCaptureGrid,
                                                        int32 BandZMinVox, int32 BandZMaxVox,
-                                                       const FVoxelMesherCoreDensityGrid* ReusableCoreGrid,
                                                        int64* OutDensitySampleCount)
 {
     TRACE_CPUPROFILER_EVENT_SCOPE(VoxelForge_MesherGenerateMesh);
@@ -230,13 +229,6 @@ FVoxelMeshData UVoxelMarchingCubesMesher::GenerateMesh(FIntVector OriginVoxels,
     const int32 CellsPerAxis = FMath::Clamp(InCellsPerAxis, 2, CHUNK_SIZE);  // coarse tiles use fewer
     const int32 GridDim      = CellsPerAxis + 1;
     const int32 MDim         = GridDim + 2;            // +1 marge de chaque côté
-    const bool bUseReusableCoreGrid = !OutCaptureGrid
-        && ReusableCoreGrid
-        && ReusableCoreGrid->OriginVoxels == OriginVoxels
-        && ReusableCoreGrid->Step == Step
-        && ReusableCoreGrid->CellsPerAxis == CellsPerAxis
-        && ReusableCoreGrid->Samples.Num() == GridDim * GridDim * GridDim;
-
     // COUPE DE CONTENU PAR STRATE — restreint le maillage (et l'échantillonnage) aux cellules
     // dont l'intervalle Z chevauche la bande [BandZMinVox, BandZMaxVox] (voxels inclusifs).
     // Les tuiles à capture ne sont jamais bandées (niveau 0 — garde-fou ci-dessous).
@@ -541,7 +533,7 @@ FVoxelMeshData UVoxelMarchingCubesMesher::GenerateMesh(FIntVector OriginVoxels,
     // gradient) sont échantillonnées — le reste du tampon reste non initialisé et non lu.
     VoxelDensityProfile::FScopedTimer MesherDensityGridTimer(
         VoxelDensityProfile::EBucket::MesherDensityGrid);
-    const bool bUseOperatorBlock = !bUseSharedDensityGrid && !bUseReusableCoreGrid
+    const bool bUseOperatorBlock = !bUseSharedDensityGrid
         && GVoxelForgeUseOperatorBlock != 0;
     if (bUseOperatorBlock)
     {
@@ -576,14 +568,6 @@ FVoxelMeshData UVoxelMarchingCubesMesher::GenerateMesh(FIntVector OriginVoxels,
                     DensityGrid[LocalIndex] = ReuseGrid->Samples[
                         (SharedZ * ReuseGrid->Dim + SharedY) * ReuseGrid->Dim + SharedX];
                 }
-                else if (bUseReusableCoreGrid
-                    && gx >= 0 && gx < GridDim
-                    && gy >= 0 && gy < GridDim
-                    && gz >= 0 && gz < GridDim)
-                {
-                    DensityGrid[LocalIndex] = ReusableCoreGrid->Samples[
-                        (gz * GridDim + gy) * GridDim + gx];
-                }
                 else
                 {
                     // World voxel = tile origin + grid offset scaled by the cell size (Step).

Source/VoxelForge/Private/VoxelWorld.cpp

@@ -82,13 +82,12 @@ namespace
         GVoxelForgeUseBlockEarlyOut,
         TEXT("Use the optional nested 8x8x8 mesher classifier in streaming."));
 
-    // Outer classifier benchmark modes: 0 = disabled, 1 = current discarded exact validation,
-    // 2 = exact validation core reused by the mesher when the candidate fails validation.
-    int32 GVoxelForgeOuterClassifierMode = 1;
+    // Outer classifier benchmark modes: 0 = disabled, 1 = current discarded exact validation.
+    int32 GVoxelForgeOuterClassifierMode = 0;
     FAutoConsoleVariableRef CVarVoxelForgeOuterClassifierMode(
         TEXT("voxel.OuterClassifierMode"),
         GVoxelForgeOuterClassifierMode,
-        TEXT("Outer tile classifier mode: 0 off, 1 discarded validation, 2 validation-core reuse."));
+        TEXT("Outer tile classifier mode: 0 off, 1 discarded exact validation."));
 
