Agent Skills

ue-procedural-generation

gamesquodsoler

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npx skills add https://github.com/quodsoler/unreal-engine-skills --skill ue-procedural-generation
SKILL.md

UE Procedural Generation

Target engine: UE 5.8. APIs below are verified against the 5.8 headers; older forms are listed under "Deprecated — do not use".

Covers the PCG framework (plugin PCG at Engine/Plugins/PCG, enabled by default, Build.cs module PCG), runtime mesh building with UProceduralMeshComponent (plugin ProceduralMeshComponent, module ProceduralMeshComponent) and UDynamicMeshComponent + Geometry Script (modules GeometryFramework and GeometryScriptingCore), instancing with UInstancedStaticMeshComponent/UHierarchicalInstancedStaticMeshComponent, spline-driven placement, and deterministic noise/random from Core.

Context

Read .agents/ue-project-context.md if it exists (module names, conventions, enabled plugins, GAS/networking setup). Do not stop if it is missing.

Identify the area from the request and the codebase. Ask only when two plausible readings would produce different code.

Request is about… Go to
Enabling PCG, module/plugin wiring PCG setup
Driving generation from an actor, runtime generation, partitioning PCG component and runtime generation
Reading/writing points inside a graph Point data
Writing a new PCG node in C++ Custom PCG node in C++
Which node does X, pin labels, node settings fields PCG node reference
Building triangles at runtime ProceduralMeshComponent
Boolean ops, primitives, baking to a static mesh Dynamic Mesh and Geometry Script
Thousands of repeated meshes Instanced static meshes
Roads, rivers, fences, cables Splines
Heightfields, scatter, reproducible results Noise and deterministic random
Marching cubes, BSP dungeons, WFC, Poisson disc Procedural mesh patterns

PCG setup

// MyGame.Build.cs
PublicDependencyModuleNames.AddRange(new string[] { "Core", "CoreUObject", "Engine", "PCG" });

{ "Name": "PCG", "Enabled": true }
Class Header Role
UPCGComponent PCGComponent.h Actor component that owns a graph and drives generation
UPCGGraph PCGGraph.h Graph asset: nodes, edges, UserParameters
UPCGGraphInstance PCGGraph.h Graph instance with per-instance parameter overrides
UPCGGraphInterface PCGGraph.h Common base of graph and graph instance
UPCGSettings PCGSettings.h Node settings base class
IPCGElement PCGElement.h The executable half of a node
FPCGContext PCGContext.h Per-execution state: InputData, OutputData, Node, ExecutionSource
UPCGBasePointData Data/PCGBasePointData.h Abstract point collection
UPCGPointArrayData Data/PCGPointArrayData.h Structure-of-arrays point data
UPCGSubsystem Subsystems/PCGSubsystem.h Scheduling, partitioning, runtime generation
APCGVolume PCGVolume.h Volume actor carrying a UPCGComponent

PCG component and runtime generation

#include "PCGComponent.h"
#include "PCGGraph.h"

void AMyGenerator::StartGeneration(UPCGGraphInterface* Graph, int32 InSeed)
{
    UPCGComponent* PCG = FindComponentByClass<UPCGComponent>();
    if (!PCG)
    {
        return;
    }

    PCG->Seed = InSeed;
    PCG->bActivated = true;
    PCG->SetGraph(Graph);      // NetMulticast, Reliable
    PCG->Generate(/*bForce=*/true);  // NetMulticast, Reliable
}
Call Replication Use for
Generate(bool bForce) / Cleanup(bool bRemoveComponents) NetMulticast, Reliable Server-driven generation that must appear on clients
GenerateLocal(bool bForce) / CleanupLocal(bool bRemoveComponents) none Client-side or single-player generation
NotifyPropertiesChangedFromBlueprint() none Mark dirty and conditionally regenerate after editing exposed properties
CancelGeneration() none Abort an in-flight generation
GetGeneratedGraphOutput() none Read back the FPCGDataCollection the graph produced

EPCGComponentGenerationTrigger (PCGComponent.h:77): GenerateOnLoad, GenerateOnDemand, GenerateAtRuntime.

