proto: continuous swept road deck; coarse-LOD proxies keep thin pillars intact (L143)

Road: one swept-deck stamp on a shared cubic-Hermite centerline (stamp vocabulary V5), 376.8 m, max 8.5 deg, walk
audit clean, short-road control fails as expected. Pillars: regular fillPillar stamps get deterministic 24-sided
capped-cylinder proxies once the LOD step exceeds their radius or half-height (applies to all worlds). Owner hashes
unchanged (v227); five-fixture Clang/GCC determinism; fast tier green.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016dhxM43dnWvUu2B5Ph1iG1

Standalone/Core/src/ShapeWorldInternal.h

@@ -3536,6 +3536,7 @@ private:
         const VoxelForgeCore::ResolvedLayoutStampV1* record=nullptr;
         std::array<float,3> positionVoxels{},halfExtentsVoxels{};
         std::array<std::array<float,3>,2> sweepEndpointsVoxels{};
+        std::vector<std::array<float,3>> sweepPathVoxels;
         float smoothWidthVoxels=0.0f;
         float irregularityAmplitudeVoxels=0.0f;
         float irregularityWavelengthVoxels=0.0f;
@@ -3710,6 +3711,15 @@ private:
                         static_cast<double>(stamp.sweepEndpointsMicrometres[endpoint][axis])
                             /Owner->CoreVoxelSizeMicrons);
             }
+            runtime.sweepPathVoxels.reserve(stamp.sweepPathMicrometres.size());
+            for(const auto& pointMicrometres:stamp.sweepPathMicrometres)
+            {
+                std::array<float,3> point{};
+                for(std::size_t axis=0;axis<3;++axis)
+                    point[axis]=static_cast<float>(static_cast<double>(pointMicrometres[axis])
+                        /Owner->CoreVoxelSizeMicrons);
+                runtime.sweepPathVoxels.push_back(point);
+            }
             const std::size_t xAxis=stamp.yawQuarterTurns%2?1:0;
             const std::size_t yAxis=stamp.yawQuarterTurns%2?0:1;
             runtime.halfExtentsVoxels={
@@ -5169,6 +5179,20 @@ private:
     }
 
 public:
+    static std::int32_t& CurrentStampSamplingStep() noexcept
+    {
+        static thread_local std::int32_t Step=0;
+        return Step;
+    }
+    struct FScopedStampSamplingStep
+    {
+        explicit FScopedStampSamplingStep(std::int32_t Step)
+            :Previous(CurrentStampSamplingStep())
+        {CurrentStampSamplingStep()=std::max(0,Step);}
+        ~FScopedStampSamplingStep(){CurrentStampSamplingStep()=Previous;}
+        std::int32_t Previous=0;
+    };
+
     bool GetNativeSurfaceHeightsAt(float X,float Y,int32 ChunkZ,
                                    float& OutGroundZ,float& OutCeilingZ) const
     {
@@ -7123,6 +7147,111 @@ private:
         const float top=std::max(StampEllipsoidSdf(x,y,z,halfSize),-z);
         return SmoothMinDistance(lower,top,round*2.0f);
     }
+    static float StampContinuousSweptDeckSdf(const FStampRuntime& stamp,
+        float x,float y,float z)
+    {
+        const auto& path=stamp.sweepPathVoxels;
+        if(path.size()<2)return std::numeric_limits<float>::infinity();
+        const float halfWidth=stamp.halfExtentsVoxels[1];
+        const float halfThickness=stamp.halfExtentsVoxels[2];
+        const float round=std::min(0.35f,std::min(halfWidth,halfThickness)*0.15f);
+        const float searchMargin=halfWidth+halfThickness+2.0f;
+        const auto first=std::lower_bound(path.begin(),path.end(),x-searchMargin,
+            [](const auto& point,float value){return point[0]<value;});
+        const auto last=std::upper_bound(first,path.end(),x+searchMargin,
+            [](float value,const auto& point){return value<point[0];});
+        const std::size_t firstIndex=static_cast<std::size_t>(first-path.begin());
+        const std::size_t lastIndex=static_cast<std::size_t>(last-path.begin());
+        const std::size_t segmentBegin=std::min(path.size()-2,
+            firstIndex==0?std::size_t{0}:firstIndex-1);