     // Startup command-line cvars can arrive before the game world has spawned AVoxelWorld (or
     // before its first tiles have become visible). Keep the diagnostic edit pending until Tick has
@@ -1058,7 +1057,6 @@ void AVoxelWorld::BeginPlay()
     TotalObsoleteWorkerTasks.store(0, std::memory_order_relaxed);
     TotalValidationDensityCalls.store(0, std::memory_order_relaxed);
     TotalMesherDensityCalls.store(0, std::memory_order_relaxed);
-    TotalValidationCoreReuseTiles.store(0, std::memory_order_relaxed);
     for (int32 LOD = 0; LOD < TrackedClassifierLODCount; ++LOD)
     {
         OuterClassifierCallsByLOD[LOD].store(0, std::memory_order_relaxed);
@@ -1098,7 +1096,7 @@ void AVoxelWorld::BeginPlay()
         GVoxelForgeOuterClassifierMode = CommandLineOuterClassifierMode;
     }
     GVoxelForgeUseBlockEarlyOut = GVoxelForgeUseBlockEarlyOut != 0 ? 1 : 0;
-    GVoxelForgeOuterClassifierMode = FMath::Clamp(GVoxelForgeOuterClassifierMode, 0, 2);
+    GVoxelForgeOuterClassifierMode = FMath::Clamp(GVoxelForgeOuterClassifierMode, 0, 1);
 
     if (GVoxelForgePerfAttribution != 0)
     {
@@ -2181,7 +2179,6 @@ void AVoxelWorld::LogStreamingLatencySummary() const
              "outer_classifier_mode=%d nested_block_early_out=%d "
              "worker_generation_tasks=%llu worker_generation_sum_s=%.6f "
              "validation_density_calls=%llu mesher_density_calls=%llu "
-             "validation_core_reuse_tiles=%llu "
              "obsolete_worker_tasks=%llu obsolete_worker_sum_s=%.6f "
              "outer_classifier_verdicts=%s"),
         bDiagnosticsEnabled ? TEXT("profiled") : TEXT("clean"),
@@ -2197,7 +2194,6 @@ void AVoxelWorld::LogStreamingLatencySummary() const
         FPlatformTime::ToSeconds64(WorkerGenerationCycles),
         static_cast<unsigned long long>(TotalValidationDensityCalls.load(std::memory_order_relaxed)),
         static_cast<unsigned long long>(TotalMesherDensityCalls.load(std::memory_order_relaxed)),
-        static_cast<unsigned long long>(TotalValidationCoreReuseTiles.load(std::memory_order_relaxed)),
         static_cast<unsigned long long>(TotalObsoleteWorkerTasks.load(std::memory_order_relaxed)),
         FPlatformTime::ToSeconds64(ObsoleteWorkerCycles),
         *ClassifierVerdictSummary);
@@ -3885,7 +3881,6 @@ void AVoxelWorld::GenerateTileResult(const FVoxelTileKey& Tile, const FIntVector
     Result.NumTriangles = 0;
     Result.ValidationDensityCalls = 0;
     Result.MesherDensityCalls = 0;
-    Result.bValidationCoreReused = false;
     Result.Streams.Reset();
     Result.CaptureGrid.Reset();
     Result.BandChunkLo = BandChunkLo;   // strate content cut (MIN/MAX = uncut)
@@ -3917,10 +3912,7 @@ void AVoxelWorld::GenerateTileResult(const FVoxelTileKey& Tile, const FIntVector
     // même pour les cellules uniformes, et ces tuiles sont rares (fenêtre d'ombre).
     // (Gate IsoLevel == 0 : les verdicts du classifieur supposent l'iso MC à zéro exactement.)
     bool bTrivialEmpty = false;
-    FVoxelMesherCoreDensityGrid ValidationCoreGrid;
-    const FVoxelMesherCoreDensityGrid* ReusableCoreGrid = nullptr;
-    const int32 OuterClassifierMode = FMath::Clamp(GVoxelForgeOuterClassifierMode, 0, 2);
-    const bool bUseValidationCoreReuse = OuterClassifierMode == 2;
+    const int32 OuterClassifierMode = FMath::Clamp(GVoxelForgeOuterClassifierMode, 0, 1);
     if (OuterClassifierMode != 0
         && !bSheetTile && !bWantCapture && Generator && Mesher && Mesher->IsoLevel == 0.0f)
     {
@@ -3950,19 +3942,9 @@ void AVoxelWorld::GenerateTileResult(const FVoxelTileKey& Tile, const FIntVector
             TGuardValue<int32> ValidationSampleStepGuard(
                 VoxelGenLOD::SampleStep, ValidationStep);
 