Partitioning and runtime generation:

  • SetIsPartitioned(bool) / IsPartitioned() back the bIsComponentPartitioned property; partitioned components dispatch work to local components on a grid.
  • GenerateAtRuntime hands the component to the runtime-gen scheduler. Tune it with SchedulingPolicyClass / SchedulingPolicy (UPCGSchedulingPolicyBase) and bOverrideGenerationRadii + GenerationRadii (FPCGRuntimeGenerationRadii).
  • Scheduler CVars: pcg.RuntimeGeneration.Enable, pcg.RuntimeGeneration.NumGeneratingComponents, pcg.RuntimeGeneration.GlobalRadiusMultiplier, pcg.RuntimeGeneration.EnablePooling, pcg.RuntimeGeneration.BasePoolSize, pcg.RuntimeGeneration.FramesBeforeFirstGenerate, pcg.RuntimeGeneration.EnableChangeDetection, pcg.RuntimeGeneration.EnableDebugging.
  • UPCGSubsystem::GetSubsystemForCurrentWorld() returns the subsystem; RefreshAllComponentsFiltered(Filter, ChangeType) forces a refresh of a subset (WITH_EDITOR only, Subsystems/PCGSubsystem.h:227-230).

Hierarchical generation lives on UPCGGraph: bUseHierarchicalGeneration, HiGenGridSize (EPCGHiGenGrid::Grid4 … Grid2048, plus Unbounded), HiGenGridSizeMultiplier, bUse2DGrid.

Graph parameters are an FInstancedPropertyBag UserParameters on UPCGGraph, read and written through UPCGGraphInterface:

TValueOrError<double, EPropertyBagResult> Result = Graph->GetGraphParameter<double>(TEXT("SpawnRadius"));
if (Result.HasValue())
{
    const double Radius = Result.GetValue();
    Graph->SetGraphParameter<double>(TEXT("SpawnRadius"), Radius * 2.0);
}

Point data

Point collections are UPCGBasePointData. UPCGPointArrayData is the structure-of-arrays implementation; UPCGPointData is the array-of-FPCGPoint implementation kept for compatibility. Allocate through the context so the project-configured class is used:

UPCGBasePointData* Points = FPCGContext::NewPointData_AnyThread(Context);

Never iterate GetPoints()/GetMutablePoints() in new code — that only exists on UPCGPointData and forces a conversion. Read and write through value ranges instead:

#include "Data/PCGBasePointData.h"

const FConstPCGPointValueRanges ReadRanges(InputPoints);
FPCGPointValueRanges WriteRanges(OutputPoints, /*bAllocate=*/false);

WriteRanges.TransformRange[Index] = ReadRanges.TransformRange[Index];
WriteRanges.DensityRange[Index]   = ReadRanges.DensityRange[Index];

Per-point native properties (EPCGPointNativeProperties in PCGPointPropertiesTraits.h): Transform, Density, BoundsMin, BoundsMax, Color, Steepness, Seed, MetadataEntry, plus All and AllProperties. Sizing and allocation:

Output->SetNumPoints(Input->GetNumPoints(), /*bInitializeValues=*/false);
Output->AllocateProperties(Input->GetAllocatedProperties() | EPCGPointNativeProperties::Density);
Output->CopyUnallocatedPropertiesFrom(Input);

Other data types: UPCGSpatialData (base), UPCGSplineData, UPCGLandscapeData, UPCGVolumeData, UPCGTextureData, UPCGPrimitiveData, UPCGDynamicMeshData, and UPCGParamData for attribute sets. UPCGSpatialData::ToBasePointData(FPCGContext*, const FBox&) discretizes any spatial data into points.