+        const std::size_t segmentEnd=std::min(path.size()-2,lastIndex);
+        std::size_t nearestSegment=path.size();
+        float nearestProjection=0.0f;
+        float nearestDistanceSquared=std::numeric_limits<float>::infinity();
+        for(std::size_t segment=segmentBegin;segment<=segmentEnd;++segment)
+        {
+            const auto& a=path[segment];const auto& b=path[segment+1];
+            const float dx=b[0]-a[0],dy=b[1]-a[1];
+            const float horizontalSquared=dx*dx+dy*dy;
+            if(!(horizontalSquared>1.0e-10f))continue;
+            const float projection=std::clamp(((x-a[0])*dx+(y-a[1])*dy)
+                /horizontalSquared,0.0f,1.0f);
+            const float nearestX=a[0]+projection*dx;
+            const float nearestY=a[1]+projection*dy;
+            const float offsetX=x-nearestX,offsetY=y-nearestY;
+            const float distanceSquared=offsetX*offsetX+offsetY*offsetY;
+            if(distanceSquared<nearestDistanceSquared
+                ||(distanceSquared==nearestDistanceSquared&&segment<nearestSegment))
+            {
+                nearestSegment=segment;
+                nearestProjection=projection;
+                nearestDistanceSquared=distanceSquared;
+            }
+        }
+        if(nearestSegment>=path.size()-1)return std::numeric_limits<float>::infinity();
+        const auto evalCenterline=[&](float parameter,std::array<float,3>& center,
+            std::array<float,3>& tangent)
+        {
+            const auto& p0=path[nearestSegment];
+            const auto& p1=path[nearestSegment+1];
+            const auto& before=path[nearestSegment==0?nearestSegment:nearestSegment-1];
+            const auto& after=path[nearestSegment+2<path.size()
+                ?nearestSegment+2:nearestSegment+1];
+            const float t2=parameter*parameter,t3=t2*parameter;
+            const float h00=2.0f*t3-3.0f*t2+1.0f;
+            const float h10=t3-2.0f*t2+parameter;
+            const float h01=-2.0f*t3+3.0f*t2;
+            const float h11=t3-t2;
+            const float d00=6.0f*t2-6.0f*parameter;
+            const float d10=3.0f*t2-4.0f*parameter+1.0f;
+            const float d01=-6.0f*t2+6.0f*parameter;
+            const float d11=3.0f*t2-2.0f*parameter;
+            for(std::size_t axis=0;axis<3;++axis)
+            {
+                const float m0=nearestSegment==0?p1[axis]-p0[axis]
+                    :0.5f*(p1[axis]-before[axis]);
+                const float m1=nearestSegment+2>=path.size()?p1[axis]-p0[axis]
+                    :0.5f*(after[axis]-p0[axis]);
+                center[axis]=h00*p0[axis]+h10*m0+h01*p1[axis]+h11*m1;
+                tangent[axis]=d00*p0[axis]+d10*m0+d01*p1[axis]+d11*m1;
+            }
+        };
+        std::array<float,3> center{},tangent{};
+        for(int refinement=0;refinement<2;++refinement)
+        {
+            evalCenterline(nearestProjection,center,tangent);
+            const float derivativeSquared=tangent[0]*tangent[0]+tangent[1]*tangent[1];
+            if(!(derivativeSquared>1.0e-10f))return std::numeric_limits<float>::infinity();
+            const float offsetX=center[0]-x,offsetY=center[1]-y;
+            nearestProjection=std::clamp(nearestProjection
+                -(offsetX*tangent[0]+offsetY*tangent[1])/derivativeSquared,0.0f,1.0f);
+        }
+        evalCenterline(nearestProjection,center,tangent);
+        const float tangentLength=std::sqrt(tangent[0]*tangent[0]
+            +tangent[1]*tangent[1]+tangent[2]*tangent[2]);
+        if(!(tangentLength>1.0e-8f))return std::numeric_limits<float>::infinity();
+        for(float& component:tangent)component/=tangentLength;
+        const float horizontalLength=std::sqrt(tangent[0]*tangent[0]
+            +tangent[1]*tangent[1]);
+        if(!(horizontalLength>1.0e-8f))return std::numeric_limits<float>::infinity();
+        const std::array<float,3> side={-tangent[1]/horizontalLength,
