perf(generation): per-tile reach test skips landing and structural posts -- ~12% less worker CPU

The remove-one ablation put landing posts at ~10% and passage structural posts at ~6% of worker
time, though landings exist only near passage ends and the origin. The parked exact-cull round's
per-SAMPLE post bounds had been a net loss. This round decides reach once per TILE (Codex;
reviewed by me).

- VoxelTilePostReach.h: one per-tile reach mask (thread-local byte), set when the tile is set
  up. The origin landing, passage landing SDF/floors, native floors, tunnel air and passage
  structural posts return their input unchanged on tiles no instance can reach. Per sample this
  costs an inline flag read.
- Reach proofs come from each post's geometry (origin rooms, landing SDF and floors, native floor
  band, structural support spheres), not from comments.
- voxel.TilePostReachDebug=1 evaluates the skipped posts anyway and compares the FINAL field;
  voxel.TilePostReachScale=0.5 deliberately shrinks the reach and must fail.

Default build: 694 tiles, landing reachable on 4 (skipped on 690), structural posts skipped on 169.
Soundness: 123,958,673 comparisons, 0 differences; shrunk reach: 13,929 differences, FAIL as
required.

Final DEFAULT build vs the committed-tip DLL (same command line, two interleaved runs each):
  static  worker 34.80 -> 30.52 s (-12%)   LOD0 generation p50/p95 67.0/107.6 -> 55.8/95.8 ms
  moving  worker 75.96 -> 66.66 s (-12%)   LOD0 generation p50/p95 66.3/106.0 -> 56.0/95.8 ms
Field exact: 841/841 keyed tiles vs a fresh committed-tip trace (669,902 triangles, which includes
9260775's gap floors), export b3e5f4c3..9b377, capability 20,830 / 10,909; strate-crossing and
sealed-proof tests pass.
Ledger: all launches passed or failed where designed to; early raw-SDF debug attempts failed
until the comparator was corrected to compare the final field. No crash folders.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01TaFdXhTdYMkW1xrV6ApT6Y

Source/VoxelForge/Private/VoxelMarchingCubesMesher.cpp

@@ -4,6 +4,8 @@
 #include "VoxelMarchingCubesMesher.h"
 #include "MarchingCubesTables.h"
 #include "VoxelDensityProfile.h"
+#include "VoxelStrateManager.h"
+#include "VoxelTilePostReach.h"
 #include "ProfilingDebugging/CpuProfilerTrace.h"
 #include "HAL/IConsoleManager.h"
 #include "Misc/CommandLine.h"
@@ -17,6 +19,45 @@ namespace
         TEXT("Use the operator-major density block path for non-shared mesher grids."));
     bool GVoxelForgeBlockSwitchParsed = false;
 
+    int32 GVoxelForgeTilePostReachDebug = 0;
+    FAutoConsoleVariableRef CVarVoxelForgeTilePostReachDebug(
+        TEXT("voxel.TilePostReachDebug"),
+        GVoxelForgeTilePostReachDebug,
+        TEXT("Run skipped landing/structural posts in a bypass and compare their exact result; "
+             "a nonzero difference fails the debug run."));
+
+    float GVoxelForgeTilePostReachScale = 1.0f;
+    FAutoConsoleVariableRef CVarVoxelForgeTilePostReachScale(
+        TEXT("voxel.TilePostReachScale"),
+        GVoxelForgeTilePostReachScale,
+        TEXT("Scale the per-tile post reach for deliberate soundness tests. Default 1.0 is exact; "
+             "values below 1 intentionally shrink the guard."));
+
+    bool GVoxelForgeTilePostReachSwitchesParsed = false;
+
+    void VF_ParseTilePostReachSwitches()
+    {
+        if (GVoxelForgeTilePostReachSwitchesParsed)
+        {
+            return;
+        }
+        GVoxelForgeTilePostReachSwitchesParsed = true;
+        int32 DebugValue = GVoxelForgeTilePostReachDebug;
+        float ScaleValue = GVoxelForgeTilePostReachScale;
+        FParse::Value(
+            FCommandLine::Get(), TEXT("voxel.TilePostReachDebug="), DebugValue);
+        FParse::Value(
+            FCommandLine::Get(), TEXT("voxel.TilePostReachScale="), ScaleValue);
+        GVoxelForgeTilePostReachDebug = DebugValue != 0 ? 1 : 0;
+        if (!VoxelMath::IsFinite(ScaleValue) || ScaleValue <= 0.0f)
+        {
+            ScaleValue = 1.0f;
+        }
+        GVoxelForgeTilePostReachScale = FMath::Min(ScaleValue, 1.0f);
+        VoxelGenLOD::GTilePostReachDebugEnabled.store(
+            GVoxelForgeTilePostReachDebug != 0, std::memory_order_relaxed);
+    }
+
     void VF_ParseOperatorBlockSwitch()
     {
         if (GVoxelForgeBlockSwitchParsed) { return; }
@@ -42,6 +83,7 @@ FVoxelMeshData UVoxelMarchingCubesMesher::GenerateMesh(FIntVector OriginVoxels,
 {
     TRACE_CPUPROFILER_EVENT_SCOPE(VoxelForge_MesherGenerateMesh);
     VF_ParseOperatorBlockSwitch();
+    VF_ParseTilePostReachSwitches();
     FVoxelMeshData MeshData;
     if (OutCaptureGrid) { OutCaptureGrid->Reset(); }
     if (OutDensitySampleCount) { *OutDensitySampleCount = 0; }
@@ -233,6 +275,49 @@ FVoxelMeshData UVoxelMarchingCubesMesher::GenerateMesh(FIntVector OriginVoxels,
         VoxelGenLOD::TileOriginVoxels, OriginVoxels);
     TGuardValue<int32> TileCellsGuard(
         VoxelGenLOD::TileCellsPerAxis, CellsPerAxis);
+
+    // Every density sample in this tile sees the same post-reach decision.  The one-point halo
+    // matches the actual grid fill below (gx/gy/gz = -1..GridDim), so a false bit proves that no
+    // landing or passage structural writer can reach any sample used by meshing or gradients.
+    TGuardValue<bool> TilePostReachDebugGuard(
+        VoxelGenLOD::bTilePostReachDebug,
+        GVoxelForgeTilePostReachDebug != 0);
+    TGuardValue<bool> TilePostReachBypassGuard(
+        VoxelGenLOD::bTilePostReachBypass, false);
+    uint8 TilePostReachFlags = VoxelGenLOD::AllTilePostReach;
+    if (Generator->StrateManager != nullptr)
+    {
+        const int64 Extent = static_cast<int64>(CellsPerAxis + 1) * Step;
+        const FBox LatticeWithHalo(
+            FVector(
+                static_cast<float>(static_cast<int64>(OriginVoxels.X) - Step),
+                static_cast<float>(static_cast<int64>(OriginVoxels.Y) - Step),
+                static_cast<float>(static_cast<int64>(OriginVoxels.Z) - Step)),
+            FVector(
+                static_cast<float>(static_cast<int64>(OriginVoxels.X) + Extent),
+                static_cast<float>(static_cast<int64>(OriginVoxels.Y) + Extent),
+                static_cast<float>(static_cast<int64>(OriginVoxels.Z) + Extent)));
+        const float ReachScale = GVoxelForgeTilePostReachScale;
+        TilePostReachFlags = 0;
+        if (Generator->StrateManager->AnyOriginLandingNearLattice(
+                LatticeWithHalo, OriginVoxels, Step, ReachScale))
+        {
+            TilePostReachFlags |= VoxelGenLOD::OriginLandingReachable;
+        }
+        if (Generator->StrateManager->AnyPassageLandingNearLattice(
+                LatticeWithHalo, OriginVoxels, Step, ReachScale))
+        {
+            TilePostReachFlags |= VoxelGenLOD::PassageLandingReachable;
+        }
+        if (Generator->StrateManager->AnyPassageStructuralPostNearLattice(
+                LatticeWithHalo, OriginVoxels, Step, ReachScale))
+        {
+            TilePostReachFlags |= VoxelGenLOD::PassageStructuralReachable;
+        }
+    }
+    TGuardValue<uint8> TilePostReachFlagsGuard(
+        VoxelGenLOD::TilePostReachFlags, TilePostReachFlags);
+    VoxelGenLOD::RecordTileReachMask(TilePostReachFlags);
     // 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).