Custom PCG node in C++

A node is a UPCGSettings subclass plus an IPCGElement. Settings hold data; the element is const and stateless and reads everything from FPCGContext.

// MyPCGJitter.h
#pragma once

#include "PCGElement.h"
#include "PCGSettings.h"
#include "MyPCGJitter.generated.h"

UCLASS(BlueprintType, ClassGroup = (Procedural))
class MYGAME_API UMyPCGJitterSettings : public UPCGSettings
{
    GENERATED_BODY()

public:
#if WITH_EDITOR
    virtual FName GetDefaultNodeName() const override { return FName(TEXT("MyJitter")); }
    virtual FText GetDefaultNodeTitle() const override { return NSLOCTEXT("MyPCGJitter", "NodeTitle", "My Jitter"); }
    virtual EPCGSettingsType GetType() const override { return EPCGSettingsType::PointOps; }
#endif

    UPROPERTY(BlueprintReadWrite, EditAnywhere, Category = Settings, meta = (PCG_Overridable))
    double JitterRadius = 100.0;

protected:
    virtual TArray<FPCGPinProperties> InputPinProperties() const override { return Super::DefaultPointInputPinProperties(); }
    virtual TArray<FPCGPinProperties> OutputPinProperties() const override { return Super::DefaultPointOutputPinProperties(); }
    virtual FPCGElementPtr CreateElement() const override;
};

class FMyPCGJitterElement : public IPCGElement
{
protected:
    virtual bool ExecuteInternal(FPCGContext* Context) const override;
    virtual bool IsCacheable(const UPCGSettings* InSettings) const override { return true; }
    virtual bool CanExecuteOnlyOnMainThread(FPCGContext* Context) const override { return false; }
    virtual bool SupportsBasePointDataInputs(FPCGContext* InContext) const override { return true; }
    virtual EPCGElementExecutionLoopMode ExecutionLoopMode(const UPCGSettings* Settings) const override { return EPCGElementExecutionLoopMode::SinglePrimaryPin; }
};

// MyPCGJitter.cpp
#include "MyPCGJitter.h"

#include "PCGContext.h"
#include "Data/PCGBasePointData.h"
#include "Data/PCGSpatialData.h"
#include "Math/RandomStream.h"

FPCGElementPtr UMyPCGJitterSettings::CreateElement() const
{
    return MakeShared<FMyPCGJitterElement>();
}

bool FMyPCGJitterElement::ExecuteInternal(FPCGContext* Context) const
{
    const UMyPCGJitterSettings* Settings = Context->GetInputSettings<UMyPCGJitterSettings>();
    check(Settings);

    const double JitterRadius = Settings->JitterRadius;
    const TArray<FPCGTaggedData> Inputs = Context->InputData.GetInputsByPin(PCGPinConstants::DefaultInputLabel);
    TArray<FPCGTaggedData>& Outputs = Context->OutputData.TaggedData;

    for (const FPCGTaggedData& Input : Inputs)
    {
        const UPCGSpatialData* SpatialData = Cast<UPCGSpatialData>(Input.Data);
        if (!SpatialData)
        {
            continue;
        }

        const UPCGBasePointData* InputPoints = SpatialData->ToBasePointData(Context);
        if (!InputPoints)
        {
            continue;
        }

        UPCGBasePointData* OutputPoints = FPCGContext::NewPointData_AnyThread(Context);
        OutputPoints->InitializeFromDataWithParams(FPCGInitializeFromDataParams(InputPoints));
        OutputPoints->SetNumPoints(InputPoints->GetNumPoints(), /*bInitializeValues=*/false);
        OutputPoints->AllocateProperties(InputPoints->GetAllocatedProperties() | EPCGPointNativeProperties::Transform);
        OutputPoints->CopyUnallocatedPropertiesFrom(InputPoints);

        const FConstPCGPointValueRanges ReadRanges(InputPoints);
        FPCGPointValueRanges WriteRanges(OutputPoints, /*bAllocate=*/false);

        for (int32 Index = 0; Index < InputPoints->GetNumPoints(); ++Index)
        {
            WriteRanges.SetFromValueRanges(Index, ReadRanges, Index);

            const FRandomStream Stream(ReadRanges.SeedRange[Index]);
            FTransform Jittered = ReadRanges.TransformRange[Index];
            Jittered.AddToTranslation(Stream.VRand() * (Stream.FRand() * JitterRadius));
            WriteRanges.TransformRange[Index] = Jittered;
        }

