wip(assembler): M1 round 6 -- owner walk fixes: 25 cm geometry scale, one height datum, carve/fill sign, faster relief meshing

Owner saw content floating above native terrain, spiky triangles, reversed carve/fill and late relief.
Causes: shared mesher placed Core tiles on a 12.5 cm grid; content/atmosphere asked strate ranges in
12.5 cm voxels; Core edits add density where the legacy diff subtracts. Horizon LOD8 bridge edge
5.657 -> 2.265 cells. Relief mesh p95 60.8 -> 42.0 ms (LOD0). New BuildHost checks for scale, height,
blueprint carve/fill and per-kind streaming lag.

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

Source/VoxelForge/Private/VoxelWorld.cpp

@@ -2403,6 +2403,7 @@ void AVoxelWorld::BeginPlay()
 
     Generator->InitializeSettings(Settings);
     Mesher->SetGenerator(Generator);
+    Mesher->SetGeometryVoxelSizeCm(GetActiveVoxelSizeCm());
     Mesher->SetShutdownFlag(&bShuttingDown);
     Mesher->bGenerateSkirts = Settings->bGenerateSkirts;
     Mesher->SkirtCells      = Settings->SkirtCells;
@@ -12476,10 +12477,21 @@ int32 AVoxelWorld::GetStrateAtPosition(FVector WorldPosition) const
     // GetStrateIndex veut des cm ACTEUR-LOCAUX (il convertit cm -> voxels lui-meme).
     // GetStrateIndex wants actor-LOCAL cm (it does the cm -> voxel conversion itself).
     const float LocalZCm = WorldToLocalCm(WorldPosition).Z;
-    const float StrateManagerZCm = bUseVoxelForgeCore
+    return StrateManager->GetStrateIndex(ToStrateManagerLocalZ(LocalZCm));
+}
+
+float AVoxelWorld::ToStrateManagerLocalZ(float LocalZCm) const
+{
+    return bUseVoxelForgeCore
         ? (LocalZCm / GetActiveVoxelSizeCm()) * VOXEL_SIZE
         : LocalZCm;
-    return StrateManager->GetStrateIndex(StrateManagerZCm);
+}
+
+float AVoxelWorld::FromStrateManagerLocalZ(float ManagerLocalZCm) const
+{
+    return bUseVoxelForgeCore
+        ? (ManagerLocalZCm / VOXEL_SIZE) * GetActiveVoxelSizeCm()
+        : ManagerLocalZCm;
 }
 
 FVoxelBiomeQuery AVoxelWorld::GetBiomeAtWorldLocation(FVector WorldLocation) const
@@ -12610,8 +12622,9 @@ void AVoxelWorld::CarveAtPosition(FVector Position, float Radius, float Strength
 {
     FVoxelModification Mod;
     Mod.Center = WorldToLocalVoxel(Position);    // world cm → voxel space
-    Mod.Radius = Radius * GetLegacyVoxelToActiveVoxelScale();
-    Mod.Strength = -FMath::Abs(Strength);  // force negative for carving
+    const float VoxelScale = GetLegacyVoxelToActiveVoxelScale();
+    Mod.Radius = Radius * VoxelScale;
+    Mod.Strength = -FMath::Abs(Strength) * VoxelScale;  // force negative for carving / Force le signe negatif pour creuser.
     ApplyModification(Mod);
 }
 
@@ -12619,8 +12632,9 @@ void AVoxelWorld::FillAtPosition(FVector Position, float Radius, float Strength)
 {
     FVoxelModification Mod;
     Mod.Center = WorldToLocalVoxel(Position);
-    Mod.Radius = Radius * GetLegacyVoxelToActiveVoxelScale();
-    Mod.Strength = FMath::Abs(Strength);   // force positive for filling
+    const float VoxelScale = GetLegacyVoxelToActiveVoxelScale();
+    Mod.Radius = Radius * VoxelScale;
+    Mod.Strength = FMath::Abs(Strength) * VoxelScale;   // force positive for filling / Force le signe positif pour remplir.
     ApplyModification(Mod);
 }
 
@@ -12811,7 +12825,9 @@ void AVoxelWorld::ApplyCoreModification(const FVoxelModification& Modification)
     Brush.halfExtent = {Modification.BoxExtent.X, Modification.BoxExtent.Y, Modification.BoxExtent.Z};
     Brush.radius = FMath::Max(0.0f, Modification.Radius);
     Brush.falloff = FMath::Max(0.0f, Modification.Falloff);
-    Brush.strength = Modification.Strength;
+    // Legacy subtracts the modification offset; Core's densityOffset operation adds it.
+    // Le legacy soustrait le decalage; l'operation densityOffset de Core l'ajoute.
+    Brush.strength = -Modification.Strength;
     switch (Modification.Shape)
     {
     case EVoxelBrushShape::Box:
@@ -12971,7 +12987,7 @@ void AVoxelWorld::CarveBox(FVector Position, FVector ExtentVoxels, float Strengt
     Mod.BoxExtent = ExtentVoxels * VoxelScale;
     Mod.Falloff *= VoxelScale;
     Mod.Radius = ExtentVoxels.GetMax() * VoxelScale; // budget proxy
-    Mod.Strength = -FMath::Abs(Strength);       // carve
+    Mod.Strength = -FMath::Abs(Strength) * VoxelScale;       // carve / creuser
     ApplyModification(Mod);
 }
 
@@ -12984,7 +13000,7 @@ void AVoxelWorld::FillBox(FVector Position, FVector ExtentVoxels, float Strength
     Mod.BoxExtent = ExtentVoxels * VoxelScale;
     Mod.Falloff *= VoxelScale;
     Mod.Radius = ExtentVoxels.GetMax() * VoxelScale;
-    Mod.Strength = FMath::Abs(Strength);        // fill
+    Mod.Strength = FMath::Abs(Strength) * VoxelScale;        // fill / remplir
     ApplyModification(Mod);
 }
 
@@ -12997,7 +13013,7 @@ void AVoxelWorld::CarveCapsule(FVector WorldA, FVector WorldB, float RadiusVoxel
     const float VoxelScale = GetLegacyVoxelToActiveVoxelScale();
     Mod.Radius = RadiusVoxels * VoxelScale;
     Mod.Falloff *= VoxelScale;
-    Mod.Strength = -FMath::Abs(Strength);
+    Mod.Strength = -FMath::Abs(Strength) * VoxelScale;
     ApplyModification(Mod);
 }
 
@@ -13010,7 +13026,7 @@ void AVoxelWorld::FillCapsule(FVector WorldA, FVector WorldB, float RadiusVoxels
     const float VoxelScale = GetLegacyVoxelToActiveVoxelScale();
     Mod.Radius = RadiusVoxels * VoxelScale;
     Mod.Falloff *= VoxelScale;
-    Mod.Strength = FMath::Abs(Strength);
+    Mod.Strength = FMath::Abs(Strength) * VoxelScale;
     ApplyModification(Mod);
 }