Source/VoxelForge/Private/VoxelStrateManager.cpp

@@ -2511,6 +2511,12 @@ float UVoxelStrateManager::EvaluateModifierSDF(float WorldX, float WorldY, float
         return FLT_MAX;
     }
 
+    // The landing terms are part of the passage modifier, so their reach proof is deliberately
+    // wider than the direct post's four-voxel blend: SmoothMin can lower a finite term by K/6 at
+    // each later combine.  Outside that padded room domain, omitting the two landing evaluations
+    // is an identity for VF_ApplyPassageCarving.
+    const bool bEvaluateLandingSDF = VoxelGenLOD::IsPassageLandingReachable()
+        || VoxelGenLOD::IsTilePostReachBypassActive();
     const FIntVector ChunkCoord(
         FMath::FloorToInt(WorldX / (float)CHUNK_SIZE),
         FMath::FloorToInt(WorldY / (float)CHUNK_SIZE),
@@ -2602,10 +2608,13 @@ float UVoxelStrateManager::EvaluateModifierSDF(float WorldX, float WorldY, float
         // A landing is a real room with a hard flat-floor half-space, not a sphere around the
         // tube endpoint. It is the same fixed SDF geometry selected during GeneratePassages; it
         // never performs a source query here and does not synthesize a radial root connector.
-        const float UpperLandingSDF = VF_EvaluatePassageLandingSDF(Pos, P.UpperLanding);
-        const float LowerLandingSDF = VF_EvaluatePassageLandingSDF(Pos, P.LowerLanding);
-        MinSDF = VoxelSDF::SmoothMin(MinSDF, UpperLandingSDF, BlendK);
-        MinSDF = VoxelSDF::SmoothMin(MinSDF, LowerLandingSDF, BlendK);
+        if (bEvaluateLandingSDF)
+        {
+            const float UpperLandingSDF = VF_EvaluatePassageLandingSDF(Pos, P.UpperLanding);
+            const float LowerLandingSDF = VF_EvaluatePassageLandingSDF(Pos, P.LowerLanding);
+            MinSDF = VoxelSDF::SmoothMin(MinSDF, UpperLandingSDF, BlendK);
+            MinSDF = VoxelSDF::SmoothMin(MinSDF, LowerLandingSDF, BlendK);
+        }
     }
 
     return MinSDF;
@@ -2617,13 +2626,41 @@ void UVoxelStrateManager::ApplyPassageModifier(
 {
     VoxelDensityProfile::FScopedTimer ProfileTimer(
         VoxelDensityProfile::EBucket::PassageModifier);
+    const bool bBypass = VoxelGenLOD::IsTilePostReachBypassActive();
+    const bool bCompareLandingModifier = VoxelGenLOD::bTilePostReachDebug
+        && !VoxelGenLOD::IsPassageLandingReachable() && !bBypass;
+    float CanonicalModifierDensity = Density;
+    if (bCompareLandingModifier)
+    {
+        const bool PreviousBypass = VoxelGenLOD::bTilePostReachBypass;
+        VoxelGenLOD::bTilePostReachBypass = true;
+        const float CanonicalSDF = EvaluateModifierSDF(WorldX, WorldY, WorldZ);
+        VF_ApplyPassageCarving(
+            CanonicalModifierDensity, CanonicalSDF, BaseDensity, SealThickness);
+        VoxelGenLOD::bTilePostReachBypass = PreviousBypass;
+    }
     if (!VoxelDensityAblation::IsPassageCarvingOff())
     {
         const float ModSDF = EvaluateModifierSDF(WorldX, WorldY, WorldZ);
         VF_ApplyPassageCarving(Density, ModSDF, BaseDensity, SealThickness);
     }
+    if (bCompareLandingModifier)
+    {
+        VoxelGenLOD::RecordSkippedPostComparison(
+            VoxelGenLOD::ETilePostComparisonKind::PassageLandingSDF,
+            !VoxelGenLOD::SameFloatBits(Density, CanonicalModifierDensity));
+    }
     ApplyPassageLandingAir(Density, WorldX, WorldY, WorldZ, BaseDensity, SealThickness);
 
+    const bool bLandingReachable = VoxelGenLOD::IsPassageLandingReachable()
+        || VoxelGenLOD::IsTilePostReachBypassActive();
+    const bool bStructuralReachable = VoxelGenLOD::IsPassageStructuralReachable()
+        || VoxelGenLOD::IsTilePostReachBypassActive();
+    if (!bLandingReachable && !bStructuralReachable)
+    {
+        return;
+    }
+
     const FIntVector ChunkCoord(
         FMath::FloorToInt(WorldX / (float)CHUNK_SIZE),
         FMath::FloorToInt(WorldY / (float)CHUNK_SIZE),
@@ -2634,10 +2671,12 @@ void UVoxelStrateManager::ApplyPassageModifier(
     for (const int32 PassageIndex : Nearby)
     {
         const FVoxelPassage& Passage = PassageData[PassageIndex];
-        const bool bLandingFloor = !VoxelDensityAblation::IsLandingPostsOff()
+        const bool bLandingFloor = bLandingReachable
+            && !VoxelDensityAblation::IsLandingPostsOff()
             && (VF_IsPassageLandingFloor(Position, Passage.UpperLanding)
                 || VF_IsPassageLandingFloor(Position, Passage.LowerLanding));
-        const bool bLegacySupportFloor = !VoxelDensityAblation::IsPassageStructuralPostsOff()
+        const bool bLegacySupportFloor = bStructuralReachable
+            && !VoxelDensityAblation::IsPassageStructuralPostsOff()
             && bPassageSupportFloorWritesEnabled
             && !Passage.bNativeFloorEnabled
             && VF_IsWalkableTunnelFloor(Passage, Position, this, PassageIndex);
@@ -2656,7 +2695,10 @@ void UVoxelStrateManager::ApplyPassageModifier(
     // the current walkable tunnel.  Reassert tunnel air after all floor posts so overlap cannot
     // turn a valid route into a solid plug.  At the tunnel's own floor the air predicate is false,
     // so the support plane remains solid.
-    ApplyPassageTunnelAir(Density, WorldX, WorldY, WorldZ, BaseDensity, SealThickness);
+    if (bStructuralReachable)
+    {
+        ApplyPassageTunnelAir(Density, WorldX, WorldY, WorldZ, BaseDensity, SealThickness);
+    }
 }
 