        FPCGTaggedData& Output = Outputs.Add_GetRef(Input);
        Output.Data = OutputPoints;
    }

    return true;
}

Rules that fall out of the headers:

  • SupportsBasePointDataInputs returning false (the default) makes PCG convert every input to UPCGPointData before your element runs. Return true and use value ranges.
  • IsCacheable must return false if the node spawns actors or components, or reads untracked data.
  • CanExecuteOnlyOnMainThread returning true serializes the node onto the game thread; keep it false unless you touch UWorld or components.
  • Long loops belong in FPCGAsync::AsyncProcessingRangeEx(&Context->AsyncState, NumIterations, Initialize, ProcessRange, MoveDataRange, Finished, bEnableTimeSlicing) (Helpers/PCGAsync.h), which time-slices and multithreads.
  • Pin labels come from PCGPinConstants::DefaultInputLabel ("In"), DefaultOutputLabel ("Out"), DefaultParamsLabel ("Overrides"), DefaultExecutionDependencyLabel.
  • Blueprint nodes derive from UPCGBlueprintBaseElement and override the Execute(const FPCGDataCollection&, FPCGDataCollection&) BlueprintNativeEvent; seed helpers are GetSeedWithContext(GetContextHandle()) and GetRandomStreamWithContext(GetContextHandle()).

See PCG node reference for node settings classes, pin behaviour, metadata attributes and GPU nodes.

ProceduralMeshComponent

Triangle-level control at runtime. No Nanite support, no automatic LODs.

PublicDependencyModuleNames.Add("ProceduralMeshComponent");

// Full form (ProceduralMeshComponent.h:190) also takes UV1, UV2 and UV3 between UV0 and VertexColors
// UV0-only convenience overload (ProceduralMeshComponent.h:193)
void CreateMeshSection_LinearColor(int32 SectionIndex, const TArray<FVector>& Vertices, const TArray<int32>& Triangles,
    const TArray<FVector>& Normals, const TArray<FVector2D>& UV0, const TArray<FLinearColor>& VertexColors,
    const TArray<FProcMeshTangent>& Tangents, bool bCreateCollision, bool bSRGBConversion = false);

void UpdateMeshSection_LinearColor(int32 SectionIndex, const TArray<FVector>& Vertices, const TArray<FVector>& Normals,
    const TArray<FVector2D>& UV0, const TArray<FLinearColor>& VertexColors,
    const TArray<FProcMeshTangent>& Tangents, bool bSRGBConversion = true);   // true here, false on Create (ProceduralMeshComponent.h:230)

void ClearMeshSection(int32 SectionIndex);
void ClearAllMeshSections();
void SetMeshSectionVisible(int32 SectionIndex, bool bNewVisibility);
int32 GetNumSections() const;
void AddCollisionConvexMesh(TArray<FVector> ConvexVerts);
void ClearCollisionConvexMeshes();

Materials come from UMeshComponent::SetMaterial(int32 ElementIndex, UMaterialInterface* Material) — one material slot per section index.

Collision:

  • bUseComplexAsSimpleCollision (default true) uses the rendered triangles for collision. Accurate, expensive, and cannot be simulated — set it to false and feed AddCollisionConvexMesh when the mesh must be dynamic.
  • bUseAsyncCooking moves physics cooking off the game thread. Collision lags a frame or more behind the visual mesh; use it for far-away streamed geometry.

