Add snap to ground, screen-space rotate/scale, and input refinements

- End key snaps selected actors to ground (downward trace + bounds offset)
- Rotate/Scale now use screen-space mouse delta (X+Y combined) for intuitive control
- Accumulator-based drag for smooth incremental rotation and scaling
- Fixed rotation drag plane (perpendicular to axis instead of parallel)
- Movement: arrows + A (up) / Q (down), letter keys freed for hotkeys

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

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

@@ -168,6 +168,10 @@ void APS_Editor_Pawn::CreateInputActions()
 	IA_Delete = NewObject<UInputAction>(this, TEXT("IA_Delete"));
 	IA_Delete->ValueType = EInputActionValueType::Boolean;
 	EditorMappingContext->MapKey(IA_Delete, EKeys::Delete);
+
+	IA_SnapToGround = NewObject<UInputAction>(this, TEXT("IA_SnapToGround"));
+	IA_SnapToGround->ValueType = EInputActionValueType::Boolean;
+	EditorMappingContext->MapKey(IA_SnapToGround, EKeys::End);
 }
 
 void APS_Editor_Pawn::SetupPlayerInputComponent(UInputComponent* PlayerInputComponent)
@@ -205,6 +209,7 @@ void APS_Editor_Pawn::SetupPlayerInputComponent(UInputComponent* PlayerInputComp
 	EIC->BindAction(IA_RotateMode, ETriggerEvent::Started, this, &APS_Editor_Pawn::HandleRotateMode);
 	EIC->BindAction(IA_ScaleMode, ETriggerEvent::Started, this, &APS_Editor_Pawn::HandleScaleMode);
 	EIC->BindAction(IA_Delete, ETriggerEvent::Started, this, &APS_Editor_Pawn::HandleDelete);
+	EIC->BindAction(IA_SnapToGround, ETriggerEvent::Started, this, &APS_Editor_Pawn::HandleSnapToGround);
 }
 
 // ---- Input Handlers ----
@@ -290,19 +295,6 @@ void APS_Editor_Pawn::HandleLook(const FInputActionValue& Value)
 	}
 	else if (CameraMode == EPS_Editor_CameraMode::GizmoDrag)
 	{
-		// Intersect mouse ray with drag plane, constrain delta to axis, apply to actors
-		FVector RayOrigin, RayDir;
-		if (!GetMouseWorldRay(RayOrigin, RayDir))
-		{
-			return;
-		}
-
-		FVector CurrentIntersection;
-		if (!RayPlaneIntersection(RayOrigin, RayDir, GizmoDragPlaneOrigin, GizmoDragPlaneNormal, CurrentIntersection))
-		{
-			return;
-		}
-
 		APS_Editor_PlayerController* EditorPC = Cast<APS_Editor_PlayerController>(GetController());
 		if (!EditorPC) return;
 		UPS_Editor_SelectionManager* SM = EditorPC->GetSelectionManager();
@@ -311,14 +303,20 @@ void APS_Editor_Pawn::HandleLook(const FInputActionValue& Value)
 		if (!Gizmo) return;
 
 		const FVector AxisDir = Gizmo->GetAxisDirection(ActiveGizmoAxis);
-		const FVector TotalDelta = CurrentIntersection - GizmoDragInitialIntersection;
 		const EPS_Editor_TransformMode Mode = SM->GetTransformMode();
-
 		const TArray<TWeakObjectPtr<AActor>>& Selected = SM->GetSelectedActors();
 
 		if (Mode == EPS_Editor_TransformMode::Translate)
 		{
+			// Ray-plane intersection for precise axis-constrained translation
+			FVector RayOrigin, RayDir;
+			if (!GetMouseWorldRay(RayOrigin, RayDir)) return;
+			FVector CurrentIntersection;
+			if (!RayPlaneIntersection(RayOrigin, RayDir, GizmoDragPlaneOrigin, GizmoDragPlaneNormal, CurrentIntersection)) return;
+
+			const FVector TotalDelta = CurrentIntersection - GizmoDragInitialIntersection;
 			const FVector ConstrainedDelta = FVector::DotProduct(TotalDelta, AxisDir) * AxisDir;
+
 			for (int32 i = 0; i < Selected.Num() && i < GizmoDragInitialTransforms.Num(); ++i)
 			{
 				if (AActor* Actor = Selected[i].Get())
@@ -329,29 +327,23 @@ void APS_Editor_Pawn::HandleLook(const FInputActionValue& Value)
 		}
 		else if (Mode == EPS_Editor_TransformMode::Rotate)
 		{
-			// Compute rotation angle from initial to current intersection around the axis
+			// Use combined mouse X+Y screen movement to drive rotation angle
+			const float RotationSpeed = 1.0f;
+			const float AngleDelta = (LookInput.X + LookInput.Y) * RotationSpeed;
+
+			// Accumulate total angle since drag start
+			GizmoDragAccumulator += AngleDelta;
+
+			const FQuat RotationQuat(AxisDir, FMath::DegreesToRadians(GizmoDragAccumulator));
 			const FVector GizmoLoc = GizmoDragPlaneOrigin;
-			const FVector InitDir = (GizmoDragInitialIntersection - GizmoLoc).GetSafeNormal();
-			const FVector CurrDir = (CurrentIntersection - GizmoLoc).GetSafeNormal();
-
-			// Signed angle via cross product
-			float Angle = FMath::Atan2(
-				FVector::DotProduct(FVector::CrossProduct(InitDir, CurrDir), AxisDir),
-				FVector::DotProduct(InitDir, CurrDir));
-			Angle = FMath::RadiansToDegrees(Angle);
-
-			const FQuat RotationQuat(AxisDir, FMath::DegreesToRadians(Angle));
 
