Add runtime spline creation and editing (WIP)

Spline placement: New Spline button (S key) enters placement mode where clicks
add control points. Right-click/Enter finishes, Escape cancels. Min 2 points.
Spline visualization as cross-shaped quad strip (vertical + horizontal ribbons).

Point editing: select spline to show handles, click a handle to position gizmo
on it, then use translate gizmo to move individual points. Undo supported via
full-state snapshots (SplinePointAction).

Visual feedback: auto-generated M_PS_Editor_SplineLine material (unlit opaque
with depth test) for normal state. Gizmo material (no depth test) for selected
state. Center cube at centroid for whole-spline selection. Handles highlight
on selection.

Serialization: spline points exported to CustomProperties (PointCount + Point_N).
C++ class fallback via FindObject for LoadScene. Spline appears in scene outliner.

Still WIP: depth material swap on selection, serialization edge cases, and
point editing polish to be refined.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Unreal/Plugins/PS_Editor/Source/PS_Editor/GameMode/PS_Editor_Pawn.cpp

@@ -13,6 +13,7 @@
 #include "PS_Editor_PlayerController.h"
 #include "PS_Editor_Gizmo.h"
 #include "PS_Editor_UndoManager.h"
+#include "PS_Editor_SplineActor.h"
 #include "DrawDebugHelpers.h"
 #include "PS_Editor_ConfirmDialog.h"
 
@@ -199,6 +200,19 @@ void APS_Editor_Pawn::CreateInputActions()
 	IA_Paste = NewObject<UInputAction>(this, TEXT("IA_Paste"));
 	IA_Paste->ValueType = EInputActionValueType::Boolean;
 	EditorMappingContext->MapKey(IA_Paste, EKeys::V);
+
+	// Spline mode / Confirm / Cancel
+	IA_SplineMode = NewObject<UInputAction>(this, TEXT("IA_SplineMode"));
+	IA_SplineMode->ValueType = EInputActionValueType::Boolean;
+	EditorMappingContext->MapKey(IA_SplineMode, EKeys::S);
+
+	IA_Confirm = NewObject<UInputAction>(this, TEXT("IA_Confirm"));
+	IA_Confirm->ValueType = EInputActionValueType::Boolean;
+	EditorMappingContext->MapKey(IA_Confirm, EKeys::Enter);
+
+	IA_Cancel = NewObject<UInputAction>(this, TEXT("IA_Cancel"));
+	IA_Cancel->ValueType = EInputActionValueType::Boolean;
+	EditorMappingContext->MapKey(IA_Cancel, EKeys::Escape);
 }
 
 void APS_Editor_Pawn::SetupPlayerInputComponent(UInputComponent* PlayerInputComponent)
@@ -242,6 +256,9 @@ void APS_Editor_Pawn::SetupPlayerInputComponent(UInputComponent* PlayerInputComp
 	EIC->BindAction(IA_Duplicate, ETriggerEvent::Started, this, &APS_Editor_Pawn::HandleDuplicate);
 	EIC->BindAction(IA_Copy, ETriggerEvent::Started, this, &APS_Editor_Pawn::HandleCopy);
 	EIC->BindAction(IA_Paste, ETriggerEvent::Started, this, &APS_Editor_Pawn::HandlePaste);
+	EIC->BindAction(IA_SplineMode, ETriggerEvent::Started, this, &APS_Editor_Pawn::HandleSplineMode);
+	EIC->BindAction(IA_Confirm, ETriggerEvent::Started, this, &APS_Editor_Pawn::HandleConfirm);
+	EIC->BindAction(IA_Cancel, ETriggerEvent::Started, this, &APS_Editor_Pawn::HandleCancel);
 }
 
 // ---- Input Handlers ----
@@ -357,11 +374,26 @@ void APS_Editor_Pawn::HandleLook(const FInputActionValue& Value)
 			}
 			const FVector ConstrainedDelta = DisplacementAlongAxis * AxisDir;
 
-			for (int32 i = 0; i < Selected.Num() && i < GizmoDragInitialTransforms.Num(); ++i)
+			// Spline point mode: move the single point instead of actors
+			if (ActiveSplinePointIndex >= 0 && DraggedSplineActor.IsValid())
 			{
-				if (AActor* Actor = Selected[i].Get())
+				if (APS_Editor_SplineActor* SplineActor = Cast<APS_Editor_SplineActor>(DraggedSplineActor.Get()))
 				{
-					Actor->SetActorLocation(GizmoDragInitialTransforms[i].GetLocation() + ConstrainedDelta);
+					if (SplinePointDragInitialState.IsValidIndex(ActiveSplinePointIndex))
+					{
+						const FVector NewPos = SplinePointDragInitialState[ActiveSplinePointIndex] + ConstrainedDelta;
+						SplineActor->MovePoint(ActiveSplinePointIndex, NewPos);
+					}
+				}
+			}
+			else
+			{
+				for (int32 i = 0; i < Selected.Num() && i < GizmoDragInitialTransforms.Num(); ++i)
+				{
+					if (AActor* Actor = Selected[i].Get())
+					{
+						Actor->SetActorLocation(GizmoDragInitialTransforms[i].GetLocation() + ConstrainedDelta);
+					}
 				}
 			}
 		}
@@ -432,10 +464,33 @@ void APS_Editor_Pawn::HandleLook(const FInputActionValue& Value)
 			}
 		}
 
-		// In translate mode, gizmo follows the selection. In rotate/scale, stay at initial position.
+		// In translate mode, gizmo follows the target
 		if (Mode == EPS_Editor_TransformMode::Translate)
 		{
-			Gizmo->SetActorLocation(SM->GetSelectionPivot());
+			if (ActiveSplinePointIndex >= 0 && DraggedSplineActor.IsValid())
+			{
+				// Following a single spline point
+				if (APS_Editor_SplineActor* SplineActor = Cast<APS_Editor_SplineActor>(DraggedSplineActor.Get()))
+				{
+					Gizmo->SetActorLocation(SplineActor->GetPointLocation(ActiveSplinePointIndex));
+				}
+			}
+			else if (Selected.Num() == 1)
+			{
+				// Single actor: use centroid for splines, location for others
+				if (APS_Editor_SplineActor* SplineActor = Cast<APS_Editor_SplineActor>(Selected[0].Get()))
+				{
+					Gizmo->SetActorLocation(SplineActor->GetCentroid());
+				}
+				else
+				{
+					Gizmo->SetActorLocation(SM->GetSelectionPivot());
+				}
+			}
+			else
+			{
+				Gizmo->SetActorLocation(SM->GetSelectionPivot());
+			}
 		}
 
 		// Update local orientation in real-time during rotation drag
@@ -447,6 +502,25 @@ void APS_Editor_Pawn::HandleLook(const FInputActionValue& Value)
 			}
 		}
 	}
+	else if (CameraMode == EPS_Editor_CameraMode::SplinePointDrag)
+	{
+		// Drag spline point along horizontal plane
+		APS_Editor_SplineActor* Spline = Cast<APS_Editor_SplineActor>(DraggedSplineActor.Get());
+		if (!Spline || ActiveSplinePointIndex < 0) return;
+
+		FVector RayOrigin, RayDir;
+		if (!GetMouseWorldRay(RayOrigin, RayDir)) return;
+
+		// Ray-plane intersection
+		const float Denom = FVector::DotProduct(RayDir, SplinePointDragPlaneNormal);
+		if (FMath::Abs(Denom) < KINDA_SMALL_NUMBER) return;
+
+		const float T = FVector::DotProduct(SplinePointDragPlaneOrigin - RayOrigin, SplinePointDragPlaneNormal) / Denom;
+		if (T < 0.0f) return;
+
+		const FVector NewPos = RayOrigin + RayDir * T;
+		Spline->MovePoint(ActiveSplinePointIndex, NewPos);
+	}
 }
 
 void APS_Editor_Pawn::HandleScroll(const FInputActionValue& Value)
@@ -502,6 +576,60 @@ void APS_Editor_Pawn::HandleLeftClickStarted(const FInputActionValue& Value)
 		}
 	}
 