 void UVoxelStrateManager::ApplyPassageCarvingOnly(
@@ -2669,8 +2711,27 @@ void UVoxelStrateManager::ApplyPassageCarvingOnly(
     }
     VoxelDensityProfile::FScopedTimer ProfileTimer(
         VoxelDensityProfile::EBucket::PassageModifier);
+    const bool bBypass = VoxelGenLOD::IsTilePostReachBypassActive();
+    const bool bCompareLandingModifier = VoxelGenLOD::bTilePostReachDebug
+        && !VoxelGenLOD::IsPassageLandingReachable() && !bBypass;
+    float CanonicalModifierDensity = Density;
+    if (bCompareLandingModifier)
+    {
+        const bool PreviousBypass = VoxelGenLOD::bTilePostReachBypass;
+        VoxelGenLOD::bTilePostReachBypass = true;
+        const float CanonicalSDF = EvaluateModifierSDF(WorldX, WorldY, WorldZ);
+        VF_ApplyPassageCarving(
+            CanonicalModifierDensity, CanonicalSDF, BaseDensity, SealThickness);
+        VoxelGenLOD::bTilePostReachBypass = PreviousBypass;
+    }
     const float ModSDF = EvaluateModifierSDF(WorldX, WorldY, WorldZ);
     VF_ApplyPassageCarving(Density, ModSDF, BaseDensity, SealThickness);
+    if (bCompareLandingModifier)
+    {
+        VoxelGenLOD::RecordSkippedPostComparison(
+            VoxelGenLOD::ETilePostComparisonKind::PassageLandingSDF,
+            !VoxelGenLOD::SameFloatBits(Density, CanonicalModifierDensity));
+    }
 }
 
 void UVoxelStrateManager::ApplyPassageLandingAir(
@@ -2681,6 +2742,16 @@ void UVoxelStrateManager::ApplyPassageLandingAir(
     {
         return;
     }
+    if (!VoxelGenLOD::IsPassageLandingReachable()
+        && !VoxelGenLOD::IsTilePostReachBypassActive())
+    {
+        VoxelGenLOD::CompareSkippedPost(Density, [&]()
+        {
+            ApplyPassageLandingAir(
+                Density, WorldX, WorldY, WorldZ, BaseDensity, SealThickness);
+        }, VoxelGenLOD::ETilePostComparisonKind::PassageLandingAir);
+        return;
+    }
     VoxelDensityProfile::FScopedTimer ProfileTimer(
         VoxelDensityProfile::EBucket::PassageLandingAir);
     const FIntVector ChunkCoord(
@@ -2749,6 +2820,16 @@ void UVoxelStrateManager::ApplyPassageTunnelAir(
     {
         return;
     }
+    if (!VoxelGenLOD::IsPassageStructuralReachable()
+        && !VoxelGenLOD::IsTilePostReachBypassActive())
+    {
+        VoxelGenLOD::CompareSkippedPost(Density, [&]()
+        {
+            ApplyPassageTunnelAir(
+                Density, WorldX, WorldY, WorldZ, BaseDensity, SealThickness);
+        }, VoxelGenLOD::ETilePostComparisonKind::PassageTunnelAir);
+        return;
+    }
     VoxelDensityProfile::FScopedTimer ProfileTimer(
         VoxelDensityProfile::EBucket::PassageTunnelAir);
     const FVector Position(WorldX, WorldY, WorldZ);
@@ -2784,6 +2865,30 @@ void UVoxelStrateManager::ApplyPassageLandingFloorMC(
     {
         return;
     }
+    const bool bBypass = VoxelGenLOD::IsTilePostReachBypassActive();
+    const bool bLandingReachable = VoxelGenLOD::IsPassageLandingReachable() || bBypass;
+    const bool bStructuralReachable = VoxelGenLOD::IsPassageStructuralReachable() || bBypass;
+    const bool bCompareLanding = VoxelGenLOD::bTilePostReachDebug
+        && !bLandingReachable && !bBypass;
+    float CanonicalDensity = Density;
+    if (bCompareLanding)
+    {
+        const bool PreviousBypass = VoxelGenLOD::bTilePostReachBypass;
+        VoxelGenLOD::bTilePostReachBypass = true;
+        ApplyPassageLandingFloorMC(
+            CanonicalDensity, WorldX, WorldY, WorldZ, BaseDensity);
+        VoxelGenLOD::bTilePostReachBypass = PreviousBypass;
+    }
+    if (!bLandingReachable && !bStructuralReachable)
+    {
+        if (bCompareLanding)
+        {
+            VoxelGenLOD::RecordSkippedPostComparison(
+                VoxelGenLOD::ETilePostComparisonKind::PassageLandingFloor,
+                !VoxelGenLOD::SameFloatBits(Density, CanonicalDensity));
+        }
+        return;
+    }
     VoxelDensityProfile::FScopedTimer ProfileTimer(
         VoxelDensityProfile::EBucket::PassageLandingFloor);
     const FIntVector ChunkCoord(
@@ -2796,10 +2901,12 @@ void UVoxelStrateManager::ApplyPassageLandingFloorMC(
     for (const int32 PassageIndex : Nearby)
     {
         const FVoxelPassage& Passage = PassageData[PassageIndex];
-        const bool bLandingFloor = !VoxelDensityAblation::IsLandingPostsOff()
+        const bool bLandingFloor = bLandingReachable
+            && !VoxelDensityAblation::IsLandingPostsOff()
             && (VF_IsPassageLandingFloor(Position, Passage.UpperLanding)
                 || VF_IsPassageLandingFloor(Position, Passage.LowerLanding));
-        const bool bLegacySupportFloor = !VoxelDensityAblation::IsPassageStructuralPostsOff()
+        const bool bLegacySupportFloor = bStructuralReachable
+            && !VoxelDensityAblation::IsPassageStructuralPostsOff()
             && bPassageSupportFloorWritesEnabled
             && !Passage.bNativeFloorEnabled
             && VF_IsWalkableTunnelFloor(Passage, Position, this, PassageIndex);
@@ -2812,6 +2919,12 @@ void UVoxelStrateManager::ApplyPassageLandingFloorMC(
             break;
         }
     }
+    if (bCompareLanding)
+    {
+        VoxelGenLOD::RecordSkippedPostComparison(
+            VoxelGenLOD::ETilePostComparisonKind::PassageLandingFloor,
+            !VoxelGenLOD::SameFloatBits(Density, CanonicalDensity));
+    }
 }
 
 static bool VF_IsPassageRoomFloor(
@@ -2844,6 +2957,32 @@ void UVoxelStrateManager::ApplyPassageStructuralPostsMC(
         return;
     }
 
+    const bool bBypass = VoxelGenLOD::IsTilePostReachBypassActive();
+    const bool bLandingReachable = VoxelGenLOD::IsPassageLandingReachable() || bBypass;
+    const bool bStructuralReachable = VoxelGenLOD::IsPassageStructuralReachable() || bBypass;
+    const bool bCompareLanding = VoxelGenLOD::bTilePostReachDebug
+        && !bLandingReachable && !bBypass;
+    float CanonicalDensity = Density;
+    if (bCompareLanding)
+    {
+        const bool PreviousBypass = VoxelGenLOD::bTilePostReachBypass;
+        VoxelGenLOD::bTilePostReachBypass = true;
+        ApplyPassageStructuralPostsMC(
+            CanonicalDensity, WorldX, WorldY, WorldZ,
+            BaseDensity, SealThickness, bProtectAuthoredTunnelFloor);
+        VoxelGenLOD::bTilePostReachBypass = PreviousBypass;
+    }
+    if (!bLandingReachable && !bStructuralReachable)
+    {
+        if (bCompareLanding)
+        {
+            VoxelGenLOD::RecordSkippedPostComparison(
+                VoxelGenLOD::ETilePostComparisonKind::PassageStructuralPosts,
+                !VoxelGenLOD::SameFloatBits(Density, CanonicalDensity));
+        }
+        return;
+    }
+
     VoxelDensityProfile::FScopedTimer ProfileTimer(
         VoxelDensityProfile::EBucket::PassageStructuralPosts);
 
