Loading screen overlay + camera fade on sublevel load

- Add loading overlay (black background + "Loading..." text) behind UI panels
- Overlay starts visible by default, hidden in NativeConstruct if no sublevel
- CameraFade to black before sublevel load, with deferred fallback for BeginPlay
- 2s delay after OnLevelShown before starting 2s fade-in from black
- ShowLoadingScreen helper on PlayerController via HUD->MainWidget

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

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

@@ -11,6 +11,9 @@
 #include "Engine/LevelStreamingDynamic.h"
 #include "Engine/PostProcessVolume.h"
 #include "PS_Editor_CameraStart.h"
+#include "PS_Editor_HUD.h"
+#include "PS_Editor_MainWidget.h"
+#include "Camera/PlayerCameraManager.h"
 #include "PS_Editor_GameInstanceSubsystem.h"
 #include "GameFramework/GameModeBase.h"
 #include "GameFramework/GameStateBase.h"
@@ -136,6 +139,14 @@ void APS_Editor_PlayerController::Tick(float DeltaTime)
 {
 	Super::Tick(DeltaTime);
 
+	// Deferred fade-to-black: CameraManager wasn't ready at BeginPlay
+	if (bPendingFadeToBlack && PlayerCameraManager)
+	{
+		PlayerCameraManager->StartCameraFade(0.0f, 1.0f, 0.0f, FLinearColor::Black, true, true);
+		bPendingFadeToBlack = false;
+		ShowLoadingScreen(true);
+	}
+
 	if (SpawnManager)
 	{
 		SpawnManager->TickEditorMode(DeltaTime);
@@ -253,6 +264,17 @@ void APS_Editor_PlayerController::CancelPointPlacement()
 	FinishPointPlacement();
 }
 
+void APS_Editor_PlayerController::ShowLoadingScreen(bool bShow)
+{
+	if (APS_Editor_HUD* EditorHUD = Cast<APS_Editor_HUD>(GetHUD()))
+	{
+		if (UPS_Editor_MainWidget* Widget = EditorHUD->GetMainWidget())
+		{
+			Widget->ShowLoadingScreen(bShow);
+		}
+	}
+}
+
 void APS_Editor_PlayerController::LoadBaseLevelAsSublevel(const FString& LevelName, const FString& MapPath)
 {
 	// Unload previous sublevel first
@@ -294,6 +316,19 @@ void APS_Editor_PlayerController::LoadBaseLevelAsSublevel(const FString& LevelNa
 		return;
 	}
 
+	// Fade to black + show loading overlay
+	bWaitingForSublevelFadeIn = true;
+	if (PlayerCameraManager)
+	{
+		PlayerCameraManager->StartCameraFade(0.0f, 1.0f, 0.0f, FLinearColor::Black, true, true);
+		bPendingFadeToBlack = false;
+	}
+	else
+	{
+		bPendingFadeToBlack = true;
+	}
+	ShowLoadingScreen(true);
+
 	// Use MapPath if provided, otherwise fall back to LevelName (legacy behavior)
 	const FString& LevelToLoad = MapPath.IsEmpty() ? LevelName : MapPath;
 
@@ -362,6 +397,21 @@ void APS_Editor_PlayerController::DisableSublevelPostProcessMaterials()
 				*CameraStart->GetActorLocation().ToString());
 		}
 	}
+
+	// Delay 2s then fade in from black over 2 seconds
+	if (bWaitingForSublevelFadeIn)
+	{
+		bWaitingForSublevelFadeIn = false;
+		FTimerHandle FadeTimer;
+		GetWorldTimerManager().SetTimer(FadeTimer, [this]()
+		{
+			ShowLoadingScreen(false);
+			if (PlayerCameraManager)
+			{
+				PlayerCameraManager->StartCameraFade(1.0f, 0.0f, 2.0f, FLinearColor::Black, false, false);
+			}
+		}, 2.0f, false);
+	}
 }
 
 void APS_Editor_PlayerController::HandleEditorClick(FVector2D ScreenPos, bool bAdditive)