 			for (int32 i = 0; i < Selected.Num() && i < GizmoDragInitialTransforms.Num(); ++i)
 			{
 				if (AActor* Actor = Selected[i].Get())
 				{
-					// Rotate around gizmo pivot
 					const FVector Offset = GizmoDragInitialTransforms[i].GetLocation() - GizmoLoc;
-					const FVector RotatedOffset = RotationQuat.RotateVector(Offset);
-					Actor->SetActorLocation(GizmoLoc + RotatedOffset);
+					Actor->SetActorLocation(GizmoLoc + RotationQuat.RotateVector(Offset));
 
-					// Also rotate the actor itself
 					const FQuat OrigRot = GizmoDragInitialTransforms[i].GetRotation();
 					Actor->SetActorRotation((RotationQuat * OrigRot).Rotator());
 				}
@@ -359,22 +351,17 @@ void APS_Editor_Pawn::HandleLook(const FInputActionValue& Value)
 		}
 		else if (Mode == EPS_Editor_TransformMode::Scale)
 		{
-			// Scale factor from mouse movement along the axis
-			const float InitialDist = FVector::DotProduct(GizmoDragInitialIntersection - GizmoDragPlaneOrigin, AxisDir);
-			const float CurrentDist = FVector::DotProduct(CurrentIntersection - GizmoDragPlaneOrigin, AxisDir);
+			// Use combined mouse X+Y screen movement to drive scale
+			const float ScaleSpeed = 0.01f;
+			GizmoDragAccumulator += (LookInput.X + LookInput.Y) * ScaleSpeed;
 
-			float ScaleFactor = 1.0f;
-			if (FMath::Abs(InitialDist) > KINDA_SMALL_NUMBER)
-			{
-				ScaleFactor = FMath::Clamp(CurrentDist / InitialDist, 0.01f, 100.0f);
-			}
+			const float ScaleFactor = FMath::Clamp(1.0f + GizmoDragAccumulator, 0.01f, 100.0f);
 
 			for (int32 i = 0; i < Selected.Num() && i < GizmoDragInitialTransforms.Num(); ++i)
 			{
 				if (AActor* Actor = Selected[i].Get())
 				{
 					FVector NewScale = GizmoDragInitialTransforms[i].GetScale3D();
-					// Scale only on the dragged axis
 					if (ActiveGizmoAxis == EPS_Editor_GizmoAxis::X) NewScale.X *= ScaleFactor;
 					else if (ActiveGizmoAxis == EPS_Editor_GizmoAxis::Y) NewScale.Y *= ScaleFactor;
 					else if (ActiveGizmoAxis == EPS_Editor_GizmoAxis::Z) NewScale.Z *= ScaleFactor;
@@ -383,7 +370,6 @@ void APS_Editor_Pawn::HandleLook(const FInputActionValue& Value)
 			}
 		}
 
-		// Update gizmo position
 		Gizmo->SetActorLocation(SM->GetSelectionPivot());
 	}
 }
@@ -548,6 +534,18 @@ void APS_Editor_Pawn::HandleDelete(const FInputActionValue& Value)
 	}
 }
 
+void APS_Editor_Pawn::HandleSnapToGround(const FInputActionValue& Value)
+{
+	if (CameraMode != EPS_Editor_CameraMode::Idle) return;
+	if (APS_Editor_PlayerController* EditorPC = Cast<APS_Editor_PlayerController>(GetController()))
+	{
+		if (UPS_Editor_SelectionManager* SM = EditorPC->GetSelectionManager())
+		{
+			SM->SnapSelectionToGround();
+		}
+	}
+}
+
 // ---- Helpers ----
 
 void APS_Editor_Pawn::SetCameraMode(EPS_Editor_CameraMode NewMode)
@@ -684,21 +682,30 @@ void APS_Editor_Pawn::BeginGizmoDrag(EPS_Editor_GizmoAxis Axis)
 
 	ActiveGizmoAxis = Axis;
 
-	// Get the axis direction in world space
 	const FVector AxisDir = Gizmo->GetAxisDirection(Axis);
+	const EPS_Editor_TransformMode Mode = SM->GetTransformMode();
 