@@ -2873,36 +3012,37 @@ void UVoxelStrateManager::ApplyPassageStructuralPostsMC(
         const FVoxelPassage& Passage = PassageData[PassageIndex];
 
         const bool bTunnelSupportFloor =
-            !bDisableStructuralPosts
+            bStructuralReachable && !bDisableStructuralPosts
             && bPassageSupportFloorWritesEnabled
             && !Passage.bNativeFloorEnabled
             && VF_IsWalkableTunnelFloor(Passage, Position, this, PassageIndex);
-        if (!bSuppressFloor && !bDisableLandingPosts
+        if (!bSuppressFloor && bLandingReachable && !bDisableLandingPosts
             && (VF_IsPassageLandingFloor(Position, Passage.UpperLanding)
                 || VF_IsPassageLandingFloor(Position, Passage.LowerLanding)))
         {
             bAnyLandingFloor = true;
         }
-        if (!bSuppressFloor && !bDisableStructuralPosts && bTunnelSupportFloor)
+        if (!bSuppressFloor && bStructuralReachable
+            && !bDisableStructuralPosts && bTunnelSupportFloor)
         {
             bLegacyTunnelSupportFloor = true;
         }
 
-        if (!bSuppressFloor && !bDisableLandingPosts
+        if (!bSuppressFloor && bLandingReachable && !bDisableLandingPosts
             && (VF_IsPassageRoomFloor(Position, Passage.UpperLanding)
                 || VF_IsPassageRoomFloor(Position, Passage.LowerLanding)))
         {
             bAnyRoomFloor = true;
         }
 
-        if (!bDisableStructuralPosts && !bWalkableAir
+        if (bStructuralReachable && !bDisableStructuralPosts && !bWalkableAir
             && FVector::DistSquared(Position, Passage.BoundCenter) <= Passage.BoundRadiusSq
             && VF_IsWalkableTunnelAir(Passage, Position, this, PassageIndex))
         {
             bWalkableAir = true;
         }
 
-        if (!bDisableLandingPosts
+        if (bLandingReachable && !bDisableLandingPosts
             && FVector::DistSquared(Position, Passage.BoundCenter) <= Passage.BoundRadiusSq)
         {
             const FVoxelPassageLanding* Landings[] = {
@@ -2950,6 +3090,12 @@ void UVoxelStrateManager::ApplyPassageStructuralPostsMC(
         VoxelDensityProfile::AddCounter(
             VoxelDensityProfile::ECounter::PassageSupportFloorBackstopFires);
     }
+    if (bCompareLanding)
+    {
+        VoxelGenLOD::RecordSkippedPostComparison(
+            VoxelGenLOD::ETilePostComparisonKind::PassageStructuralPosts,
+            !VoxelGenLOD::SameFloatBits(Density, CanonicalDensity));
+    }
 }
 
 void UVoxelStrateManager::ApplyPassageNativeFloorMC(
@@ -2960,6 +3106,15 @@ void UVoxelStrateManager::ApplyPassageNativeFloorMC(
     {
         return;
     }
+    if (!VoxelGenLOD::IsPassageStructuralReachable()
+        && !VoxelGenLOD::IsTilePostReachBypassActive())
+    {
+        VoxelGenLOD::CompareSkippedPost(Density, [&]()
+        {
+            ApplyPassageNativeFloorMC(Density, WorldX, WorldY, WorldZ, BaseDensity);
+        }, VoxelGenLOD::ETilePostComparisonKind::PassageNativeFloor);
+        return;
+    }
     const FIntVector ChunkCoord(
         FMath::FloorToInt(WorldX / (float)CHUNK_SIZE),
         FMath::FloorToInt(WorldY / (float)CHUNK_SIZE),
@@ -3018,6 +3173,16 @@ void UVoxelStrateManager::ApplyPassageLandingRoomFloorMC(
     {
         return;
     }
+    if (!VoxelGenLOD::IsPassageLandingReachable()
+        && !VoxelGenLOD::IsTilePostReachBypassActive())
+    {
+        VoxelGenLOD::CompareSkippedPost(Density, [&]()
+        {
+            ApplyPassageLandingRoomFloorMC(
+                Density, WorldX, WorldY, WorldZ, BaseDensity);
+        }, VoxelGenLOD::ETilePostComparisonKind::PassageLandingRoomFloor);
+        return;
+    }
     VoxelDensityProfile::FScopedTimer ProfileTimer(
         VoxelDensityProfile::EBucket::PassageLandingRoomFloor);
     const FIntVector ChunkCoord(
@@ -3912,6 +4077,22 @@ namespace
                    FMath::Min((float)Box.Max.Z, MaxZ),
                    (float)Origin.Z, Step);
     }
+
+    static bool VF_LatticeBoxTouchesSphere(
+        const FBox& Box, const FVector& Center, float Radius)
+    {
+        if (!Box.IsValid || !VoxelMath::IsFinite(Center.X)
+            || !VoxelMath::IsFinite(Center.Y) || !VoxelMath::IsFinite(Center.Z)
+            || !VoxelMath::IsFinite(Radius) || Radius < 0.0f)
+        {
+            return true;
+        }
+        const FVector Closest(
+            FMath::Clamp(Center.X, (float)Box.Min.X, (float)Box.Max.X),
+            FMath::Clamp(Center.Y, (float)Box.Min.Y, (float)Box.Max.Y),
+            FMath::Clamp(Center.Z, (float)Box.Min.Z, (float)Box.Max.Z));
+        return FVector::DistSquared(Closest, Center) <= Radius * Radius;
+    }
 }
 
 bool UVoxelStrateManager::AnyPassageNearLattice(
@@ -4768,6 +4949,189 @@ bool UVoxelStrateManager::AnyPassageLandingFloorNearLattice(
     return false;
 }
 