UpdateMeshSection_LinearColor moves existing vertices and refreshes collision, but cannot change vertex or triangle count — call CreateMeshSection_LinearColor when topology changes. Build the arrays on a worker thread, then call the component on the game thread; see async mesh generation.

Dynamic Mesh and Geometry Script

UDynamicMeshComponent (GeometryFramework, header Components/DynamicMeshComponent.h) plus the Geometry Script libraries (GeometryScriptingCore) are the modern path: boolean operations, remeshing, normals recomputation, and baking to a UStaticMesh asset (editor only — CopyMeshToStaticMesh errors "Not currently supported at Runtime" outside WITH_EDITOR, MeshAssetFunctions.cpp:471).

PublicDependencyModuleNames.AddRange(new string[] { "GeometryFramework", "GeometryScriptingCore" });
Library Representative functions
UGeometryScriptLibrary_MeshPrimitiveFunctions AppendBox, AppendSphereLatLong, AppendSphereBox, AppendCapsule, AppendBoxWithCollision
UGeometryScriptLibrary_MeshBooleanFunctions ApplyMeshBoolean(TargetMesh, TargetTransform, ToolMesh, ToolTransform, Operation, Options, Debug)
UGeometryScriptLibrary_MeshDeformFunctions ApplyPerlinNoiseToMesh2(TargetMesh, Selection, Options, Debug)
UGeometryScriptLibrary_MeshNormalsFunctions RecomputeNormals(TargetMesh, CalculateOptions, bDeferChangeNotifications, Debug), SetPerFaceNormals
UGeometryScriptLibrary_StaticMeshFunctions CopyMeshToStaticMesh, CopyMeshFromStaticMeshV2

A worked example is in dynamic mesh with Geometry Script.

Collision on UDynamicMeshComponent: EnableComplexAsSimpleCollision(), SetComplexAsSimpleCollisionEnabled(bool bEnabled, bool bImmediateUpdate), SetSimpleCollisionShapes(const FKAggregateGeom&, bool bUpdateCollision), bDeferCollisionUpdates + UpdateCollision(bool bOnlyIfPending). ADynamicMeshActor ships a component at the root via GetDynamicMeshComponent().

Instanced static meshes

UInstancedStaticMeshComponent UHierarchicalInstancedStaticMeshComponent
Header Components/InstancedStaticMeshComponent.h Components/HierarchicalInstancedStaticMeshComponent.h
Best for Small, frequently mutated sets Large, mostly static sets
Culling Start/end cull distance Hierarchical tree plus cull distance
Removal Cheap Triggers a tree rebuild (bAutoRebuildTreeOnInstanceChanges, BuildTreeIfOutdated) 
virtual int32 AddInstance(const FTransform& InstanceTransform, bool bWorldSpace = false);
virtual TArray<int32> AddInstances(const TArray<FTransform>& InstanceTransforms, bool bShouldReturnIndices,
    bool bWorldSpace = false, bool bUpdateNavigation = true);
virtual bool UpdateInstanceTransform(int32 InstanceIndex, const FTransform& NewInstanceTransform,
    bool bWorldSpace = false, bool bMarkRenderStateDirty = false, bool bTeleport = false);
virtual bool BatchUpdateInstancesTransforms(int32 StartInstanceIndex, const TArray<FTransform>& NewInstancesTransforms,
    bool bWorldSpace = false, bool bMarkRenderStateDirty = false, bool bTeleport = false);
bool GetInstanceTransform(int32 InstanceIndex, FTransform& OutInstanceTransform, bool bWorldSpace = false) const;
virtual bool RemoveInstance(int32 InstanceIndex);
virtual bool RemoveInstances(const TArray<int32>& InstancesToRemove);
virtual void PreAllocateInstancesMemory(int32 AddedInstanceCount);
int32 GetNumInstances() const;
virtual void SetNumCustomDataFloats(int32 InNumCustomDataFloats);
virtual bool SetCustomDataValue(int32 InstanceIndex, int32 CustomDataIndex, float CustomDataValue,
    bool bMarkRenderStateDirty = false);
void SetCullDistances(int32 StartCullDistance, int32 EndCullDistance);
const TArray<FBodyInstance*>& GetInstanceBodies() const;