-	// Compute the drag plane: contains the axis and faces the camera as much as possible
-	const FVector CameraForward = GetActorForwardVector();
-	FVector PlaneNormal = FVector::CrossProduct(AxisDir, CameraForward).GetSafeNormal();
-	if (PlaneNormal.IsNearlyZero())
+	FVector PlaneNormal;
+	if (Mode == EPS_Editor_TransformMode::Rotate)
 	{
-		// Camera looking along the axis - use camera up instead
-		PlaneNormal = FVector::CrossProduct(AxisDir, FVector::UpVector).GetSafeNormal();
+		// For rotation: plane perpendicular to the rotation axis
+		PlaneNormal = AxisDir;
+	}
+	else
+	{
+		// For translate/scale: plane containing the axis, facing the camera
+		const FVector CameraForward = GetActorForwardVector();
+		PlaneNormal = FVector::CrossProduct(AxisDir, CameraForward).GetSafeNormal();
+		if (PlaneNormal.IsNearlyZero())
+		{
+			PlaneNormal = FVector::CrossProduct(AxisDir, FVector::UpVector).GetSafeNormal();
+		}
+		PlaneNormal = FVector::CrossProduct(AxisDir, PlaneNormal).GetSafeNormal();
 	}
-	PlaneNormal = FVector::CrossProduct(AxisDir, PlaneNormal).GetSafeNormal();
 
 	GizmoDragPlaneNormal = PlaneNormal;
 	GizmoDragPlaneOrigin = Gizmo->GetActorLocation();
+	GizmoDragAccumulator = 0.0f;
 
 	// Get initial mouse-plane intersection
 	FVector RayOrigin, RayDir;

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

@@ -158,6 +158,9 @@ private:
 	UPROPERTY()
 	TObjectPtr<UInputAction> IA_Delete;
 
+	UPROPERTY()
+	TObjectPtr<UInputAction> IA_SnapToGround;
+
 	// ---- Modifier key state ----
 	bool bAltHeld = false;
 	bool bCtrlHeld = false;
@@ -171,6 +174,7 @@ private:
 	FVector GizmoDragPlaneOrigin = FVector::ZeroVector;
 	FVector GizmoDragInitialIntersection = FVector::ZeroVector;
 	TArray<FTransform> GizmoDragInitialTransforms;
+	float GizmoDragAccumulator = 0.0f;
 
 	// ---- Input Handlers ----
 	void HandleMove(const FInputActionValue& Value);
@@ -186,6 +190,7 @@ private:
 	void HandleRotateMode(const FInputActionValue& Value);
 	void HandleScaleMode(const FInputActionValue& Value);
 	void HandleDelete(const FInputActionValue& Value);
+	void HandleSnapToGround(const FInputActionValue& Value);
 
 	// ---- Helpers ----
 	void CreateInputActions();

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

@@ -218,6 +218,45 @@ void UPS_Editor_SelectionManager::SetActorHighlight(AActor* Actor, bool bHighlig
 	}
 }
 
+void UPS_Editor_SelectionManager::SnapSelectionToGround()
+{
+	APlayerController* PC = OwnerPC.Get();
+	if (!PC) return;
+
+	for (const TWeakObjectPtr<AActor>& Weak : SelectedActors)
+	{
+		AActor* Actor = Weak.Get();
+		if (!Actor) continue;
+
+		// Get actor bounds to compute the bottom of the actor
+		FVector Origin, Extent;
+		Actor->GetActorBounds(false, Origin, Extent);
+		const float BottomOffset = Extent.Z; // Distance from actor origin to bottom
+
+		// Trace downward from actor location
+		const FVector Start = Actor->GetActorLocation();
+		const FVector End = Start - FVector::UpVector * 100000.0f;
+
+		FHitResult Hit;
+		FCollisionQueryParams Params;
+		Params.AddIgnoredActor(Actor);
+		Params.AddIgnoredActor(PC->GetPawn());
+		if (Gizmo) Params.AddIgnoredActor(Gizmo);
+
+		if (Actor->GetWorld()->LineTraceSingleByChannel(Hit, Start, End, ECC_Visibility, Params))
+		{
+			// Place actor so its bottom sits on the ground
+			FVector NewLocation = Hit.ImpactPoint;
+			NewLocation.Z += BottomOffset;
+			Actor->SetActorLocation(NewLocation);
+
+			UE_LOG(LogTemp, Log, TEXT("PS_Editor: Snapped %s to ground"), *Actor->GetName());
+		}
+	}
+
+	UpdateGizmo();
+}
+
 void UPS_Editor_SelectionManager::UpdateGizmo()
 {
 	if (!Gizmo)

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

@@ -36,6 +36,9 @@ public:
 	void ToggleActor(AActor* Actor);
 	void ClearSelection();
 
+	/** Snap all selected actors to the ground below them. */
+	void SnapSelectionToGround();
+
 	// ---- Queries ----
 
 	const TArray<TWeakObjectPtr<AActor>>& GetSelectedActors() const { return SelectedActors; }