+	// Check for spline point handle hit → select point, move gizmo to it (no drag yet)
+	if (APS_Editor_PlayerController* EdPC = Cast<APS_Editor_PlayerController>(GetController()))
+	{
+		if (EdPC->GetEditorMode() == EPS_Editor_EditorMode::Normal)
+		{
+			if (UPS_Editor_SelectionManager* SM = EdPC->GetSelectionManager())
+			{
+				for (const TWeakObjectPtr<AActor>& Weak : SM->GetSelectedActors())
+				{
+					if (APS_Editor_SplineActor* Spline = Cast<APS_Editor_SplineActor>(Weak.Get()))
+					{
+						// First check: did we hit the center cube? If so, skip handle detection
+						// (let the click fall through to normal selection → gizmo at actor pivot)
+						FHitResult SplineHit;
+						FCollisionQueryParams SplineParams;
+						SplineParams.AddIgnoredActor(this);
+						const FVector TraceEnd = RayOrigin + RayDir * 100000.0f;
+						if (GetWorld()->LineTraceSingleByChannel(SplineHit, RayOrigin, TraceEnd, ECC_Visibility, SplineParams))
+						{
+							if (Spline->IsCenterCube(SplineHit.GetComponent()))
+							{
+								// Center cube hit → reset point selection, let normal flow handle it
+								ActiveSplinePointIndex = -1;
+								DraggedSplineActor = nullptr;
+								Spline->ClearHandleHighlight();
+								break;
+							}
+						}
+
+						const int32 HandleIdx = Spline->GetHandleIndexUnderCursor(RayOrigin, RayDir);
+						if (HandleIdx >= 0)
+						{
+							ActiveSplinePointIndex = HandleIdx;
+							DraggedSplineActor = Spline;
+							Spline->HighlightHandle(HandleIdx);
+
+							if (APS_Editor_Gizmo* Gizmo = SM->GetGizmo())
+							{
+								Gizmo->SetActorLocation(Spline->GetPointLocation(HandleIdx));
+							}
+
+							SM->SetTransformMode(EPS_Editor_TransformMode::Translate);
+							return;
+						}
+					}
+				}
+			}
+		}
+	}
+
+	// Clicking elsewhere resets spline point selection
+	ActiveSplinePointIndex = -1;
+	DraggedSplineActor = nullptr;
+
 	// No gizmo hit: enter PendingClick
 	PendingClickScreenPos = GetMouseScreenPosition();
 	SetCameraMode(EPS_Editor_CameraMode::PendingClick);
@@ -522,8 +650,22 @@ void APS_Editor_Pawn::HandleLeftClickCompleted(const FInputActionValue& Value)
 		{
 			if (UPS_Editor_UndoManager* UM = EditorPC->GetUndoManager())
 			{
-				if (UPS_Editor_SelectionManager* SM = EditorPC->GetSelectionManager())
+				// Spline point drag: record SplinePointAction
+				if (ActiveSplinePointIndex >= 0 && DraggedSplineActor.IsValid())
 				{
+					if (APS_Editor_SplineActor* SplineActor = Cast<APS_Editor_SplineActor>(DraggedSplineActor.Get()))
+					{
+						TSharedPtr<FPS_Editor_SplinePointAction> Action = MakeShared<FPS_Editor_SplinePointAction>();
+						Action->SplineActor = SplineActor;
+						Action->OldPoints = SplinePointDragInitialState;
+						Action->NewPoints = SplineActor->GetAllPointLocations();
+						Action->Description = TEXT("Move spline point");
+						UM->RecordAction(Action);
+					}
+				}
+				else if (UPS_Editor_SelectionManager* SM = EditorPC->GetSelectionManager())
+				{
+					// Normal: record TransformAction
 					TSharedPtr<FPS_Editor_TransformAction> Action = MakeShared<FPS_Editor_TransformAction>();
 					const TArray<TWeakObjectPtr<AActor>>& Selected = SM->GetSelectedActors();
 
@@ -555,17 +697,53 @@ void APS_Editor_Pawn::HandleLeftClickCompleted(const FInputActionValue& Value)
 		}
 		ActiveGizmoAxis = EPS_Editor_GizmoAxis::None;
 
-		// Refresh gizmo orientation (local mode needs to track actor's new rotation)
+		// Refresh gizmo: keep at spline point if editing, else refresh orientation
 		if (APS_Editor_PlayerController* PC2 = Cast<APS_Editor_PlayerController>(GetController()))
 		{
 			if (UPS_Editor_SelectionManager* SM2 = PC2->GetSelectionManager())
 			{
-				SM2->RefreshGizmoOrientation();
+				if (ActiveSplinePointIndex >= 0 && DraggedSplineActor.IsValid())
+				{
+					// Keep gizmo at the active spline point
+					if (APS_Editor_SplineActor* SplineActor = Cast<APS_Editor_SplineActor>(DraggedSplineActor.Get()))
+					{
+						if (APS_Editor_Gizmo* G = SM2->GetGizmo())
+						{
+							G->SetActorLocation(SplineActor->GetPointLocation(ActiveSplinePointIndex));
+						}
+					}
+				}
+				else
+				{
+					SM2->RefreshGizmoOrientation();
+				}
 			}
 		}
 
 		SetCameraMode(EPS_Editor_CameraMode::Idle);
 	}
+	else if (CameraMode == EPS_Editor_CameraMode::SplinePointDrag)
+	{
+		// Record undo for spline point move
+		if (APS_Editor_SplineActor* Spline = Cast<APS_Editor_SplineActor>(DraggedSplineActor.Get()))
+		{
+			if (APS_Editor_PlayerController* EditorPC = Cast<APS_Editor_PlayerController>(GetController()))
+			{
+				if (UPS_Editor_UndoManager* UM = EditorPC->GetUndoManager())
+				{
+					TSharedPtr<FPS_Editor_SplinePointAction> Action = MakeShared<FPS_Editor_SplinePointAction>();
+					Action->SplineActor = Spline;
+					Action->OldPoints = SplinePointDragInitialState;
+					Action->NewPoints = Spline->GetAllPointLocations();
+					Action->Description = TEXT("Move spline point");
+					UM->RecordAction(Action);
+				}
+			}
+		}
+		ActiveSplinePointIndex = -1;
+		DraggedSplineActor = nullptr;
+		SetCameraMode(EPS_Editor_CameraMode::Idle);
+	}
 	else if (CameraMode == EPS_Editor_CameraMode::Pan || CameraMode == EPS_Editor_CameraMode::Orbit)
 	{
 		SetCameraMode(EPS_Editor_CameraMode::Idle);
@@ -574,6 +752,15 @@ void APS_Editor_Pawn::HandleLeftClickCompleted(const FInputActionValue& Value)
 
 void APS_Editor_Pawn::HandleRightClickStarted(const FInputActionValue& Value)
 {
+	// In spline placement mode, right-click finishes the spline
+	if (APS_Editor_PlayerController* EditorPC = Cast<APS_Editor_PlayerController>(GetController()))
+	{
+		if (EditorPC->GetEditorMode() == EPS_Editor_EditorMode::SplinePlacement)
+		{
+			EditorPC->FinishSplinePlacement();
+			return;
+		}
+	}
 	SetCameraMode(EPS_Editor_CameraMode::Fly);
 }
 
@@ -760,6 +947,44 @@ void APS_Editor_Pawn::HandlePaste(const FInputActionValue& Value)
 	}
 }
 
+void APS_Editor_Pawn::HandleSplineMode(const FInputActionValue& Value)
+{
+	if (CameraMode != EPS_Editor_CameraMode::Idle) return;
+	if (APS_Editor_PlayerController* EditorPC = Cast<APS_Editor_PlayerController>(GetController()))
+	{
+		if (EditorPC->GetEditorMode() == EPS_Editor_EditorMode::SplinePlacement)
+		{
+			EditorPC->FinishSplinePlacement();
+		}
+		else
+		{
+			EditorPC->BeginSplinePlacement();
+		}
+	}
+}
+
+void APS_Editor_Pawn::HandleConfirm(const FInputActionValue& Value)
+{
+	if (APS_Editor_PlayerController* EditorPC = Cast<APS_Editor_PlayerController>(GetController()))
+	{
+		if (EditorPC->GetEditorMode() == EPS_Editor_EditorMode::SplinePlacement)
+		{
+			EditorPC->FinishSplinePlacement();
+		}
+	}
+}
+
+void APS_Editor_Pawn::HandleCancel(const FInputActionValue& Value)
+{
+	if (APS_Editor_PlayerController* EditorPC = Cast<APS_Editor_PlayerController>(GetController()))
+	{
+		if (EditorPC->GetEditorMode() == EPS_Editor_EditorMode::SplinePlacement)
+		{
+			EditorPC->CancelSplinePlacement();
+		}
+	}
+}
+
 // ---- Helpers ----
 
 void APS_Editor_Pawn::SetCameraMode(EPS_Editor_CameraMode NewMode)
@@ -944,5 +1169,14 @@ void APS_Editor_Pawn::BeginGizmoDrag(EPS_Editor_GizmoAxis Axis)
 		}
 	}
 