+            tangent[0]/horizontalLength,0.0f};
+        const std::array<float,3> up={-tangent[2]*side[1],tangent[2]*side[0],
+            tangent[0]*side[1]-tangent[1]*side[0]};
+        const std::array<float,3> relative={x-center[0],y-center[1],z-center[2]};
+        const auto dot=[&](const std::array<float,3>& axis)
+        {return relative[0]*axis[0]+relative[1]*axis[1]+relative[2]*axis[2];};
+        const float lateral=dot(side),vertical=dot(up);
+        if((nearestSegment==0&&nearestProjection<=0.0f)
+            ||(nearestSegment+2==path.size()&&nearestProjection>=1.0f))
+            return StampRoundedBoxSdf(dot(tangent),lateral,vertical,
+                {halfThickness+round,halfWidth,halfThickness},round);
+        const float qSide=std::abs(lateral)-halfWidth+round;
+        const float qUp=std::abs(vertical)-halfThickness+round;
+        const float outside=std::sqrt(std::max(qSide,0.0f)*std::max(qSide,0.0f)
+            +std::max(qUp,0.0f)*std::max(qUp,0.0f));
+        return outside+std::min(std::max(qSide,qUp),0.0f)-round;
+    }
     float StampSdf(const FStampRuntime& stamp,float x,float y,float z) const
     {
         float localX=x-stamp.positionVoxels[0];
@@ -7161,6 +7290,11 @@ private:
             break;
         case VoxelForgeCore::ResolvedSdfStampKindV1::fillSweptDeckSegment:
         {
+            if(!stamp.sweepPathVoxels.empty())
+            {
+                distance=StampContinuousSweptDeckSdf(stamp,x,y,z);
+                break;
+            }
             std::array<float,3> tangent{},side{},up{},delta{};
             float lengthSquared=0.0f,horizontalSquared=0.0f;
             for(std::size_t axis=0;axis<3;++axis)
@@ -7199,6 +7333,15 @@ private:
 
     static double StampAbsMinimum(double minimum,double maximum)
     {return minimum<=0.0&&maximum>=0.0?0.0:std::min(std::abs(minimum),std::abs(maximum));}
+    static bool UsesCoarsePillarProxy(const FStampRuntime& stamp,std::int32_t sampleStep)
+    {
+        if(!stamp.record||stamp.record->kind
+                !=VoxelForgeCore::ResolvedSdfStampKindV1::fillPillar
+            ||sampleStep<=0||stamp.irregularityAmplitudeVoxels>0.0f)return false;
+        return static_cast<float>(sampleStep)>std::min(stamp.halfExtentsVoxels[0],
+                stamp.halfExtentsVoxels[1])
+            ||static_cast<float>(sampleStep)>stamp.halfExtentsVoxels[2];
+    }
     static double StampRoundedBoxSdfDouble(const std::array<double,3>& absolute,
         const std::array<double,3>& halfSize,double rounding)
     {
@@ -7300,6 +7443,7 @@ private:
             if(index>=StampRuntime.size())return;
             const auto& runtime=StampRuntime[index];const auto& record=*runtime.record;
             if(record.strateIndex!=bound->StrateIndex)return;
+            if(UsesCoarsePillarProxy(runtime,CurrentStampSamplingStep()))return;
             for(std::size_t axis=0;axis<3;++axis)
                 if(worldMicrometres[axis]<record.boundsMinimumMicrometres[axis]
                     ||worldMicrometres[axis]>record.boundsMaximumMicrometres[axis])return;
@@ -7317,6 +7461,154 @@ private:
                 apply(static_cast<std::uint32_t>(index));
         return composed;
     }
+
+public:
+    std::uint32_t AppendCoarsePillarProxies(FVoxelMeshData& mesh,
+        const FIntVector& tileOrigin,std::int32_t tileExtent,std::int32_t sampleStep) const
+    {
+        if(!Owner||Owner->CoreVoxelSizeMicrons==0||tileExtent<=0||sampleStep<=0
+            ||StampRuntime.empty())return 0;
+        constexpr int32 sideCount=24;
+        constexpr double TwoPi=6.2831853071795864769;
+        const int32 originalVertexCount=mesh.Vertices.Num();
+        const int32 originalSurfaceVertices=std::clamp(mesh.NumSurfaceVertices,0,
+            originalVertexCount);
+        const bool hasNormals=mesh.Normals.Num()==originalVertexCount;