-            if (bUseValidationCoreReuse)
-            {
-                ValidationCoreGrid.OriginVoxels = OriginVoxels;
-                ValidationCoreGrid.Step = ValidationStep;
-                ValidationCoreGrid.CellsPerAxis = ValidationCells;
-                const int32 ValidationDim = ValidationCells + 1;
-                ValidationCoreGrid.Samples.SetNumUninitialized(
-                    ValidationDim * ValidationDim * ValidationDim);
-            }
-
             bool bExactUniform = true;
             for (int32 Z = 0; Z <= ValidationCells
-                && (bUseValidationCoreReuse || bExactUniform) && !bValidationAborted; ++Z)
+                && bExactUniform && !bValidationAborted; ++Z)
             {
                 if (ShouldAbortWork(ObsoleteFlag))
                 {
@@ -3970,7 +3952,7 @@ void AVoxelWorld::GenerateTileResult(const FVoxelTileKey& Tile, const FIntVector
                     break;
                 }
                 for (int32 Y = 0; Y <= ValidationCells
-                    && (bUseValidationCoreReuse || bExactUniform) && !bValidationAborted; ++Y)
+                    && bExactUniform && !bValidationAborted; ++Y)
                 {
                     for (int32 X = 0; X <= ValidationCells; ++X)
                     {
@@ -3984,22 +3966,13 @@ void AVoxelWorld::GenerateTileResult(const FVoxelTileKey& Tile, const FIntVector
                             OriginVoxels.Y + Y * ValidationStep,
                             OriginVoxels.Z + Z * ValidationStep);
                         ++Result.ValidationDensityCalls;
-                        if (bUseValidationCoreReuse)
-                        {
-                            const int32 ValidationDim = ValidationCells + 1;
-                            ValidationCoreGrid.Samples[
-                                (Z * ValidationDim + Y) * ValidationDim + X] = Density;
-                        }
                         const bool bSampleAgrees = FMath::IsFinite(Density) && Density != 0.0f
                             && (Verdict != EVoxelTileClass::AllSolid || Density < 0.0f)
                             && (Verdict != EVoxelTileClass::AllAir || Density > 0.0f);
                         if (!bSampleAgrees)
                         {
                             bExactUniform = false;
-                            if (!bUseValidationCoreReuse)
-                            {
-                                break;
-                            }
+                            break;
                         }
                     }
                 }
@@ -4011,12 +3984,6 @@ void AVoxelWorld::GenerateTileResult(const FVoxelTileKey& Tile, const FIntVector
                 // A false Mixed costs meshing; a false uniform verdict removes both render and
                 // collision geometry. Fall back to the safe path whenever one exact vertex disagrees.
                 ValidatedVerdict = EVoxelTileClass::Mixed;
-                if (bUseValidationCoreReuse && !bValidationAborted)
-                {
-                    ReusableCoreGrid = &ValidationCoreGrid;
-                    Result.bValidationCoreReused = true;
-                    TotalValidationCoreReuseTiles.fetch_add(1, std::memory_order_relaxed);
-                }
             }
         }
         if (bValidationAborted)
@@ -4067,7 +4034,7 @@ void AVoxelWorld::GenerateTileResult(const FVoxelTileKey& Tile, const FIntVector
                                         HoleMinX, HoleMinY, HoleMaxX, HoleMaxY)
             : Mesher->GenerateMesh(OriginVoxels, Step, Cells,
                                    bWantCapture ? &Result.CaptureGrid : nullptr,
-                                   BandVoxLo, BandVoxHi, ReusableCoreGrid,
+                                   BandVoxLo, BandVoxHi,
                                    &Result.MesherDensityCalls);
         TotalMesherDensityCalls.fetch_add(
             static_cast<uint64>(Result.MesherDensityCalls), std::memory_order_relaxed);