+	// Store initial spline state if editing a point
+	if (ActiveSplinePointIndex >= 0 && DraggedSplineActor.IsValid())
+	{
+		if (APS_Editor_SplineActor* Spline = Cast<APS_Editor_SplineActor>(DraggedSplineActor.Get()))
+		{
+			SplinePointDragInitialState = Spline->GetAllPointLocations();
+		}
+	}
+
 	SetCameraMode(EPS_Editor_CameraMode::GizmoDrag);
 }

Unreal/Plugins/PS_Editor/Source/PS_Editor/GameMode/PS_Editor_Pawn.h

@@ -31,7 +31,9 @@ enum class EPS_Editor_CameraMode : uint8
 	/** Alt + left-click or middle-click: orbit around focal point. */
 	Orbit,
 	/** Dragging a gizmo handle. */
-	GizmoDrag
+	GizmoDrag,
+	/** Dragging a spline point handle. */
+	SplinePointDrag
 };
 
 /**
@@ -180,6 +182,22 @@ private:
 	UPROPERTY()
 	TObjectPtr<UInputAction> IA_Paste;
 
+	UPROPERTY()
+	TObjectPtr<UInputAction> IA_SplineMode;
+
+	UPROPERTY()
+	TObjectPtr<UInputAction> IA_Confirm;
+
+	UPROPERTY()
+	TObjectPtr<UInputAction> IA_Cancel;
+
+	// ---- Spline point drag state ----
+	int32 ActiveSplinePointIndex = -1;
+	TWeakObjectPtr<AActor> DraggedSplineActor;
+	TArray<FVector> SplinePointDragInitialState;
+	FVector SplinePointDragPlaneOrigin;
+	FVector SplinePointDragPlaneNormal;
+
 	// ---- Modifier key state ----
 	bool bAltHeld = false;
 	bool bCtrlHeld = false;
@@ -216,6 +234,9 @@ private:
 	void HandleDuplicate(const FInputActionValue& Value);
 	void HandleCopy(const FInputActionValue& Value);
 	void HandlePaste(const FInputActionValue& Value);
+	void HandleSplineMode(const FInputActionValue& Value);
+	void HandleConfirm(const FInputActionValue& Value);
+	void HandleCancel(const FInputActionValue& Value);
 
 	// ---- Helpers ----
 	void CreateInputActions();

Unreal/Plugins/PS_Editor/Source/PS_Editor/GameMode/PS_Editor_PlayerController.cpp

@@ -5,6 +5,7 @@
 #include "PS_Editor_SceneSerializer.h"
 #include "PS_Editor_Gizmo.h"
 #include "PS_Editor_Pawn.h"
+#include "PS_Editor_SplineActor.h"
 
 APS_Editor_PlayerController::APS_Editor_PlayerController()
 {
@@ -80,8 +81,116 @@ void APS_Editor_PlayerController::OnPossess(APawn* InPawn)
 	}
 }
 
+void APS_Editor_PlayerController::BeginSplinePlacement()
+{
+	if (SelectionManager)
+	{
+		SelectionManager->ClearSelection();
+	}
+	ActiveSplineActor = nullptr;
+	EditorMode = EPS_Editor_EditorMode::SplinePlacement;
+	UE_LOG(LogTemp, Log, TEXT("PS_Editor: Spline placement mode started"));
+}
+
+void APS_Editor_PlayerController::FinishSplinePlacement()
+{
+	if (!ActiveSplineActor || ActiveSplineActor->GetNumPoints() < 2)
+	{
+		CancelSplinePlacement();
+		return;
+	}
+
+	// Hide handles after placement (shown again on selection)
+	ActiveSplineActor->SetHandlesVisible(false);
+
+	// Track in SpawnManager — CRITICAL for outliner, save/load, and scene clear
+	if (SpawnManager)
+	{
+		SpawnManager->TrackSpawnedActor(ActiveSplineActor);
+		UE_LOG(LogTemp, Log, TEXT("PS_Editor: Spline tracked by SpawnManager (total: %d)"), SpawnManager->GetSpawnedActors().Num());
+	}
+	else
+	{
+		UE_LOG(LogTemp, Error, TEXT("PS_Editor: SpawnManager is null! Spline will NOT be tracked."));
+	}
+
+	// Record spawn action for undo
+	if (UndoManager)
+	{
+		TSharedPtr<FPS_Editor_SpawnAction> Action = MakeShared<FPS_Editor_SpawnAction>();
+		Action->Actors.Add(ActiveSplineActor);
+		Action->Description = FString::Printf(TEXT("Create spline (%d points)"), ActiveSplineActor->GetNumPoints());
+		UndoManager->RecordAction(Action);
+	}
+
+	// Select the new spline
+	if (SelectionManager)
+	{
+		SelectionManager->SelectActor(ActiveSplineActor);
+	}
+
+	UE_LOG(LogTemp, Log, TEXT("PS_Editor: Spline placed with %d points, class=%s"),
+		ActiveSplineActor->GetNumPoints(), *ActiveSplineActor->GetClass()->GetPathName());
+
+	ActiveSplineActor = nullptr;
+	EditorMode = EPS_Editor_EditorMode::Normal;
+}
+
+void APS_Editor_PlayerController::CancelSplinePlacement()
+{
+	if (ActiveSplineActor)
+	{
+		ActiveSplineActor->Destroy();
+		ActiveSplineActor = nullptr;
+	}
+	EditorMode = EPS_Editor_EditorMode::Normal;
+	UE_LOG(LogTemp, Log, TEXT("PS_Editor: Spline placement cancelled"));
+}
+
 void APS_Editor_PlayerController::HandleEditorClick(FVector2D ScreenPos, bool bAdditive)
 {
+	if (EditorMode == EPS_Editor_EditorMode::SplinePlacement)
+	{
+		// Deproject click to world position
+		FVector WorldOrigin, WorldDirection;
+		if (!DeprojectScreenPositionToWorld(ScreenPos.X, ScreenPos.Y, WorldOrigin, WorldDirection))
+			return;
+
+		FHitResult Hit;
+		FCollisionQueryParams Params;
+		Params.AddIgnoredActor(GetPawn());
+		if (ActiveSplineActor) Params.AddIgnoredActor(ActiveSplineActor);
+
+		const FVector End = WorldOrigin + WorldDirection * 100000.0f;
+		FVector ClickWorldPos;
+		if (GetWorld()->LineTraceSingleByChannel(Hit, WorldOrigin, End, ECC_Visibility, Params))
+		{
+			ClickWorldPos = Hit.ImpactPoint;
+		}
+		else
+		{
+			ClickWorldPos = WorldOrigin + WorldDirection * 1000.0f;
+		}
+
+		if (!ActiveSplineActor)
+		{
+			// First click: spawn the spline actor
+			FActorSpawnParameters SpawnParams;
+			SpawnParams.SpawnCollisionHandlingOverride = ESpawnActorCollisionHandlingMethod::AlwaysSpawn;
+			ActiveSplineActor = GetWorld()->SpawnActor<APS_Editor_SplineActor>(
+				APS_Editor_SplineActor::StaticClass(), ClickWorldPos, FRotator::ZeroRotator, SpawnParams);
+		}
+
+		if (ActiveSplineActor)
+		{
+			ActiveSplineActor->AddPoint(ClickWorldPos);
+			UE_LOG(LogTemp, Log, TEXT("PS_Editor: Spline point %d added at %s"),
+				ActiveSplineActor->GetNumPoints(), *ClickWorldPos.ToString());
+		}
+		return;
+	}
+
+	// Normal mode: selection
 	if (SelectionManager)
 	{
 		SelectionManager->HandleClickAtScreenPosition(ScreenPos, bAdditive);

Unreal/Plugins/PS_Editor/Source/PS_Editor/GameMode/PS_Editor_PlayerController.h

@@ -2,6 +2,7 @@
 
 #include "CoreMinimal.h"
 #include "GameFramework/PlayerController.h"
+#include "PS_Editor_SelectionTypes.h"
 #include "PS_Editor_PlayerController.generated.h"
 
 class UPS_Editor_SelectionManager;
@@ -9,6 +10,7 @@ class UPS_Editor_UndoManager;
 class UPS_Editor_SpawnManager;
 class UPS_Editor_SpawnCatalog;
 class UPS_Editor_SceneSerializer;
+class APS_Editor_SplineActor;
 
 /**
  * Player controller for PS_Editor runtime editing.
@@ -38,6 +40,23 @@ public:
 	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "PS Editor")
 	TSoftObjectPtr<UPS_Editor_SpawnCatalog> SpawnCatalogAsset;
 