+bool UVoxelStrateManager::AnyPassageLandingNearLattice(
+    const FBox& VoxelBox, const FIntVector& LatticeOrigin, int32 Step,
+    float ReachScale) const
+{
+    if (Step <= 0 || !VoxelBox.IsValid
+        || !VoxelMath::IsFinite(ReachScale) || ReachScale <= 0.0f)
+    {
+        return true;
+    }
+
+    // VF_ApplyPassageCarving has a hard no-op band at ModSDF >= 4.  A landing term outside the
+    // rounded-room AABB by 4 + K (K=3) is either saturated out of SmoothMin when the tube is
+    // inside the carve band, or leaves the folded result >= 4 when the tube is outside it.  That
+    // proves the landing term cannot change the field; the direct landing/floor posts use their
+    // smaller, operation-specific pads below.
+    for (const FVoxelPassage& Passage : Passages)
+    {
+        if (!VoxelMath::IsFinite(Passage.BoundCenter.X)
+            || !VoxelMath::IsFinite(Passage.BoundCenter.Y)
+            || !VoxelMath::IsFinite(Passage.BoundCenter.Z)
+            || !VoxelMath::IsFinite(Passage.BoundRadius)
+            || !VoxelMath::IsFinite(Passage.BoundRadiusSq)
+            || Passage.BoundRadius < 0.0f || Passage.BoundRadiusSq < 0.0f)
+        {
+            return true;
+        }
+
+        if (Passage.ControlPoints.Num() >= 2)
+        {
+            if (Passage.ControlPoints.Num() > 4096)
+            {
+                return true;
+            }
+            const bool bTaper = Passage.ControlRadii.Num() == Passage.ControlPoints.Num();
+            if (!bTaper && !VoxelMath::IsFinite(Passage.Radius))
+            {
+                return true;
+            }
+            for (int32 PointIndex = 0;
+                 PointIndex < Passage.ControlPoints.Num(); ++PointIndex)
+            {
+                const FVector& Point = Passage.ControlPoints[PointIndex];
+                if (!VoxelMath::IsFinite(Point.X) || !VoxelMath::IsFinite(Point.Y)
+                    || !VoxelMath::IsFinite(Point.Z)
+                    || (bTaper && !VoxelMath::IsFinite(Passage.ControlRadii[PointIndex])))
+                {
+                    return true;
+                }
+            }
+        }
+        else
+        {
+            if (!VoxelMath::IsFinite(Passage.UpperPoint.X)
+                || !VoxelMath::IsFinite(Passage.UpperPoint.Y)
+                || !VoxelMath::IsFinite(Passage.UpperPoint.Z)
+                || !VoxelMath::IsFinite(Passage.LowerPoint.X)
+                || !VoxelMath::IsFinite(Passage.LowerPoint.Y)
+                || !VoxelMath::IsFinite(Passage.LowerPoint.Z)
+                || !VoxelMath::IsFinite(Passage.Radius))
+            {
+                return true;
+            }
+        }
+
+        const FVoxelPassageLanding* Landings[] = {
+            &Passage.UpperLanding, &Passage.LowerLanding };
+        for (const FVoxelPassageLanding* Landing : Landings)
+        {
+            if (!VoxelMath::IsFinite(Landing->StandingPoint.X)
+                || !VoxelMath::IsFinite(Landing->StandingPoint.Y)
+                || !VoxelMath::IsFinite(Landing->FloorZ)
+                || !VoxelMath::IsFinite(Landing->CeilingZ)
+                || !VoxelMath::IsFinite(Landing->HalfWidth)
+                || !VoxelMath::IsFinite(Landing->FloorThickness))
+            {
+                return true;
+            }
+
+            if (Landing->HalfWidth > 0.0f
+                && Landing->FloorThickness > 0.0f
+                && VF_LatticeBoxTouchesAABB(
+                    VoxelBox, LatticeOrigin, Step,
+                    Landing->StandingPoint.X - FMath::Max(Landing->HalfWidth - 1.0f, 0.0f)
+                        - ReachScale,
+                    Landing->StandingPoint.X + FMath::Max(Landing->HalfWidth - 1.0f, 0.0f)
+                        + ReachScale,
+                    Landing->StandingPoint.Y - FMath::Max(Landing->HalfWidth - 1.0f, 0.0f)
+                        - ReachScale,
+                    Landing->StandingPoint.Y + FMath::Max(Landing->HalfWidth - 1.0f, 0.0f)
+                        + ReachScale,
+                    Landing->FloorZ - Landing->FloorThickness - ReachScale,
+                    Landing->FloorZ + ReachScale))
+            {
+                return true;
+            }
+
+            if (Landing->HalfWidth <= 0.0f || Landing->CeilingZ <= Landing->FloorZ)
+            {
+                // VF_EvaluatePassageLandingSDF returns FLT_MAX for this descriptor.  The floor
+                // test above has already handled the only remaining possible writer.
+                continue;
+            }
+
+        }
+    }
+
+    constexpr float SmoothMinK = 3.0f;
+    const float RoomPad = (VoxelPassageGeometry::LandingCarveBlendVoxels + SmoothMinK)
+        * ReachScale;
+    if (!VoxelMath::IsFinite(RoomPad) || RoomPad < 0.0f)
+    {
+        return true;
+    }
+
+    for (const FVoxelPassage& Passage : Passages)
+    {
+        const FVoxelPassageLanding* Landings[] = {
+            &Passage.UpperLanding, &Passage.LowerLanding };
+        for (const FVoxelPassageLanding* Landing : Landings)
+        {
+            if (Landing->HalfWidth <= 0.0f || Landing->CeilingZ <= Landing->FloorZ)
+            {
+                continue;
+            }
+            constexpr float RoomRounding = 1.5f;
+            const float Height = Landing->CeilingZ - Landing->FloorZ;
+            const float HalfX = FMath::Max(Landing->HalfWidth - RoomRounding, 0.25f);
+            const float HalfZ = FMath::Max(Height * 0.5f - RoomRounding, 0.25f);
+            const float CenterZ = (Landing->FloorZ + Landing->CeilingZ) * 0.5f;
+            if (VF_LatticeBoxTouchesAABB(
+                    VoxelBox, LatticeOrigin, Step,
+                    Landing->StandingPoint.X - HalfX - RoomRounding - RoomPad,
+                    Landing->StandingPoint.X + HalfX + RoomRounding + RoomPad,
+                    Landing->StandingPoint.Y - HalfX - RoomRounding - RoomPad,
+                    Landing->StandingPoint.Y + HalfX + RoomRounding + RoomPad,
+                    FMath::Min(Landing->FloorZ,
+                               CenterZ - HalfZ - RoomRounding) - RoomPad,
+                    FMath::Max(Landing->CeilingZ,
+                               CenterZ + HalfZ + RoomRounding) + RoomPad))
+            {
+                return true;
+            }
+        }
+    }
+    return false;
+}
+
+bool UVoxelStrateManager::AnyPassageStructuralPostNearLattice(
+    const FBox& VoxelBox, const FIntVector& LatticeOrigin, int32 Step,
+    float ReachScale) const
+{
+    (void)LatticeOrigin;
+    (void)Step;
+    if (Step <= 0 || !VoxelBox.IsValid
+        || !VoxelMath::IsFinite(ReachScale) || ReachScale <= 0.0f)
+    {
+        return true;
+    }
+
+    // The construction-time BoundRadius encloses every tube, landing room, floor band, and its
+    // four-voxel carve margin.  All structural writers below are subsets of that sphere, so a
+    // sphere/AABB miss proves identity without doing a per-sample chunk-shortlist lookup.
+    for (const FVoxelPassage& Passage : Passages)
+    {
+        if (!VoxelMath::IsFinite(Passage.BoundCenter.X)
+            || !VoxelMath::IsFinite(Passage.BoundCenter.Y)
+            || !VoxelMath::IsFinite(Passage.BoundCenter.Z)
+            || !VoxelMath::IsFinite(Passage.BoundRadius)
+            || !VoxelMath::IsFinite(Passage.BoundRadiusSq)
+            || Passage.BoundRadius < 0.0f || Passage.BoundRadiusSq < 0.0f)
+        {
+            return true;
+        }
+        const float Reach = (Passage.BoundRadius + 1.0f) * ReachScale;
+        if (!VoxelMath::IsFinite(Reach)
+            || VF_LatticeBoxTouchesSphere(VoxelBox, Passage.BoundCenter, Reach))
+        {
+            return true;
+        }
+    }
+    return false;
+}
+
 bool UVoxelStrateManager::AnyLandingFloorAtLattice(
     const FBox& VoxelBox, const FIntVector& LatticeOrigin, int32 Step) const
 {
@@ -5013,9 +5377,14 @@ bool UVoxelStrateManager::AnyOriginLandingFloorNearBox(
 }
 
 bool UVoxelStrateManager::AnyOriginLandingNearLattice(
-    const FBox& VoxelBox, const FIntVector& LatticeOrigin, int32 Step) const
+    const FBox& VoxelBox, const FIntVector& LatticeOrigin, int32 Step,
+    float ReachScale) const
 {
     if (OriginSpineRadius <= 0.0f) return false;
+    if (!VoxelMath::IsFinite(ReachScale) || ReachScale <= 0.0f)
+    {
+        return true;
+    }
     for (const FStrateSlot& Slot : StrateLayout)
     {
         if (Slot.Definition == nullptr) continue;
@@ -5023,7 +5392,8 @@ bool UVoxelStrateManager::AnyOriginLandingNearLattice(
         const float BottomZ = static_cast<float>(Slot.BottomChunkZ) * CHUNK_SIZE;
         const float Seal = VF_BoundarySealThicknessForDefinition(*Slot.Definition);
         if (VoxelPassageGeometry::OriginLandingRoomTouchesLattice(
-                VoxelBox, LatticeOrigin, Step, TopZ, BottomZ, Seal, OriginSpineRadius))
+                VoxelBox, LatticeOrigin, Step, TopZ, BottomZ, Seal, OriginSpineRadius,
+                ReachScale))
         {
             return true;
         }