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

@@ -136,9 +136,18 @@ private:
 	UPROPERTY()
 	TObjectPtr<ULevelStreamingDynamic> CurrentSublevel;
 
+	/** True when a sublevel is loading and needs fade-in when ready. */
+	bool bWaitingForSublevelFadeIn = false;
+
+	/** True if we need to apply the fade-to-black once CameraManager is available. */
+	bool bPendingFadeToBlack = false;
+
 	/** Disable custom post-process materials in the loaded sublevel to avoid stencil conflicts. */
 	UFUNCTION()
 	void DisableSublevelPostProcessMaterials();
 
+	/** Show/hide loading screen overlay on the HUD widget. */
+	void ShowLoadingScreen(bool bShow);
+
 	void HandleEditorClick(FVector2D ScreenPos, bool bAdditive);
 };

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

@@ -45,6 +45,27 @@ void UPS_Editor_MainWidget::SetSceneSerializer(UPS_Editor_SceneSerializer* InSer
 TSharedRef<SWidget> UPS_Editor_MainWidget::RebuildWidget()
 {
 	return SNew(SOverlay)
+		// Loading screen (behind everything — first slot = bottom layer)
+		+ SOverlay::Slot()
+		.HAlign(HAlign_Fill)
+		.VAlign(VAlign_Fill)
+		[
+			SAssignNew(LoadingOverlay, SBorder)
+			.Visibility(EVisibility::Visible)
+			.BorderImage(FCoreStyle::Get().GetBrush("WhiteBrush"))
+			.BorderBackgroundColor(FLinearColor(0.0f, 0.0f, 0.0f, 1.0f))
+			[
+				SNew(SBox)
+				.HAlign(HAlign_Center)
+				.VAlign(VAlign_Center)
+				[
+					SNew(STextBlock)
+					.Text(FText::FromString(TEXT("Loading...")))
+					.Font(FCoreStyle::GetDefaultFontStyle("Bold", 18))
+					.ColorAndOpacity(FLinearColor(0.7f, 0.7f, 0.7f, 1.0f))
+				]
+			]
+		]
 		// Top-left: Title + Toolbar
 		+ SOverlay::Slot()
 		.HAlign(HAlign_Left)
@@ -999,6 +1020,19 @@ void UPS_Editor_MainWidget::NativeConstruct()
 	}
 
 	PopulateSceneList();
+
+	// Hide loading overlay if no sublevel is being loaded
+	if (APS_Editor_PlayerController* PC = Cast<APS_Editor_PlayerController>(GetOwningPlayer()))
+	{
+		if (PC->CurrentBaseLevel.IsEmpty())
+		{
+			ShowLoadingScreen(false);
+		}
+	}
+	else
+	{
+		ShowLoadingScreen(false);
+	}
 }
 
 void UPS_Editor_MainWidget::PopulateSceneList()
@@ -2184,6 +2218,14 @@ void UPS_Editor_MainWidget::OnModeButtonClicked(EPS_Editor_TransformMode Mode)
 	}
 }
 
+void UPS_Editor_MainWidget::ShowLoadingScreen(bool bShow)
+{
+	if (LoadingOverlay.IsValid())
+	{
+		LoadingOverlay->SetVisibility(bShow ? EVisibility::Visible : EVisibility::Collapsed);
+	}
+}
+
 void UPS_Editor_MainWidget::OnCloseClicked()
 {
 	if (CloseConfirmOverlay.IsValid())

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

@@ -110,6 +110,13 @@ private:
 	bool bSceneDirty = false;
 	int32 LastKnownSpawnedCount = 0;
 
+	// Loading screen
+	TSharedPtr<SWidget> LoadingOverlay;
+
+public:
+	/** Show/hide the loading overlay. */
+	void ShowLoadingScreen(bool bShow);
+
 	// ---- Helpers ----
 	TSharedRef<SWidget> BuildToolbar();
 	TSharedRef<SWidget> BuildPropertiesPanel();