+	// ---- Editor Mode (Normal / SplinePlacement) ----
+
+	UFUNCTION(BlueprintCallable, Category = "PS Editor")
+	EPS_Editor_EditorMode GetEditorMode() const { return EditorMode; }
+
+	/** Enter spline placement mode. Clicks will add points. */
+	void BeginSplinePlacement();
+
+	/** Finish current spline (min 2 points required). Returns to Normal mode. */
+	void FinishSplinePlacement();
+
+	/** Cancel current spline placement (destroys in-progress spline). */
+	void CancelSplinePlacement();
+
+	/** Get the spline currently being placed (nullptr if not in SplinePlacement mode). */
+	APS_Editor_SplineActor* GetActiveSplineActor() const { return ActiveSplineActor; }
+
 protected:
 	virtual void BeginPlay() override;
 	virtual void OnPossess(APawn* InPawn) override;
@@ -55,5 +74,10 @@ private:
 	UPROPERTY()
 	TObjectPtr<UPS_Editor_SceneSerializer> SceneSerializer;
 
+	EPS_Editor_EditorMode EditorMode = EPS_Editor_EditorMode::Normal;
+
+	UPROPERTY()
+	TObjectPtr<APS_Editor_SplineActor> ActiveSplineActor;
+
 	void HandleEditorClick(FVector2D ScreenPos, bool bAdditive);
 };

Unreal/Plugins/PS_Editor/Source/PS_Editor/PS_Editor.Build.cs

@@ -17,6 +17,7 @@ public class PS_Editor : ModuleRules
 		PublicIncludePaths.Add(Path.Combine(SourceDir, "Gizmo"));
 		PublicIncludePaths.Add(Path.Combine(SourceDir, "Spawn"));
 		PublicIncludePaths.Add(Path.Combine(SourceDir, "Serialization"));
+		PublicIncludePaths.Add(Path.Combine(SourceDir, "Spline"));
 
 		PublicDependencyModuleNames.AddRange(new string[]
 		{

Unreal/Plugins/PS_Editor/Source/PS_Editor/PS_Editor.cpp

@@ -15,6 +15,7 @@
 #include "Materials/MaterialExpressionLinearInterpolate.h"
 #include "Materials/MaterialExpressionComponentMask.h"
 #include "Materials/MaterialExpressionAppendVector.h"
+#include "Materials/MaterialExpressionVectorParameter.h"
 #include "AssetRegistry/AssetRegistryModule.h"
 #include "UObject/SavePackage.h"
 #include "Misc/PackageName.h"
@@ -218,6 +219,48 @@ static void CreateOutlineMaterialAsset()
 
 	UE_LOG(LogTemp, Log, TEXT("PS_Editor: Selection outline material auto-generated (8-sample, dynamic resolution)"));
 }
+
+static void CreateSplineLineMaterialAsset()
+{
+	const FString MaterialPath = TEXT("/PS_Editor/M_PS_Editor_SplineLine");
+	const FString AssetName = TEXT("M_PS_Editor_SplineLine");
+
+	if (LoadObject<UMaterial>(nullptr, *(MaterialPath + TEXT(".") + AssetName)))
+	{
+		return; // Already exists
+	}
+
+	UPackage* Package = CreatePackage(*MaterialPath);
+	UMaterial* Mat = NewObject<UMaterial>(Package, *AssetName, RF_Public | RF_Standalone);
+	Mat->MaterialDomain = EMaterialDomain::MD_Surface;
+	Mat->SetShadingModel(EMaterialShadingModel::MSM_Unlit);
+	Mat->BlendMode = EBlendMode::BLEND_Opaque;
+	Mat->TwoSided = true;
+
+	auto AddExpr = [&](UMaterialExpression* Expr) { Mat->GetExpressionCollection().AddExpression(Expr); };
+
+	// Vector parameter "Color" (default orange)
+	UMaterialExpressionVectorParameter* ColorParam = NewObject<UMaterialExpressionVectorParameter>(Mat);
+	ColorParam->ParameterName = TEXT("Color");
+	ColorParam->DefaultValue = FLinearColor(1.0f, 0.4f, 0.0f, 1.0f);
+	AddExpr(ColorParam);
+	ColorParam->MaterialExpressionEditorX = -200;
+	ColorParam->MaterialExpressionEditorY = 0;
+
+	// Connect Color → Emissive
+	Mat->GetEditorOnlyData()->EmissiveColor.Connect(0, ColorParam);
+
+	Mat->PreEditChange(nullptr);
+	Mat->PostEditChange();
+
+	FString PackageFilename = FPackageName::LongPackageNameToFilename(MaterialPath, FPackageName::GetAssetPackageExtension());
+	FSavePackageArgs SaveArgs;
+	SaveArgs.TopLevelFlags = RF_Public | RF_Standalone;
+	UPackage::SavePackage(Package, Mat, *PackageFilename, SaveArgs);
+	FAssetRegistryModule::AssetCreated(Mat);
+
+	UE_LOG(LogTemp, Log, TEXT("PS_Editor: Spline line material auto-generated (unlit opaque with Color parameter)"));
+}
 #endif
 
 void FPS_EditorModule::StartupModule()
@@ -226,6 +269,7 @@ void FPS_EditorModule::StartupModule()
 
 #if WITH_EDITOR
 	FCoreDelegates::OnPostEngineInit.AddStatic(&CreateOutlineMaterialAsset);
+	FCoreDelegates::OnPostEngineInit.AddStatic(&CreateSplineLineMaterialAsset);
 #endif
 }
 

Unreal/Plugins/PS_Editor/Source/PS_Editor/Selection/PS_Editor_SelectionManager.cpp

@@ -4,6 +4,7 @@
 #include "PS_Editor_PlayerController.h"
 #include "PS_Editor_SpawnManager.h"
 #include "PS_Editor_EditableComponent.h"
+#include "PS_Editor_SplineActor.h"
 #include "GameFramework/PlayerController.h"
 #include "Engine/World.h"
 #include "GameFramework/Pawn.h"
@@ -185,6 +186,13 @@ void UPS_Editor_SelectionManager::SelectActor(AActor* Actor)
 	UpdateGizmo();
 	OnSelectionChanged.Broadcast();
 
+	// Show spline handles and mark selected
+	if (APS_Editor_SplineActor* Spline = Cast<APS_Editor_SplineActor>(Actor))
+	{
+		Spline->SetHandlesVisible(true);
+		Spline->SetSelected(true);
+	}
+
 	UE_LOG(LogTemp, Log, TEXT("PS_Editor: Selected %s"), *Actor->GetName());
 }
 
@@ -206,6 +214,13 @@ void UPS_Editor_SelectionManager::DeselectActor(AActor* Actor)
 		UpdateGizmo();
 		OnSelectionChanged.Broadcast();
 
+		// Hide spline handles and unmark
+		if (APS_Editor_SplineActor* Spline = Cast<APS_Editor_SplineActor>(Actor))
+		{
+			Spline->SetHandlesVisible(false);
+			Spline->SetSelected(false);
+		}
+
 		UE_LOG(LogTemp, Log, TEXT("PS_Editor: Deselected %s"), *Actor->GetName());
 	}
 }
@@ -269,7 +284,15 @@ FVector UPS_Editor_SelectionManager::GetSelectionPivot() const
 	{
 		if (AActor* Actor = Weak.Get())
 		{
-			Sum += Actor->GetActorLocation();
+			// For SplineActors, use the centroid of all points as pivot
+			if (APS_Editor_SplineActor* Spline = Cast<APS_Editor_SplineActor>(Actor))
+			{
+				Sum += Spline->GetCentroid();
+			}
+			else
+			{
+				Sum += Actor->GetActorLocation();
+			}
 			Count++;
 		}
 	}
@@ -448,7 +471,18 @@ void UPS_Editor_SelectionManager::UpdateGizmo()
 
 	if (IsAnythingSelected())
 	{
-		Gizmo->SetGizmoActive(true, GetSelectionPivot());
+		FVector Pivot = GetSelectionPivot();
+
+		// Override pivot for SplineActors: use centroid so gizmo aligns with center cube
+		if (SelectedActors.Num() == 1)
+		{
+			if (APS_Editor_SplineActor* Spline = Cast<APS_Editor_SplineActor>(SelectedActors[0].Get()))
+			{
+				Pivot = Spline->GetCentroid();
+			}
+		}
+
+		Gizmo->SetGizmoActive(true, Pivot);
 
 		// Update gizmo orientation
 		if (AActor* Actor = SelectedActors[0].Get())

Unreal/Plugins/PS_Editor/Source/PS_Editor/Selection/PS_Editor_SelectionTypes.h

@@ -33,3 +33,11 @@ enum class EPS_Editor_Space : uint8
 	World,
 	Local
 };
+
+/** Top-level editor mode (separate from transform mode). */
+UENUM(BlueprintType)
+enum class EPS_Editor_EditorMode : uint8
+{
+	Normal,           // Standard select/transform behavior
+	SplinePlacement   // Clicks add points to current spline
+};