Source/VoxelForge/Private/VoxelWorld.cpp

@@ -19,6 +19,7 @@
 #include "VoxelStats.h"
 #include "VoxelCaveMorphology.h"
 #include "VoxelPassageGeometry.h"
+#include "VoxelTilePostReach.h"
 // IWYU (FPSemantics = Precise ⇒ plus de PCH partagé) : GetPlayerPosition déréférence le pawn, donc
 // APawn doit être COMPLET — `Casts.h` n'en donne qu'une déclaration avant. APlayerController était
 // complet par transitivité seulement : on l'inclut explicitement, c'est exactement la fragilité
@@ -1132,6 +1133,98 @@ void AVoxelWorld::EndPlay(const EEndPlayReason::Type EndPlayReason)
     }
     VoxelCaveMorphology::LogPlayerFitMemoStats();
     LogStreamingLatencySummary();
+    const uint64 TilePostReachDifferences =
+        VoxelGenLOD::GSkippedPostDifferences.load(std::memory_order_relaxed);
+    UE_LOG(LogTemp, Display,
+        TEXT("[VoxelForgeTilePostReach] tiles=%llu origin_reachable=%llu origin_skipped=%llu "
+             "passage_landing_reachable=%llu passage_landing_skipped=%llu "
+             "passage_structural_reachable=%llu passage_structural_skipped=%llu "
+             "debug=%d comparisons=%llu differences=%llu"),
+        static_cast<unsigned long long>(
+            VoxelGenLOD::GTilePostReachTileCount.load(std::memory_order_relaxed)),
+        static_cast<unsigned long long>(
+            VoxelGenLOD::GOriginLandingReachableTiles.load(std::memory_order_relaxed)),
+        static_cast<unsigned long long>(
+            VoxelGenLOD::GOriginLandingSkippedTiles.load(std::memory_order_relaxed)),
+        static_cast<unsigned long long>(
+            VoxelGenLOD::GPassageLandingReachableTiles.load(std::memory_order_relaxed)),
+        static_cast<unsigned long long>(
+            VoxelGenLOD::GPassageLandingSkippedTiles.load(std::memory_order_relaxed)),
+        static_cast<unsigned long long>(
+            VoxelGenLOD::GPassageStructuralReachableTiles.load(std::memory_order_relaxed)),
+        static_cast<unsigned long long>(
+            VoxelGenLOD::GPassageStructuralSkippedTiles.load(std::memory_order_relaxed)),
+        VoxelGenLOD::GTilePostReachDebugEnabled.load(std::memory_order_relaxed) ? 1 : 0,
+        static_cast<unsigned long long>(
+            VoxelGenLOD::GSkippedPostComparisons.load(std::memory_order_relaxed)),
+        static_cast<unsigned long long>(TilePostReachDifferences));
+    UE_LOG(LogTemp, Display,
+        TEXT("[VoxelForgeTilePostReachKinds] comparisons="
+             "origin_air=%llu/origin_floor=%llu/passage_sdf=%llu/landing_air=%llu/"
+             "tunnel_air=%llu/landing_floor=%llu/structural=%llu/native_floor=%llu/room_floor=%llu "
+             "differences=%llu/%llu/%llu/%llu/%llu/%llu/%llu/%llu/%llu"),
+        static_cast<unsigned long long>(VoxelGenLOD::GSkippedPostComparisonsByKind[
+            static_cast<uint8>(VoxelGenLOD::ETilePostComparisonKind::OriginAir)].load(
+                std::memory_order_relaxed)),
+        static_cast<unsigned long long>(VoxelGenLOD::GSkippedPostComparisonsByKind[
+            static_cast<uint8>(VoxelGenLOD::ETilePostComparisonKind::OriginFloor)].load(
+                std::memory_order_relaxed)),
+        static_cast<unsigned long long>(VoxelGenLOD::GSkippedPostComparisonsByKind[
+            static_cast<uint8>(VoxelGenLOD::ETilePostComparisonKind::PassageLandingSDF)].load(
+                std::memory_order_relaxed)),
+        static_cast<unsigned long long>(VoxelGenLOD::GSkippedPostComparisonsByKind[
+            static_cast<uint8>(VoxelGenLOD::ETilePostComparisonKind::PassageLandingAir)].load(
+                std::memory_order_relaxed)),
+        static_cast<unsigned long long>(VoxelGenLOD::GSkippedPostComparisonsByKind[
+            static_cast<uint8>(VoxelGenLOD::ETilePostComparisonKind::PassageTunnelAir)].load(
+                std::memory_order_relaxed)),
+        static_cast<unsigned long long>(VoxelGenLOD::GSkippedPostComparisonsByKind[
+            static_cast<uint8>(VoxelGenLOD::ETilePostComparisonKind::PassageLandingFloor)].load(
+                std::memory_order_relaxed)),
+        static_cast<unsigned long long>(VoxelGenLOD::GSkippedPostComparisonsByKind[
+            static_cast<uint8>(VoxelGenLOD::ETilePostComparisonKind::PassageStructuralPosts)].load(
+                std::memory_order_relaxed)),
+        static_cast<unsigned long long>(VoxelGenLOD::GSkippedPostComparisonsByKind[
+            static_cast<uint8>(VoxelGenLOD::ETilePostComparisonKind::PassageNativeFloor)].load(
+                std::memory_order_relaxed)),
+        static_cast<unsigned long long>(VoxelGenLOD::GSkippedPostComparisonsByKind[
+            static_cast<uint8>(VoxelGenLOD::ETilePostComparisonKind::PassageLandingRoomFloor)].load(
+                std::memory_order_relaxed)),
+        static_cast<unsigned long long>(VoxelGenLOD::GSkippedPostDifferencesByKind[
+            static_cast<uint8>(VoxelGenLOD::ETilePostComparisonKind::OriginAir)].load(
+                std::memory_order_relaxed)),
+        static_cast<unsigned long long>(VoxelGenLOD::GSkippedPostDifferencesByKind[
+            static_cast<uint8>(VoxelGenLOD::ETilePostComparisonKind::OriginFloor)].load(
+                std::memory_order_relaxed)),
+        static_cast<unsigned long long>(VoxelGenLOD::GSkippedPostDifferencesByKind[
+            static_cast<uint8>(VoxelGenLOD::ETilePostComparisonKind::PassageLandingSDF)].load(
+                std::memory_order_relaxed)),
+        static_cast<unsigned long long>(VoxelGenLOD::GSkippedPostDifferencesByKind[
+            static_cast<uint8>(VoxelGenLOD::ETilePostComparisonKind::PassageLandingAir)].load(
+                std::memory_order_relaxed)),
+        static_cast<unsigned long long>(VoxelGenLOD::GSkippedPostDifferencesByKind[
+            static_cast<uint8>(VoxelGenLOD::ETilePostComparisonKind::PassageTunnelAir)].load(
+                std::memory_order_relaxed)),
+        static_cast<unsigned long long>(VoxelGenLOD::GSkippedPostDifferencesByKind[
+            static_cast<uint8>(VoxelGenLOD::ETilePostComparisonKind::PassageLandingFloor)].load(
+                std::memory_order_relaxed)),
+        static_cast<unsigned long long>(VoxelGenLOD::GSkippedPostDifferencesByKind[
+            static_cast<uint8>(VoxelGenLOD::ETilePostComparisonKind::PassageStructuralPosts)].load(
+                std::memory_order_relaxed)),
+        static_cast<unsigned long long>(VoxelGenLOD::GSkippedPostDifferencesByKind[
+            static_cast<uint8>(VoxelGenLOD::ETilePostComparisonKind::PassageNativeFloor)].load(
+                std::memory_order_relaxed)),
+        static_cast<unsigned long long>(VoxelGenLOD::GSkippedPostDifferencesByKind[
+            static_cast<uint8>(VoxelGenLOD::ETilePostComparisonKind::PassageLandingRoomFloor)].load(
+                std::memory_order_relaxed)));
+    if (VoxelGenLOD::GTilePostReachDebugEnabled.load(std::memory_order_relaxed)
+        && TilePostReachDifferences != 0)
+    {
+        UE_LOG(LogTemp, Error,
+            TEXT("[VoxelForgeTilePostReach] soundness failure: skipped post changed the field."));
+        FPlatformMisc::RequestExitWithStatus(
+            false, 1, TEXT("VoxelForge tile post reach soundness failure"));
+    }
     PendingTiles.Empty();
     PendingTileCancellation.Empty();
     PendingUnload.Empty();