Per-instance floats set with SetNumCustomDataFloats / SetCustomDataValue are read in materials through the PerInstanceCustomData node. Cull properties: InstanceStartCullDistance, InstanceEndCullDistance, InstanceLODDistanceScale, bUseGpuLodSelection.

Batch large populations: PreAllocateInstancesMemory first, build the whole TArray<FTransform>, then one AddInstances call. A full seeded scatter that traces onto terrain and fills per-instance custom data is in vegetation scatter.

Foliage (module Foliage): painted foliage lives on AInstancedFoliageActor backed by UFoliageInstancedStaticMeshComponent; simulation-driven placement uses UProceduralFoliageComponent with a UProceduralFoliageSpawner. PCG's Static Mesh Spawner node is usually the better fit for graph-driven scatter.

Splines

// USplineComponent — Components/SplineComponent.h
void AddSplinePoint(const FVector& Position, ESplineCoordinateSpace::Type CoordinateSpace, bool bUpdateSpline = true);
void SetSplinePoints(const TArray<FVector>& Points, ESplineCoordinateSpace::Type CoordinateSpace, bool bUpdateSpline = true);
void SetSplinePointType(int32 PointIndex, ESplinePointType::Type Type, bool bUpdateSpline = true);
void SetTangentsAtSplinePoint(int32 PointIndex, const FVector& InArriveTangent, const FVector& InLeaveTangent,
    ESplineCoordinateSpace::Type CoordinateSpace, bool bUpdateSpline = true);
void SetClosedLoop(bool bInClosedLoop, bool bUpdateSpline = true);
virtual void UpdateSpline();
float GetSplineLength() const;
FVector GetLocationAtDistanceAlongSpline(float Distance, ESplineCoordinateSpace::Type CoordinateSpace) const;
FTransform GetTransformAtDistanceAlongSpline(float Distance, ESplineCoordinateSpace::Type CoordinateSpace,
    bool bUseScale = false) const;
void GetLocationAndTangentAtSplinePoint(int32 PointIndex, FVector& Location, FVector& Tangent,
    ESplineCoordinateSpace::Type CoordinateSpace) const;
float FindInputKeyClosestToWorldLocation(const FVector& WorldLocation) const;

ESplinePointType::Type: Linear, Curve, Constant, CurveClamped, CurveCustomTangent. ESplineCoordinateSpace::Type: Local, World.

Pass bUpdateSpline = false while batching edits and call UpdateSpline() once — each update rebuilds the reparameterization table. Distance along the spline is arc length; the input key is not, so always space instances by distance.

// USplineMeshComponent — one deformed mesh per spline segment
void AMyRoadActor::BuildSegment(USplineComponent* Spline, UStaticMesh* RoadMesh, int32 SegmentIndex)
{
    USplineMeshComponent* SegmentMesh = NewObject<USplineMeshComponent>(this);
    SegmentMesh->SetMobility(EComponentMobility::Movable);
    SegmentMesh->SetupAttachment(Spline);
    SegmentMesh->SetStaticMesh(RoadMesh);
    SegmentMesh->SetForwardAxis(ESplineMeshAxis::X, /*bUpdateMesh=*/false);
    SegmentMesh->RegisterComponent();

    FVector StartPos, StartTangent, EndPos, EndTangent;
    Spline->GetLocationAndTangentAtSplinePoint(SegmentIndex, StartPos, StartTangent, ESplineCoordinateSpace::Local);
    Spline->GetLocationAndTangentAtSplinePoint(SegmentIndex + 1, EndPos, EndTangent, ESplineCoordinateSpace::Local);
    SegmentMesh->SetStartAndEnd(StartPos, StartTangent, EndPos, EndTangent, /*bUpdateMesh=*/true);
}