Unreal/Plugins/PS_Editor/Source/PS_Editor/Selection/PS_Editor_UndoManager.cpp

@@ -1,7 +1,24 @@
 #include "PS_Editor_UndoManager.h"
+#include "PS_Editor_SplineActor.h"
 #include "UObject/UnrealType.h"
 #include "Components/ActorComponent.h"
 
+void FPS_Editor_SplinePointAction::Execute()
+{
+	if (APS_Editor_SplineActor* Spline = SplineActor.Get())
+	{
+		Spline->SetAllPointLocations(NewPoints);
+	}
+}
+
+void FPS_Editor_SplinePointAction::Undo()
+{
+	if (APS_Editor_SplineActor* Spline = SplineActor.Get())
+	{
+		Spline->SetAllPointLocations(OldPoints);
+	}
+}
+
 void FPS_Editor_PropertyAction::ApplyValue(const FString& ValueStr)
 {
 	AActor* Act = Actor.Get();

Unreal/Plugins/PS_Editor/Source/PS_Editor/Selection/PS_Editor_UndoManager.h

@@ -9,7 +9,8 @@ enum class EPS_Editor_ActionType : uint8
 	Transform,
 	Delete,
 	Spawn,
-	PropertyChange
+	PropertyChange,
+	SplinePointChange
 };
 
 /**
@@ -157,6 +158,26 @@ struct FPS_Editor_SpawnAction : public FPS_Editor_Action
 	}
 };
 
+class APS_Editor_SplineActor;
+
+/**
+ * Records a spline point state change (move, add, remove).
+ * Stores full state snapshots (all points before/after) for simplicity.
+ */
+struct FPS_Editor_SplinePointAction : public FPS_Editor_Action
+{
+	FPS_Editor_SplinePointAction() : FPS_Editor_Action(EPS_Editor_ActionType::SplinePointChange) {}
+
+	TWeakObjectPtr<APS_Editor_SplineActor> SplineActor;
+	TArray<FVector> OldPoints;
+	TArray<FVector> NewPoints;
+	FString Description;
+
+	virtual void Execute() override;
+	virtual void Undo() override;
+	virtual FString GetDescription() const override { return Description; }
+};
+
 /**
  * Records a single property value change on a component or actor.
  * Stores text-serialized old/new values for undo/redo via ImportText.

Unreal/Plugins/PS_Editor/Source/PS_Editor/Serialization/PS_Editor_SceneSerializer.cpp

@@ -2,6 +2,7 @@
 #include "PS_Editor_SpawnManager.h"
 #include "PS_Editor_SelectionManager.h"
 #include "PS_Editor_EditableComponent.h"
+#include "PS_Editor_SplineActor.h"
 #include "JsonObjectConverter.h"
 #include "Misc/FileHelper.h"
 #include "Misc/Paths.h"
@@ -36,6 +37,14 @@ bool UPS_Editor_SceneSerializer::SaveScene(const FString& SceneName, UPS_Editor_
 		ActorData.Rotation = Actor->GetActorRotation();
 		ActorData.Scale = Actor->GetActorScale3D();
 
+		// Export spline data
+		if (APS_Editor_SplineActor* Spline = Cast<APS_Editor_SplineActor>(Actor))
+		{
+			Spline->ExportToCustomProperties(ActorData.CustomProperties);
+			UE_LOG(LogTemp, Log, TEXT("PS_Editor: Exported spline with %d points, class=%s"),
+				Spline->GetNumPoints(), *ActorData.ClassPath);
+		}
+
 		// Export custom editable properties
 		if (UPS_Editor_EditableComponent* EditComp = Actor->FindComponentByClass<UPS_Editor_EditableComponent>())
 		{
@@ -137,6 +146,11 @@ bool UPS_Editor_SceneSerializer::LoadScene(const FString& SceneName, UPS_Editor_
 	{
 		UClass* LoadedClass = LoadObject<UClass>(nullptr, *ActorData.ClassPath);
 		if (!LoadedClass)
+		{
+			// Fallback for C++ native classes (e.g. /Script/PS_Editor.PS_Editor_SplineActor)
+			LoadedClass = FindObject<UClass>(nullptr, *ActorData.ClassPath);
+		}
+		if (!LoadedClass)
 		{
 			UE_LOG(LogTemp, Warning, TEXT("PS_Editor: Failed to load class: %s"), *ActorData.ClassPath);
 			continue;
@@ -190,6 +204,12 @@ bool UPS_Editor_SceneSerializer::LoadScene(const FString& SceneName, UPS_Editor_
 				}
 			}
 
+			// Import spline data
+			if (APS_Editor_SplineActor* Spline = Cast<APS_Editor_SplineActor>(SpawnedActor))
+			{
+				Spline->ImportFromCustomProperties(ActorData.CustomProperties);
+			}
+
 			SpawnedCount++;
 		}
 	}