+        const bool hasUvs=mesh.UVs.Num()==originalVertexCount;
+        const bool hasColors=mesh.Colors.Num()==originalVertexCount;
+        const double voxelCentimetres=Owner->CoreVoxelSizeMicrons/10000.0;
+        const std::int64_t tileMinimum[3]={tileOrigin.X,tileOrigin.Y,tileOrigin.Z};
+        const std::int64_t tileMaximum[3]={static_cast<std::int64_t>(tileOrigin.X)+tileExtent,
+            static_cast<std::int64_t>(tileOrigin.Y)+tileExtent,
+            static_cast<std::int64_t>(tileOrigin.Z)+tileExtent};
+        std::vector<int32> proxyIndices;
+        std::uint32_t proxyCount=0;
+        const auto addVertex=[&](const FVector& position,const FVector& normal,
+            const FVector2f& uv)
+        {
+            const int32 index=mesh.Vertices.Add(position);
+            if(hasNormals)mesh.Normals.Add(normal);
+            if(hasUvs)mesh.UVs.Add(uv);
+            if(hasColors)mesh.Colors.Add(FColor::White);
+            return index;
+        };
+        for(const auto& stamp:StampRuntime)
+        {
+            if(!UsesCoarsePillarProxy(stamp,sampleStep))continue;
+            const auto& center=stamp.positionVoxels;
+            if(center[0]<tileMinimum[0]||center[0]>=tileMaximum[0]
+                ||center[1]<tileMinimum[1]||center[1]>=tileMaximum[1]
+                ||center[2]<tileMinimum[2]||center[2]>=tileMaximum[2])continue;
+            const double radiusX=stamp.halfExtentsVoxels[0];
+            const double radiusY=stamp.halfExtentsVoxels[1];
+            const double bottomVoxel=center[2]-stamp.halfExtentsVoxels[2]-1.0;
+            const double topVoxel=center[2]+stamp.halfExtentsVoxels[2];
+            const auto point=[&](double angle,double z)
+            {
+                return FVector((center[0]+radiusX*std::cos(angle))*voxelCentimetres,
+                    (center[1]+radiusY*std::sin(angle))*voxelCentimetres,
+                    z*voxelCentimetres);
+            };
+            const int32 capTopCenter=addVertex(FVector(center[0]*voxelCentimetres,
+                center[1]*voxelCentimetres,topVoxel*voxelCentimetres),
+                FVector(0.0,0.0,1.0),FVector2f(0.5f,0.5f));
+            const int32 capBottomCenter=addVertex(FVector(center[0]*voxelCentimetres,
+                center[1]*voxelCentimetres,bottomVoxel*voxelCentimetres),
+                FVector(0.0,0.0,-1.0),FVector2f(0.5f,0.5f));
+            for(int32 sideIndex=0;sideIndex<sideCount;++sideIndex)
+            {
+                const double u0=static_cast<double>(sideIndex)/sideCount;
+                const double u1=static_cast<double>(sideIndex+1)/sideCount;
+                const double a0=TwoPi*u0,a1=TwoPi*u1;
+                const FVector n0=FVector(std::cos(a0)/radiusX,
+                    std::sin(a0)/radiusY,0.0).GetSafeNormal();
+                const FVector n1=FVector(std::cos(a1)/radiusX,
+                    std::sin(a1)/radiusY,0.0).GetSafeNormal();
+                const int32 bottomA=addVertex(point(a0,bottomVoxel),n0,FVector2f(u0,0.0f));
+                const int32 bottomB=addVertex(point(a1,bottomVoxel),n1,FVector2f(u1,0.0f));
+                const int32 topB=addVertex(point(a1,topVoxel),n1,FVector2f(u1,1.0f));
+                const int32 topA=addVertex(point(a0,topVoxel),n0,FVector2f(u0,1.0f));
+                proxyIndices.insert(proxyIndices.end(),{bottomA,bottomB,topB,
+                    bottomA,topB,topA});
+
+                const int32 topAIndex=addVertex(point(a0,topVoxel),FVector(0.0,0.0,1.0),
+                    FVector2f(static_cast<float>(0.5+0.5*std::cos(a0)),
+                        static_cast<float>(0.5+0.5*std::sin(a0))));
+                const int32 topBIndex=addVertex(point(a1,topVoxel),FVector(0.0,0.0,1.0),
+                    FVector2f(static_cast<float>(0.5+0.5*std::cos(a1)),
+                        static_cast<float>(0.5+0.5*std::sin(a1))));