Source/VoxelForge/Public/VoxelMarchingCubesMesher.h

@@ -38,8 +38,6 @@ struct FVoxelSharedDensityGrid
     }
 };
 
-struct FVoxelMesherCoreDensityGrid;
-
 UCLASS(BlueprintType)
 class VOXELFORGE_API UVoxelMarchingCubesMesher : public UObject
 {
@@ -72,7 +70,6 @@ public:
     FVoxelMeshData GenerateMesh(FIntVector OriginVoxels, int32 Step = 1, int32 CellsPerAxis = CHUNK_SIZE,
                                 TArray<uint8>* OutCaptureGrid = nullptr,
                                 int32 BandZMinVox = INT32_MIN, int32 BandZMaxVox = INT32_MAX,
-                                const FVoxelMesherCoreDensityGrid* ReusableCoreGrid = nullptr,
                                 int64* OutDensitySampleCount = nullptr);
 
     /**
@@ -166,22 +163,3 @@ public:
     // Réduction d'octaves sur les tuiles grossières ; 0 = désactivé.
     int32 LODOctaveDrop = 0;
 };
-
-// A per-tile core lattice produced by the outer classifier's exact validation.  Unlike
-// FVoxelSharedDensityGrid this is intentionally local to one GenerateMesh call: validation can
-// run concurrently on several streaming workers without mutating shared mesher state.
-struct FVoxelMesherCoreDensityGrid
-{
-    FIntVector OriginVoxels = FIntVector::ZeroValue;
-    int32 Step = 1;
-    int32 CellsPerAxis = 0;
-    TArray<float> Samples;
-
-    void Reset()
-    {
-        OriginVoxels = FIntVector::ZeroValue;
-        Step = 1;
-        CellsPerAxis = 0;
-        Samples.Reset();
-    }
-};

Source/VoxelForge/Public/VoxelWorld.h

@@ -111,7 +111,6 @@ struct FChunkResult
     // count exact validation and mesher density calls locally, then publish one aggregate update.
     int64 ValidationDensityCalls = 0;
     int64 MesherDensityCalls = 0;
-    bool bValidationCoreReused = false;
     bool bAborted = false;    // Worker observed shutdown or cancellation; never mark this tile loaded
     bool bObsolete = false;   // Worker observed per-tile desired-set cancellation
     uint32 DesiredEpoch = 0;  // Desired-set epoch captured at request time
@@ -929,7 +928,6 @@ public:
     std::atomic<uint64> TotalObsoleteWorkerTasks{0};
     std::atomic<uint64> TotalValidationDensityCalls{0};
     std::atomic<uint64> TotalMesherDensityCalls{0};
-    std::atomic<uint64> TotalValidationCoreReuseTiles{0};
     std::atomic<uint64> OuterClassifierCallsByLOD[TrackedClassifierLODCount]{};
     std::atomic<uint64> OuterClassifierVerdictsByLOD[TrackedClassifierLODCount][3]{};