Unreal/Plugins/PS_Editor/Source/PS_Editor/Spline/PS_Editor_SplineActor.cpp

@@ -0,0 +1,493 @@
+#include "PS_Editor_SplineActor.h"
+#include "Components/SplineComponent.h"
+#include "ProceduralMeshComponent.h"
+#include "Components/StaticMeshComponent.h"
+#include "Engine/StaticMesh.h"
+#include "Materials/MaterialInstanceDynamic.h"
+
+APS_Editor_SplineActor::APS_Editor_SplineActor()
+{
+	PrimaryActorTick.bCanEverTick = false;
+
+	// Root
+	USceneComponent* Root = CreateDefaultSubobject<USceneComponent>(TEXT("Root"));
+	SetRootComponent(Root);
+	Root->SetMobility(EComponentMobility::Movable);
+
+	// Spline data
+	SplineComp = CreateDefaultSubobject<USplineComponent>(TEXT("SplineComp"));
+	SplineComp->SetupAttachment(Root);
+	SplineComp->ClearSplinePoints(false);
+	SplineComp->SetClosedLoop(false);
+
+	// Line mesh
+	SplineMeshComp = CreateDefaultSubobject<UProceduralMeshComponent>(TEXT("SplineMesh"));
+	SplineMeshComp->SetupAttachment(Root);
+	SplineMeshComp->SetCollisionEnabled(ECollisionEnabled::QueryOnly);
+	SplineMeshComp->SetCollisionResponseToAllChannels(ECR_Ignore);
+	SplineMeshComp->SetCollisionResponseToChannel(ECC_Visibility, ECR_Block);
+	SplineMeshComp->bUseComplexAsSimpleCollision = true;
+	SplineMeshComp->SetCastShadow(false);
+
+	// Handle parent
+	HandleRoot = CreateDefaultSubobject<USceneComponent>(TEXT("HandleRoot"));
+	HandleRoot->SetupAttachment(Root);
+}
+
+void APS_Editor_SplineActor::BeginPlay()
+{
+	Super::BeginPlay();
+
+	// Gizmo material (no depth test, renders on top) for handles and selected state
+	UMaterialInterface* GizmoMat = LoadObject<UMaterialInterface>(
+		nullptr, TEXT("/PS_Editor/M_PS_Editor_Gizmo.M_PS_Editor_Gizmo"));
+
+	// Auto-generated opaque unlit material (depth tested) for spline line
+	UMaterialInterface* SplineLineMat = LoadObject<UMaterialInterface>(
+		nullptr, TEXT("/PS_Editor/M_PS_Editor_SplineLine.M_PS_Editor_SplineLine"));
+
+	// Spline line: normal depth-tested material (orange)
+	if (SplineLineMat)
+	{
+		SplineMat = UMaterialInstanceDynamic::Create(SplineLineMat, this);
+		SplineMat->SetVectorParameterValue(TEXT("Color"), FLinearColor(1.0f, 0.4f, 0.0f));
+	}
+
+	// Spline line selected: no depth test (on top, bright orange)
+	if (GizmoMat)
+	{
+		SplineMatSelected = UMaterialInstanceDynamic::Create(GizmoMat, this);
+		SplineMatSelected->SetVectorParameterValue(TEXT("Color"), FLinearColor(1.0f, 0.6f, 0.0f));
+
+		// Handles always use gizmo material (on top, clickable)
+		HandleMat = UMaterialInstanceDynamic::Create(GizmoMat, this);
+		HandleMat->SetVectorParameterValue(TEXT("Color"), FLinearColor(1.0f, 1.0f, 1.0f)); // White
+
+		HandleHighlightMat = UMaterialInstanceDynamic::Create(GizmoMat, this);
+		HandleHighlightMat->SetVectorParameterValue(TEXT("Color"), FLinearColor(1.0f, 1.0f, 0.0f)); // Yellow
+
+		CenterCubeMat = UMaterialInstanceDynamic::Create(GizmoMat, this);
+		CenterCubeMat->SetVectorParameterValue(TEXT("Color"), FLinearColor(1.0f, 0.4f, 0.0f)); // Orange
+	}
+
+	// Create center cube (selection handle for whole spline)
+	CenterCube = NewObject<UStaticMeshComponent>(this);
+	CenterCube->SetupAttachment(GetRootComponent());
+	CenterCube->RegisterComponent();
+	UStaticMesh* CubeMesh = LoadObject<UStaticMesh>(nullptr, TEXT("/Engine/BasicShapes/Cube.Cube"));
+	if (CubeMesh)
+	{
+		CenterCube->SetStaticMesh(CubeMesh);
+	}
+	CenterCube->SetWorldScale3D(FVector(CenterCubeScale));
+	CenterCube->SetCollisionEnabled(ECollisionEnabled::QueryOnly);
+	CenterCube->SetCollisionResponseToAllChannels(ECR_Ignore);
+	CenterCube->SetCollisionResponseToChannel(ECC_Visibility, ECR_Block);
+	CenterCube->SetCastShadow(false);
+	if (CenterCubeMat)
+	{
+		CenterCube->SetMaterial(0, CenterCubeMat);
+	}
+}
+
+// ---- Point manipulation ----
+
+void APS_Editor_SplineActor::AddPoint(const FVector& WorldPosition)
+{
+	// Convert world to local space
+	const FVector LocalPos = GetActorTransform().InverseTransformPosition(WorldPosition);
+	SplineComp->AddSplinePoint(LocalPos, ESplineCoordinateSpace::Local, true);
+
+	// Create handle
+	UStaticMeshComponent* Handle = CreatePointHandle(WorldPosition);
+	PointHandles.Add(Handle);
+
+	UpdateVisualization();
+}
+
+void APS_Editor_SplineActor::MovePoint(int32 Index, const FVector& NewWorldPosition)
+{
+	if (Index < 0 || Index >= GetNumPoints()) return;
+
+	const FVector LocalPos = GetActorTransform().InverseTransformPosition(NewWorldPosition);
+	SplineComp->SetLocationAtSplinePoint(Index, LocalPos, ESplineCoordinateSpace::Local, true);
+
+	if (PointHandles.IsValidIndex(Index) && PointHandles[Index])
+	{
+		PointHandles[Index]->SetWorldLocation(NewWorldPosition);
+	}
+
+	UpdateVisualization();
+}
+
+void APS_Editor_SplineActor::RemovePoint(int32 Index)
+{
+	if (Index < 0 || Index >= GetNumPoints()) return;
+
+	SplineComp->RemoveSplinePoint(Index, true);
+
+	if (PointHandles.IsValidIndex(Index))
+	{
+		if (PointHandles[Index])
+		{
+			PointHandles[Index]->DestroyComponent();
+		}
+		PointHandles.RemoveAt(Index);
+	}
+
+	UpdateVisualization();
+}
+
+int32 APS_Editor_SplineActor::GetNumPoints() const
+{
+	return SplineComp ? SplineComp->GetNumberOfSplinePoints() : 0;
+}
+
+FVector APS_Editor_SplineActor::GetPointLocation(int32 Index) const
+{
+	if (!SplineComp || Index < 0 || Index >= GetNumPoints()) return FVector::ZeroVector;
+	return SplineComp->GetLocationAtSplinePoint(Index, ESplineCoordinateSpace::World);
+}
+
+TArray<FVector> APS_Editor_SplineActor::GetAllPointLocations() const
+{
+	TArray<FVector> Result;
+	const int32 Num = GetNumPoints();
+	Result.Reserve(Num);
+	for (int32 i = 0; i < Num; i++)
+	{
+		Result.Add(GetPointLocation(i));
+	}
+	return Result;
+}
+
+void APS_Editor_SplineActor::SetAllPointLocations(const TArray<FVector>& Points)
+{
+	if (!SplineComp) return;
+
+	SplineComp->ClearSplinePoints(false);
+	for (const FVector& WorldPos : Points)
+	{
+		const FVector LocalPos = GetActorTransform().InverseTransformPosition(WorldPos);
+		SplineComp->AddSplinePoint(LocalPos, ESplineCoordinateSpace::Local, false);
+	}
+	SplineComp->UpdateSpline();
+
+	RebuildHandles();
+	UpdateVisualization();
+}
+
+// ---- Visualization ----
+
+void APS_Editor_SplineActor::UpdateVisualization()
+{
+	if (!SplineMeshComp || !SplineComp || GetNumPoints() < 2)
+	{
+		if (SplineMeshComp) SplineMeshComp->ClearAllMeshSections();
+		return;
+	}
+
+	const float SplineLength = SplineComp->GetSplineLength();
+	const int32 NumSamples = FMath::Max(2, FMath::CeilToInt(SplineLength / SampleInterval));
+
+	TArray<FVector> Vertices;
+	TArray<int32> Triangles;
+	TArray<FVector> Normals;
+	TArray<FVector2D> UVs;
+
+	// 4 vertices per sample: 2 for vertical ribbon + 2 for horizontal ribbon (cross-section)
+	Vertices.Reserve(NumSamples * 4);
+	Normals.Reserve(NumSamples * 4);
+	UVs.Reserve(NumSamples * 4);
+
+	for (int32 i = 0; i < NumSamples; i++)
+	{
+		const float Distance = (static_cast<float>(i) / (NumSamples - 1)) * SplineLength;
+		const FVector Location = SplineComp->GetLocationAtDistanceAlongSpline(Distance, ESplineCoordinateSpace::Local);
+		const FVector Right = SplineComp->GetRightVectorAtDistanceAlongSpline(Distance, ESplineCoordinateSpace::Local);
+		const FVector Up = FVector(0.0f, 0.0f, LineHalfWidth);
+
+		const float U = static_cast<float>(i) / (NumSamples - 1);
+
+		// Vertical ribbon (visible from sides)
+		Vertices.Add(Location - Up);
+		Vertices.Add(Location + Up);
+		Normals.Add(Right);
+		Normals.Add(Right);
+		UVs.Add(FVector2D(U, 0.0f));