+                proxyIndices.insert(proxyIndices.end(),{capTopCenter,topAIndex,topBIndex});
+
+                const int32 bottomAIndex=addVertex(point(a0,bottomVoxel),FVector(0.0,0.0,-1.0),
+                    FVector2f(static_cast<float>(0.5+0.5*std::cos(a0)),
+                        static_cast<float>(0.5+0.5*std::sin(a0))));
+                const int32 bottomBIndex=addVertex(point(a1,bottomVoxel),FVector(0.0,0.0,-1.0),
+                    FVector2f(static_cast<float>(0.5+0.5*std::cos(a1)),
+                        static_cast<float>(0.5+0.5*std::sin(a1))));
+                proxyIndices.insert(proxyIndices.end(),
+                    {capBottomCenter,bottomBIndex,bottomAIndex});
+            }
+            ++proxyCount;
+        }
+        if(proxyIndices.empty())return 0;
+        const int32 proxyVertexCount=mesh.Vertices.Num()-originalVertexCount;
+        const auto insertProxyVertices=[&](auto& values)
+        {
+            if(values.Num()!=originalVertexCount+proxyVertexCount)return;
+            using FArray=std::remove_reference_t<decltype(values)>;
+            FArray reordered;
+            reordered.Reserve(values.Num());
+            for(int32 index=0;index<originalSurfaceVertices;++index)
+                reordered.Add(values[index]);
+            for(int32 index=originalVertexCount;index<values.Num();++index)
+                reordered.Add(values[index]);
+            for(int32 index=originalSurfaceVertices;index<originalVertexCount;++index)
+                reordered.Add(values[index]);
+            values=MoveTemp(reordered);
+        };
+        insertProxyVertices(mesh.Vertices);
+        if(hasNormals)insertProxyVertices(mesh.Normals);
+        if(hasUvs)insertProxyVertices(mesh.UVs);
+        if(hasColors)insertProxyVertices(mesh.Colors);
+
+        const int32 oldTriangleCount=mesh.Triangles.Num()/3;
+        const int32 ceilingStart=std::max(0,mesh.Triangles.Num()-mesh.NumCeilingTriangles*3);
+        const int32 groundTriangleCount=ceilingStart/3;
+        const int32 proxyTriangleCount=static_cast<int32>(proxyIndices.size()/3);
+        TArray<int32> mergedIndices;
+        mergedIndices.Reserve(mesh.Triangles.Num()+static_cast<int32>(proxyIndices.size()));
+        for(int32 index=0;index<ceilingStart;++index)
+        {
+            const int32 oldIndex=mesh.Triangles[index];
+            mergedIndices.Add(oldIndex>=originalSurfaceVertices
+                ?oldIndex+proxyVertexCount:oldIndex);
+        }
+        for(const int32 index:proxyIndices)
+            mergedIndices.Add(originalSurfaceVertices+index-originalVertexCount);
+        for(int32 index=ceilingStart;index<mesh.Triangles.Num();++index)
+        {
+            const int32 oldIndex=mesh.Triangles[index];
+            mergedIndices.Add(oldIndex>=originalSurfaceVertices
+                ?oldIndex+proxyVertexCount:oldIndex);
+        }
+        mesh.Triangles=MoveTemp(mergedIndices);
+
+        TArray<uint8> mergedMasks;
+        mergedMasks.Reserve(oldTriangleCount+proxyTriangleCount);
+        for(int32 triangle=0;triangle<groundTriangleCount;++triangle)
+            mergedMasks.Add(mesh.TriangleSkirtFaceMasks.IsValidIndex(triangle)
+                ?mesh.TriangleSkirtFaceMasks[triangle]:0);
+        for(int32 triangle=0;triangle<proxyTriangleCount;++triangle)mergedMasks.Add(0);
+        if(groundTriangleCount<oldTriangleCount)
+            for(int32 triangle=groundTriangleCount;triangle<oldTriangleCount;++triangle)
+                mergedMasks.Add(mesh.TriangleSkirtFaceMasks.IsValidIndex(triangle)
+                    ?mesh.TriangleSkirtFaceMasks[triangle]:0);
+        mesh.TriangleSkirtFaceMasks=MoveTemp(mergedMasks);
+        mesh.NumSurfaceVertices=originalSurfaceVertices+proxyVertexCount;
+        return proxyCount;
+    }
+
+private:
     float ApplyResolvedCavernGraph(float density,float X,float Y,float Z,
         float* nativeFloorSupport=nullptr) const
     {