Source/VoxelForge/Public/VoxelDensityPrimitives.h

@@ -28,6 +28,7 @@
 #include "VoxelTypes.h"   // SmoothStep01
 #include "VoxelPassageGeometry.h" // shared body-sized landing/tunnel geometry
 #include "VoxelDensityAblation.h" // development-only world-changing measurements
+#include "VoxelTilePostReach.h" // worker-local landing/structural post reach bits
 
 //=============================================================================
 // SEAL DE FRONTIÈRE / BOUNDARY SEAL
@@ -193,6 +194,17 @@ FORCEINLINE void VF_ApplyOriginLandingAirMC(float& Density,
     float WorldX, float WorldY, float WorldZ,
     float StrateTopZ, float StrateBottomZ, float SealThickness, float BaseDensity, float Radius)
 {
+    if (!VoxelGenLOD::IsOriginLandingReachable()
+        && !VoxelGenLOD::IsTilePostReachBypassActive())
+    {
+        VoxelGenLOD::CompareSkippedPost(Density, [&]()
+        {
+            VF_ApplyOriginLandingAirMC(
+                Density, WorldX, WorldY, WorldZ,
+                StrateTopZ, StrateBottomZ, SealThickness, BaseDensity, Radius);
+        }, VoxelGenLOD::ETilePostComparisonKind::OriginAir);
+        return;
+    }
     float InternalDensity = -Density;
     VF_ApplyOriginLandingAir(InternalDensity, WorldX, WorldY, WorldZ,
         StrateTopZ, StrateBottomZ, SealThickness, BaseDensity, Radius);
@@ -204,6 +216,17 @@ FORCEINLINE void VF_ApplyOriginLandingFloorMC(float& Density,
     float WorldX, float WorldY, float WorldZ,
     float StrateTopZ, float StrateBottomZ, float SealThickness, float BaseDensity, float Radius)
 {
+    if (!VoxelGenLOD::IsOriginLandingReachable()
+        && !VoxelGenLOD::IsTilePostReachBypassActive())
+    {
+        VoxelGenLOD::CompareSkippedPost(Density, [&]()
+        {
+            VF_ApplyOriginLandingFloorMC(
+                Density, WorldX, WorldY, WorldZ,
+                StrateTopZ, StrateBottomZ, SealThickness, BaseDensity, Radius);
+        }, VoxelGenLOD::ETilePostComparisonKind::OriginFloor);
+        return;
+    }
     float InternalDensity = -Density;
     VF_ApplyOriginLandingFloor(InternalDensity, WorldX, WorldY, WorldZ,
         StrateTopZ, StrateBottomZ, SealThickness, BaseDensity, Radius);

Source/VoxelForge/Public/VoxelPassageGeometry.h

@@ -471,13 +471,20 @@ namespace VoxelPassageGeometry
 
     FORCEINLINE bool OriginLandingRoomTouchesLattice(
         const FBox& VoxelBox, const FIntVector& LatticeOrigin, int32 Step,
-        float StrateTopZ, float StrateBottomZ, float SealThickness, float OriginRadius)
+        float StrateTopZ, float StrateBottomZ, float SealThickness, float OriginRadius,
+        float ReachScale = 1.0f)
     {
         if (!VoxelBox.IsValid) return false;
+        if (!VoxelMath::IsFinite(ReachScale) || ReachScale <= 0.0f)
+        {
+            // This is an invalid proof request, not an empty room.  The manager treats a
+            // malformed scale as conservative/unknown before calling this helper.
+            return true;
+        }
         const FOriginLandingGeometry Geometry = BuildOriginLandingGeometry(
             StrateTopZ, StrateBottomZ, SealThickness, OriginRadius);
         if (!Geometry.bValid) return false;
-        const float Pad = LandingCarveBlendVoxels;
+        const float Pad = LandingCarveBlendVoxels * ReachScale;
         return LatticeAxisHasSampleInInterval(
                    FMath::Max((float)VoxelBox.Min.X, -Geometry.HalfWidth - Pad),
                    FMath::Min((float)VoxelBox.Max.X, Geometry.HalfWidth + Pad),

Source/VoxelForge/Public/VoxelStrateManager.h

@@ -472,6 +472,14 @@ public:
                                       float BaseDensity, float SealThickness) const;
     bool AnyPassageLandingFloorNearLattice(const FBox& VoxelBox,
                                            const FIntVector& LatticeOrigin, int32 Step) const;
+    /** Conservative landing-room plus floor reach for the exact MC lattice and its halo. */
+    bool AnyPassageLandingNearLattice(const FBox& VoxelBox,
+                                      const FIntVector& LatticeOrigin, int32 Step,
+                                      float ReachScale = 1.0f) const;
+    /** Conservative sphere guard for all passage-owned structural posts and native D-floors. */
+    bool AnyPassageStructuralPostNearLattice(const FBox& VoxelBox,
+                                             const FIntVector& LatticeOrigin, int32 Step,
+                                             float ReachScale = 1.0f) const;
     /** Exact presence test for a structural floor write on the MC lattice. */
     bool AnyLandingFloorAtLattice(const FBox& VoxelBox,
                                   const FIntVector& LatticeOrigin, int32 Step) const;
@@ -481,7 +489,8 @@ public:
     bool AnyOriginLandingFloorNearBox(const FVector& MinVoxel, const FVector& MaxVoxel) const;
 
     bool AnyOriginLandingNearLattice(const FBox& VoxelBox,
-                                     const FIntVector& LatticeOrigin, int32 Step) const;
+                                     const FIntVector& LatticeOrigin, int32 Step,
+                                     float ReachScale = 1.0f) const;
     /** Exact conservative candidate for the post-disturbance origin-room air reassertion. */
     bool AnyOriginLandingAirNearLattice(const FBox& VoxelBox,
                                         const FIntVector& LatticeOrigin, int32 Step,