Noise and deterministic random

#include "Math/RandomStream.h"
#include "Math/UnrealMathUtility.h"

// All three return a continuous value in [-1, 1]
float SampleNoise(const FVector& Position, float Frequency)
{
    const float N1 = FMath::PerlinNoise1D(Position.X * Frequency);
    const float N2 = FMath::PerlinNoise2D(FVector2D(Position.X, Position.Y) * Frequency);
    const float N3 = FMath::PerlinNoise3D(Position * Frequency);
    return (N1 + N2 + N3) / 3.f;
}

FTransform MakeSeededTransform(int32 Seed, const FVector& Origin)
{
    FRandomStream Stream(Seed);
    const float Unit = Stream.GetFraction();              // [0, 1), same as FRand()
    const double Offset = Stream.FRandRange(-50.0, 50.0);
    const int32 Variant = Stream.RandRange(0, 3);         // inclusive on both ends
    const FVector Direction = Stream.VRand();             // uniform unit vector

    return FTransform(FRotator(0.0, Unit * 360.0, 0.0),
                      Origin + Direction * Offset,
                      FVector(1.0 + Variant * 0.1));
}

Determinism rules:

  • Derive every stream from one project seed. FRandomStream::Initialize(int32) resets a stream; GetCurrentSeed() / GetInitialSeed() let you checkpoint one.
  • Inside PCG, seed per point from ReadRanges.SeedRange[Index], or take the node seed from FPCGContext::GetSeed(). Do not call FMath::Rand.
  • For networked generation, replicate the seed (GameState or spawn parameter) and use Generate(bForce); GenerateLocal never replicates.
  • Sort inputs before consuming them when order affects the result — iteration order of gathered actor data is not guaranteed stable.

Octave/fractal noise, Poisson disc sampling, marching cubes, BSP dungeons and wave function collapse are implemented in procedural mesh patterns.

Deprecated — do not use

Do not emit Use in 5.8 Source
FSimplePCGElement IPCGElement UE_DEPRECATED(5.4) in PCGElement.h:271
IPCGElement::Initialize(const FPCGDataCollection&, TWeakObjectPtr<UPCGComponent>, const UPCGNode*) Initialize(const FPCGInitializeElementParams&) UE_DEPRECATED(5.6) in PCGElement.h:147
FPCGContext::SourceComponent FPCGContext::ExecutionSource UE_DEPRECATED(5.6) in PCGContext.h:122
FPCGContext::GetComponentName() GetExecutionSourceName() UE_DEPRECATED(5.6) in PCGContext.h:207
FPCGContext::Stack GetStack() UE_DEPRECATED(5.6) in PCGContext.h:147
UPCGSpatialData::IntersectWith/ProjectOn/UnionWith/Subtract/CopyInternal without a context overloads taking FPCGContext* UE_DEPRECATED(5.5) in Data/PCGSpatialData.h:208-280
ToPointData() (no context) ToBasePointData(FPCGContext*) / ToBasePointDataWithContext DeprecatedFunction in Data/PCGSpatialData.h:159
UPCGPointData::GetOctree() / IsOctreeDirty() GetPointOctree() / IsPointOctreeDirty() UE_DEPRECATED(5.6) in Data/PCGPointData.h:145,147
UPCGComponent::CleanupLocal(bRemoveComponents, bSave) CleanupLocal(bRemoveComponents) UE_DEPRECATED(5.6) in PCGComponent.h:236
UPCGComponent::GenerateLocal(..., EPCGHiGenGrid Grid, ...) overload taking a uint32 grid size UE_DEPRECATED(5.8) in PCGComponent.h:872
UPCGGraph::HiGenExponential / GetGridExponential() HiGenGridSizeMultiplier / GetGridSizeMultiplier() UE_DEPRECATED(5.8) in PCGGraph.h:866,872
UPCGGraph::bIsEditorOnly ShouldCook (FPerPlatformBool) UE_DEPRECATED(5.8) in PCGGraph.h:868
UPCGSettings::BP_GetTypeUnionOfIncidentEdges GetTypeUnionIDOfIncidentEdges UE_DEPRECATED(5.7) in PCGSettings.h:520
UInstancedStaticMeshComponent::InstanceBodies GetInstanceBodies() UE_DEPRECATED(5.8) in Components/InstancedStaticMeshComponent.h:524
UInstancedStaticMeshComponent::InitInstanceBody InstancePhysicsBodies UE_DEPRECATED(5.8) in Components/InstancedStaticMeshComponent.h:771
ApplyPerlinNoiseToMesh ApplyPerlinNoiseToMesh2 UE_DEPRECATED(5.7) in GeometryScript/MeshDeformFunctions.h:401
CopyMeshToStaticMesh without bUseSectionMaterials overload taking bUseSectionMaterials UE_DEPRECATED(5.5) in GeometryScript/MeshAssetFunctions.h:311