+		UVs.Add(FVector2D(U, 1.0f));
+
+		// Horizontal ribbon (visible from above/below)
+		Vertices.Add(Location - Right * LineHalfWidth);
+		Vertices.Add(Location + Right * LineHalfWidth);
+		Normals.Add(FVector::UpVector);
+		Normals.Add(FVector::UpVector);
+		UVs.Add(FVector2D(U, 0.0f));
+		UVs.Add(FVector2D(U, 1.0f));
+	}
+
+	// Generate triangles for both ribbons (double-sided)
+	Triangles.Reserve((NumSamples - 1) * 24);
+	for (int32 i = 0; i < NumSamples - 1; i++)
+	{
+		// Vertical ribbon indices
+		const int32 V0 = i * 4;
+		const int32 V1 = i * 4 + 1;
+		const int32 V2 = (i + 1) * 4;
+		const int32 V3 = (i + 1) * 4 + 1;
+
+		// Horizontal ribbon indices
+		const int32 H0 = i * 4 + 2;
+		const int32 H1 = i * 4 + 3;
+		const int32 H2 = (i + 1) * 4 + 2;
+		const int32 H3 = (i + 1) * 4 + 3;
+
+		// Vertical: front + back
+		Triangles.Add(V0); Triangles.Add(V2); Triangles.Add(V1);
+		Triangles.Add(V1); Triangles.Add(V2); Triangles.Add(V3);
+		Triangles.Add(V0); Triangles.Add(V1); Triangles.Add(V2);
+		Triangles.Add(V1); Triangles.Add(V3); Triangles.Add(V2);
+
+		// Horizontal: front + back
+		Triangles.Add(H0); Triangles.Add(H2); Triangles.Add(H1);
+		Triangles.Add(H1); Triangles.Add(H2); Triangles.Add(H3);
+		Triangles.Add(H0); Triangles.Add(H1); Triangles.Add(H2);
+		Triangles.Add(H1); Triangles.Add(H3); Triangles.Add(H2);
+	}
+
+	SplineMeshComp->ClearAllMeshSections();
+	SplineMeshComp->CreateMeshSection(0, Vertices, Triangles, Normals, UVs, TArray<FColor>(), TArray<FProcMeshTangent>(), false);
+
+	// Apply the current material (normal or selected)
+	// Check if handles are visible as a proxy for "selected" state
+	const bool bCurrentlySelected = (PointHandles.Num() > 0 && PointHandles[0] && PointHandles[0]->IsVisible());
+	UMaterialInstanceDynamic* LineMat = (bCurrentlySelected && SplineMatSelected) ? SplineMatSelected : SplineMat;
+	if (LineMat)
+	{
+		SplineMeshComp->SetMaterial(0, LineMat);
+	}
+
+	UpdateCenterCube();
+}
+
+void APS_Editor_SplineActor::UpdateCenterCube()
+{
+	if (!CenterCube) return;
+
+	const int32 Num = GetNumPoints();
+	if (Num == 0)
+	{
+		CenterCube->SetVisibility(false);
+		return;
+	}
+
+	// Position at centroid of all points
+	FVector Centroid = FVector::ZeroVector;
+	for (int32 i = 0; i < Num; i++)
+	{
+		Centroid += GetPointLocation(i);
+	}
+	Centroid /= Num;
+	CenterCube->SetWorldLocation(Centroid);
+	CenterCube->SetVisibility(true);
+}
+
+// ---- Handle interaction ----
+
+UStaticMeshComponent* APS_Editor_SplineActor::CreatePointHandle(const FVector& WorldPosition)
+{
+	UStaticMeshComponent* Handle = NewObject<UStaticMeshComponent>(this);
+	Handle->SetupAttachment(HandleRoot);
+	Handle->RegisterComponent();
+
+	// Load sphere mesh
+	UStaticMesh* SphereMesh = LoadObject<UStaticMesh>(nullptr, TEXT("/Engine/BasicShapes/Sphere.Sphere"));
+	if (SphereMesh)
+	{
+		Handle->SetStaticMesh(SphereMesh);
+	}
+
+	Handle->SetWorldLocation(WorldPosition);
+	Handle->SetWorldScale3D(FVector(HandleScale));
+
+	// Collision for raycast
+	Handle->SetCollisionEnabled(ECollisionEnabled::QueryOnly);
+	Handle->SetCollisionResponseToAllChannels(ECR_Ignore);
+	Handle->SetCollisionResponseToChannel(ECC_Visibility, ECR_Block);
+
+	Handle->SetCastShadow(false);
+	Handle->SetRenderInDepthPass(false);
+
+	if (HandleMat)
+	{
+		Handle->SetMaterial(0, HandleMat);
+	}
+
+	return Handle;
+}
+
+void APS_Editor_SplineActor::RebuildHandles()
+{
+	// Destroy existing handles
+	for (UStaticMeshComponent* Handle : PointHandles)
+	{
+		if (Handle)
+		{
+			Handle->DestroyComponent();
+		}
+	}
+	PointHandles.Empty();
+
+	// Create new handles at each point
+	const int32 Num = GetNumPoints();
+	for (int32 i = 0; i < Num; i++)
+	{
+		UStaticMeshComponent* Handle = CreatePointHandle(GetPointLocation(i));
+		PointHandles.Add(Handle);
+	}
+}
+
+int32 APS_Editor_SplineActor::GetHandleIndexUnderCursor(const FVector& RayOrigin, const FVector& RayDirection, float SphereRadius) const
+{
+	int32 BestIndex = -1;
+	float BestDist = MAX_FLT;
+
+	for (int32 i = 0; i < PointHandles.Num(); i++)
+	{
+		if (!PointHandles[i] || !PointHandles[i]->IsVisible()) continue;
+
+		const FVector HandlePos = PointHandles[i]->GetComponentLocation();
+
+		// Sphere-ray intersection
+		const FVector ToHandle = HandlePos - RayOrigin;
+		const float Proj = FVector::DotProduct(ToHandle, RayDirection);
+		if (Proj < 0.0f) continue; // Behind camera
+
+		const FVector ClosestPoint = RayOrigin + RayDirection * Proj;
+		const float Dist = FVector::Dist(ClosestPoint, HandlePos);
+
+		if (Dist < SphereRadius && Proj < BestDist)
+		{
+			BestDist = Proj;
+			BestIndex = i;
+		}
+	}
+
+	return BestIndex;
+}
+
+void APS_Editor_SplineActor::SetHandlesVisible(bool bVisible)
+{
+	for (UStaticMeshComponent* Handle : PointHandles)
+	{
+		if (Handle)
+		{
+			Handle->SetVisibility(bVisible);
+			Handle->SetCollisionEnabled(bVisible ? ECollisionEnabled::QueryOnly : ECollisionEnabled::NoCollision);
+		}
+	}
+}
+
+void APS_Editor_SplineActor::HighlightHandle(int32 Index)
+{
+	for (int32 i = 0; i < PointHandles.Num(); i++)
+	{
+		if (PointHandles[i])
+		{
+			PointHandles[i]->SetMaterial(0, (i == Index) ? HandleHighlightMat : HandleMat);
+		}
+	}
+}
+
+void APS_Editor_SplineActor::ClearHandleHighlight()
+{
+	for (UStaticMeshComponent* Handle : PointHandles)
+	{
+		if (Handle && HandleMat)
+		{
+			Handle->SetMaterial(0, HandleMat);
+		}
+	}
+}
+
+void APS_Editor_SplineActor::SetSelected(bool bSelected)
+{
+	// Swap line material: depth-tested (normal) vs no-depth-test (on top when selected)
+	if (SplineMeshComp)
+	{
+		UMaterialInstanceDynamic* Mat = bSelected ? SplineMatSelected : SplineMat;
+		if (Mat)
+		{
+			SplineMeshComp->SetMaterial(0, Mat);
+		}
+	}
+
+	// Center cube: bright when selected
+	if (CenterCubeMat)
+	{
+		const FLinearColor Color = bSelected ? FLinearColor(1.0f, 0.8f, 0.0f) : FLinearColor(1.0f, 0.4f, 0.0f);
+		CenterCubeMat->SetVectorParameterValue(TEXT("Color"), Color);
+	}
+}
+
+bool APS_Editor_SplineActor::IsCenterCube(const UPrimitiveComponent* Comp) const
+{
+	return Comp && Comp == CenterCube;
+}
+
+FVector APS_Editor_SplineActor::GetCentroid() const
+{
+	const int32 Num = GetNumPoints();
+	if (Num == 0) return GetActorLocation();
+
+	FVector Centroid = FVector::ZeroVector;
+	for (int32 i = 0; i < Num; i++)
+	{
+		Centroid += GetPointLocation(i);
+	}
+	return Centroid / Num;
+}
+
+// ---- Serialization ----
+
+void APS_Editor_SplineActor::ExportToCustomProperties(TMap<FString, FString>& OutProperties) const
+{
+	const int32 Num = GetNumPoints();
+	OutProperties.Add(TEXT("SplinePointCount"), FString::FromInt(Num));
+
+	for (int32 i = 0; i < Num; i++)
+	{
+		const FVector Loc = GetPointLocation(i);
+		OutProperties.Add(
+			FString::Printf(TEXT("SplinePoint_%d"), i),
+			FString::Printf(TEXT("X=%.4f Y=%.4f Z=%.4f"), Loc.X, Loc.Y, Loc.Z));
+	}
+}
+
+void APS_Editor_SplineActor::ImportFromCustomProperties(const TMap<FString, FString>& Properties)
+{
+	const FString* CountStr = Properties.Find(TEXT("SplinePointCount"));
+	if (!CountStr) return;
+
+	const int32 Num = FCString::Atoi(**CountStr);
+	if (Num < 2) return;
+
+	TArray<FVector> Points;
+	for (int32 i = 0; i < Num; i++)
+	{
+		const FString Key = FString::Printf(TEXT("SplinePoint_%d"), i);
+		const FString* ValStr = Properties.Find(Key);
+		if (!ValStr) continue;
+
+		FVector Loc;
+		if (Loc.InitFromString(*ValStr))
+		{
+			Points.Add(Loc);
+		}
+	}
+
+	if (Points.Num() >= 2)
+	{
+		SetAllPointLocations(Points);
+	}
+}