Source/VoxelForge/Public/VoxelTilePostReach.h

@@ -0,0 +1,183 @@
+// Per-tile reach state for density posts.
+//
+// The marching-cubes worker installs this state once for the tile's lattice plus its one-point
+// halo.  Density helpers only read the bit that owns them.  The inline TLS is intentional: the
+// runtime hot path must not cross a DLL boundary for a single boolean load.
+
+#pragma once
+
+#include "CoreMinimal.h"
+
+#include <atomic>
+
+namespace VoxelGenLOD
+{
+    enum ETilePostReach : uint8
+    {
+        OriginLandingReachable    = 1u << 0,
+        PassageLandingReachable   = 1u << 1,
+        PassageStructuralReachable= 1u << 2,
+        AllTilePostReach          = OriginLandingReachable
+                                  | PassageLandingReachable
+                                  | PassageStructuralReachable,
+    };
+
+    enum class ETilePostComparisonKind : uint8
+    {
+        Other = 0,
+        OriginAir,
+        OriginFloor,
+        PassageLandingSDF,
+        PassageLandingAir,
+        PassageTunnelAir,
+        PassageLandingFloor,
+        PassageStructuralPosts,
+        PassageNativeFloor,
+        PassageLandingRoomFloor,
+        Count,
+    };
+
+    // A tile that is not being meshed, or a point query outside the mesher, must retain the
+    // canonical behaviour.  GenerateMesh scopes this to its computed mask.
+    inline thread_local uint8 TilePostReachFlags = AllTilePostReach;
+    inline thread_local bool bTilePostReachDebug = false;
+    inline thread_local bool bTilePostReachBypass = false;
+
+    // These are diagnostics only.  They never participate in a field decision.
+    inline std::atomic<bool> GTilePostReachDebugEnabled { false };
+    inline std::atomic<uint64> GTilePostReachTileCount { 0 };
+    inline std::atomic<uint64> GOriginLandingReachableTiles { 0 };
+    inline std::atomic<uint64> GPassageLandingReachableTiles { 0 };
+    inline std::atomic<uint64> GPassageStructuralReachableTiles { 0 };
+    inline std::atomic<uint64> GOriginLandingSkippedTiles { 0 };
+    inline std::atomic<uint64> GPassageLandingSkippedTiles { 0 };
+    inline std::atomic<uint64> GPassageStructuralSkippedTiles { 0 };
+    inline std::atomic<uint64> GSkippedPostComparisons { 0 };
+    inline std::atomic<uint64> GSkippedPostDifferences { 0 };
+    inline std::atomic<uint64> GSkippedPostComparisonsByKind[
+        static_cast<uint8>(ETilePostComparisonKind::Count)]{};
+    inline std::atomic<uint64> GSkippedPostDifferencesByKind[
+        static_cast<uint8>(ETilePostComparisonKind::Count)]{};
+
+    FORCEINLINE bool IsTilePostReachable(uint8 Bit)
+    {
+        return (TilePostReachFlags & Bit) != 0;
+    }
+
+    FORCEINLINE bool IsOriginLandingReachable()
+    {
+        return IsTilePostReachable(OriginLandingReachable);
+    }
+
+    FORCEINLINE bool IsPassageLandingReachable()
+    {
+        return IsTilePostReachable(PassageLandingReachable);
+    }
+
+    FORCEINLINE bool IsPassageStructuralReachable()
+    {
+        return IsTilePostReachable(PassageStructuralReachable);
+    }
+
+    FORCEINLINE bool IsTilePostReachBypassActive()
+    {
+        return bTilePostReachBypass;
+    }
+
+    FORCEINLINE void RecordTileReachMask(uint8 Flags)
+    {
+        GTilePostReachTileCount.fetch_add(1, std::memory_order_relaxed);
+        if ((Flags & OriginLandingReachable) != 0)
+        {
+            GOriginLandingReachableTiles.fetch_add(1, std::memory_order_relaxed);
+        }
+        else
+        {
+            GOriginLandingSkippedTiles.fetch_add(1, std::memory_order_relaxed);
+        }
+        if ((Flags & PassageLandingReachable) != 0)
+        {
+            GPassageLandingReachableTiles.fetch_add(1, std::memory_order_relaxed);
+        }
+        else
+        {
+            GPassageLandingSkippedTiles.fetch_add(1, std::memory_order_relaxed);
+        }
+        if ((Flags & PassageStructuralReachable) != 0)
+        {
+            GPassageStructuralReachableTiles.fetch_add(1, std::memory_order_relaxed);
+        }
+        else
+        {
+            GPassageStructuralSkippedTiles.fetch_add(1, std::memory_order_relaxed);
+        }
+    }
+
+    FORCEINLINE bool SameFloatBits(float A, float B)
+    {
+        uint32 ABits = 0;
+        uint32 BBits = 0;
+        FMemory::Memcpy(&ABits, &A, sizeof(float));
+        FMemory::Memcpy(&BBits, &B, sizeof(float));
+        return ABits == BBits;
+    }
+
+    FORCEINLINE void RecordSkippedPostComparison(
+        ETilePostComparisonKind Kind, bool bDifferent)
+    {
+        GSkippedPostComparisons.fetch_add(1, std::memory_order_relaxed);
+        const uint8 KindIndex = static_cast<uint8>(Kind);
+        if (KindIndex < static_cast<uint8>(ETilePostComparisonKind::Count))
+        {
+            GSkippedPostComparisonsByKind[KindIndex].fetch_add(
+                1, std::memory_order_relaxed);
+        }
+        if (bDifferent)
+        {
+            GSkippedPostDifferences.fetch_add(1, std::memory_order_relaxed);
+            if (KindIndex < static_cast<uint8>(ETilePostComparisonKind::Count))
+            {
+                GSkippedPostDifferencesByKind[KindIndex].fetch_add(
+                    1, std::memory_order_relaxed);
+            }
+        }
+    }
+
+    FORCEINLINE void RecordSkippedPostComparison(bool bDifferent)
+    {
+        RecordSkippedPostComparison(ETilePostComparisonKind::Other, bDifferent);
+    }
+
+    /** Run one skipped float post through its canonical body, then restore the fast-path value. */
+    template <typename CallableType>
+    FORCEINLINE void CompareSkippedPost(
+        float& Density, CallableType Callable,
+        ETilePostComparisonKind Kind = ETilePostComparisonKind::Other)
+    {
+        if (!bTilePostReachDebug || bTilePostReachBypass)
+        {
+            return;
+        }
+
+        const float Before = Density;
+        {
+            const bool PreviousBypass = bTilePostReachBypass;
+            bTilePostReachBypass = true;
+            Callable();
+            bTilePostReachBypass = PreviousBypass;
+        }
+        RecordSkippedPostComparison(Kind, !SameFloatBits(Before, Density));
+        Density = Before;
+    }
+
+    /** Compare a scalar proof input such as EvaluateModifierSDF without changing the field. */
+    FORCEINLINE void CompareSkippedPostValue(
+        float Candidate, float Canonical,
+        ETilePostComparisonKind Kind = ETilePostComparisonKind::Other)
+    {
+        if (bTilePostReachDebug && !bTilePostReachBypass)
+        {
+            RecordSkippedPostComparison(Kind, !SameFloatBits(Candidate, Canonical));
+        }
+    }
+}