Common Mistakes

Iterating FPCGPoint arrays in a custom element: GetPoints() only exists on UPCGPointData, so PCG silently converts every input and you pay a full copy. Override SupportsBasePointDataInputs to return true and read FConstPCGPointValueRanges.

Forgetting AllocateProperties before writing: FPCGPointValueRanges built with bAllocate = false leaves unallocated ranges empty, so indexing them fails the checkf range check (Utils/PCGValueRange.h:139). Call SetNumPoints then AllocateProperties for every property you intend to write.

GenerateLocal in multiplayer: it is not a network function, so clients never generate. Use Generate(bool bForce) (NetMulticast, Reliable) and replicate the seed.

Generating from Tick: PCG generation schedules graph tasks. Use GenerateOnDemand and call Generate only when inputs change, or GenerateAtRuntime and let the scheduler budget it.

Caching a node that spawns actors: leaving IsCacheable at true for a node that creates actors or components produces duplicated or missing artifacts on regeneration. Return false.

Expecting UpdateMeshSection_LinearColor to change topology: it only rewrites existing vertices. Adding or removing triangles requires CreateMeshSection_LinearColor.

Clockwise triangle winding: front faces are counter-clockwise, so clockwise triangles vanish under back-face culling.

Calling AddSplinePoint with bUpdateSpline = true in a loop: each call rebuilds the whole reparameterization table. Pass false and call UpdateSpline() once.

Spacing instances by spline input key: the key is not proportional to arc length. Step by distance and use GetTransformAtDistanceAlongSpline.

bMarkRenderStateDirty = true on every instance update: each call re-uploads the instance buffer. Leave it false in the loop and call MarkRenderStateDirty() once.

Expecting Nanite from UProceduralMeshComponent: it has no Nanite path. Bake to a UStaticMesh in the editor with CopyMeshToStaticMesh (editor-only) or scatter Nanite static meshes with PCG and instanced components.

Related Skills

  • ue-actor-component-architecture — component construction, registration, attachment and lifecycle for the components created here
  • ue-physics-collision — collision profiles, body setup, complex vs simple collision, traces used to project scatter onto terrain
  • ue-materials-rendering — material instances, PerInstanceCustomData, Nanite and virtual texturing for generated geometry
  • ue-world-level-streaming — World Partition, data layers and HLODs that PCG partitioning and runtime generation build on
  • ue-async-threading — ParallelFor, Async, task graph and thread-safety rules for background mesh and point computation
  • ue-mass-entity — large agent populations, an alternative to instanced components for crowds
  • ue-data-assets-tables — data assets and data tables that drive generation parameters and mesh/prop tables
  • ue-niagara-effects — Niagara systems, user parameters, data interfaces and data channels

Related skills

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