Unreal/Plugins/PS_Editor/Source/PS_Editor/Spline/PS_Editor_SplineActor.h

@@ -0,0 +1,130 @@
+#pragma once
+
+#include "CoreMinimal.h"
+#include "GameFramework/Actor.h"
+#include "PS_Editor_SplineActor.generated.h"
+
+class USplineComponent;
+class UProceduralMeshComponent;
+
+/**
+ * Runtime spline actor for path/route editing in PS_Editor.
+ * Renders as a visible quad strip with clickable point handles.
+ */
+UCLASS()
+class PS_EDITOR_API APS_Editor_SplineActor : public AActor
+{
+	GENERATED_BODY()
+
+public:
+	APS_Editor_SplineActor();
+
+	// ---- Point manipulation ----
+
+	/** Add a point at the end of the spline (world space). */
+	void AddPoint(const FVector& WorldPosition);
+
+	/** Move an existing point to a new world position. */
+	void MovePoint(int32 Index, const FVector& NewWorldPosition);
+
+	/** Remove a point by index. */
+	void RemovePoint(int32 Index);
+
+	/** Get the number of spline points. */
+	int32 GetNumPoints() const;
+
+	/** Get the world position of a spline point. */
+	FVector GetPointLocation(int32 Index) const;
+
+	/** Get all point world positions (for undo snapshots). */
+	TArray<FVector> GetAllPointLocations() const;
+
+	/** Set all point positions at once (for undo restore). Rebuilds handles and visualization. */
+	void SetAllPointLocations(const TArray<FVector>& Points);
+
+	// ---- Visualization ----
+
+	/** Regenerate the line mesh and reposition all handles. */
+	void UpdateVisualization();
+
+	// ---- Handle interaction ----
+
+	/** Find which point handle is under the cursor ray. Returns -1 if none. */
+	int32 GetHandleIndexUnderCursor(const FVector& RayOrigin, const FVector& RayDirection, float SphereRadius = 15.0f) const;
+
+	/** Show or hide all point handles and center cube. */
+	void SetHandlesVisible(bool bVisible);
+
+	/** Set the spline's selected state (changes line + cube color). */
+	void SetSelected(bool bSelected);
+
+	/** Returns true if the given component is the center cube. */
+	bool IsCenterCube(const UPrimitiveComponent* Comp) const;
+
+	/** Highlight a specific handle (yellow), others go back to normal (white). */
+	void HighlightHandle(int32 Index);
+
+	/** Clear all handle highlights. */
+	void ClearHandleHighlight();
+
+	// ---- Serialization ----
+
+	/** Get the centroid of all spline points (world space). Used as pivot for gizmo. */
+	FVector GetCentroid() const;
+
+	/** Export spline data to a key-value map (for JSON serialization). */
+	void ExportToCustomProperties(TMap<FString, FString>& OutProperties) const;
+
+	/** Import spline data from a key-value map (for scene loading). */
+	void ImportFromCustomProperties(const TMap<FString, FString>& Properties);
+
+protected:
+	virtual void BeginPlay() override;
+
+private:
+	UPROPERTY(VisibleAnywhere)
+	TObjectPtr<USplineComponent> SplineComp;
+
+	UPROPERTY(VisibleAnywhere)
+	TObjectPtr<UProceduralMeshComponent> SplineMeshComp;
+
+	UPROPERTY(VisibleAnywhere)
+	TObjectPtr<USceneComponent> HandleRoot;
+
+	UPROPERTY()
+	TArray<TObjectPtr<UStaticMeshComponent>> PointHandles;
+
+	// Materials
+	UPROPERTY()
+	TObjectPtr<UMaterialInstanceDynamic> SplineMat;           // Normal (depth tested)
+
+	UPROPERTY()
+	TObjectPtr<UMaterialInstanceDynamic> SplineMatSelected;   // Selected (no depth test, on top)
+
+	UPROPERTY()
+	TObjectPtr<UMaterialInstanceDynamic> HandleMat;
+
+	UPROPERTY()
+	TObjectPtr<UMaterialInstanceDynamic> HandleHighlightMat;
+
+	UPROPERTY()
+	TObjectPtr<UStaticMeshComponent> CenterCube;
+
+	/** Create a handle sphere for a point at the given world position. */
+	UStaticMeshComponent* CreatePointHandle(const FVector& WorldPosition);
+
+	/** Rebuild all handles from current spline points. */
+	void RebuildHandles();
+
+	/** Update center cube position to the centroid of all points. */
+	void UpdateCenterCube();
+
+	UPROPERTY()
+	TObjectPtr<UMaterialInstanceDynamic> CenterCubeMat;
+
+	/** Line rendering settings. */
+	float LineHalfWidth = 2.0f;
+	float SampleInterval = 10.0f;
+	float HandleScale = 0.12f;
+	float CenterCubeScale = 0.10f;
+};

Unreal/Plugins/PS_Editor/Source/PS_Editor/UI/Widgets/PS_Editor_MainWidget.cpp

@@ -6,6 +6,7 @@
 #include "PS_Editor_PlayerController.h"
 #include "PS_Editor_EditableComponent.h"
 #include "PS_Editor_SpawnableComponent.h"
+#include "PS_Editor_SplineActor.h"
 #include "Widgets/SBoxPanel.h"
 #include "Widgets/Text/STextBlock.h"
 #include "Widgets/Layout/SBorder.h"
@@ -239,6 +240,31 @@ TSharedRef<SWidget> UPS_Editor_MainWidget::BuildToolbar()
 					})
 				]
 			]
+			// New Spline button
+			+ SHorizontalBox::Slot().AutoWidth().Padding(8.0f, 0.0f, 2.0f, 0.0f)
+			[
+				SNew(SButton)
+				.OnClicked_Lambda([this]() -> FReply
+				{
+					if (APS_Editor_PlayerController* EditorPC = Cast<APS_Editor_PlayerController>(GetOwningPlayer()))
+					{
+						if (EditorPC->GetEditorMode() == EPS_Editor_EditorMode::SplinePlacement)
+						{
+							EditorPC->FinishSplinePlacement();
+						}
+						else
+						{
+							EditorPC->BeginSplinePlacement();
+						}
+					}
+					return FReply::Handled();
+				})
+				[
+					SNew(STextBlock)
+					.Text(FText::FromString(TEXT("New Spline (S)")))
+					.Font(FCoreStyle::GetDefaultFontStyle("Regular", 10))
+				]
+			]
 		];
 }
 
@@ -685,14 +711,28 @@ void UPS_Editor_MainWidget::RefreshPropertiesFromSelection()
 	// Update mode text
 	if (ModeText.IsValid())
 	{
-		FString ModeStr;
-		switch (SM->GetTransformMode())
+		// Check for spline placement mode first
+		bool bSplineMode = false;
+		if (APS_Editor_PlayerController* EditorPC = Cast<APS_Editor_PlayerController>(GetOwningPlayer()))
 		{
-		case EPS_Editor_TransformMode::Translate: ModeStr = TEXT("Translate (Z)"); break;
-		case EPS_Editor_TransformMode::Rotate:    ModeStr = TEXT("Rotate (E)"); break;
-		case EPS_Editor_TransformMode::Scale:     ModeStr = TEXT("Scale (R)"); break;
+			if (EditorPC->GetEditorMode() == EPS_Editor_EditorMode::SplinePlacement)
+			{
+				ModeText->SetText(FText::FromString(TEXT("Spline Placement (click to add, RMB/Enter to finish, Esc to cancel)")));
+				bSplineMode = true;
+			}
+		}
+
+		if (!bSplineMode)
+		{
+			FString ModeStr;
+			switch (SM->GetTransformMode())
+			{
+			case EPS_Editor_TransformMode::Translate: ModeStr = TEXT("Translate (Z)"); break;
+			case EPS_Editor_TransformMode::Rotate:    ModeStr = TEXT("Rotate (E)"); break;
+			case EPS_Editor_TransformMode::Scale:     ModeStr = TEXT("Scale (R)"); break;
+			}
+			ModeText->SetText(FText::FromString(ModeStr));
 		}
-		ModeText->SetText(FText::FromString(ModeStr));
 	}
 
 	// Update space button text
@@ -877,16 +917,17 @@ void UPS_Editor_MainWidget::RefreshOutliner()
 		AActor* Actor = SpawnedActors[i].Get();
 		if (!Actor || Actor->IsHidden()) continue;
 
-		// Build display name: SpawnableComponent DisplayName > Class name (cleaned)
+		// Build display name
 		FString DisplayName;
-		if (UActorComponent* SpawnComp = Actor->FindComponentByClass(UPS_Editor_SpawnableComponent::StaticClass()))
+		if (Cast<APS_Editor_SplineActor>(Actor))
 		{
-			if (UPS_Editor_SpawnableComponent* SC = Cast<UPS_Editor_SpawnableComponent>(SpawnComp))
+			DisplayName = TEXT("Spline");
+		}
+		else if (UPS_Editor_SpawnableComponent* SC = Actor->FindComponentByClass<UPS_Editor_SpawnableComponent>())
+		{
+			if (!SC->DisplayName.IsEmpty())
 			{
-				if (!SC->DisplayName.IsEmpty())
-				{
-					DisplayName = SC->DisplayName;
-				}
+				DisplayName = SC->DisplayName;
 			}
 		}
 		if (DisplayName.IsEmpty())