Client-side smoothing for replicated body rotation

Server-only AddActorWorldRotation (HasAuthority guard) prevents
client/server tug-of-war. Client interpolates toward replicated
rotation via SmoothedBodyYaw (angle-aware FInterpTo at 3x body
speed) to eliminate step artifacts from ~30Hz network updates.
Cascade (DeltaYaw, head, eyes) uses SmoothedBodyYaw on all machines.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Unreal/PS_AI_Agent/Plugins/PS_AI_ConvAgent/Source/PS_AI_ConvAgent/Private/PS_AI_ConvAgent_PostureComponent.cpp

@@ -99,6 +99,7 @@ void UPS_AI_ConvAgent_PostureComponent::BeginPlay()
 	// Apply the mesh forward offset so "neutral" aligns with where the face points.
 	OriginalActorYaw = Owner->GetActorRotation().Yaw + MeshForwardYawOffset;
 	TargetBodyWorldYaw = Owner->GetActorRotation().Yaw;
+	SmoothedBodyYaw = Owner->GetActorRotation().Yaw;
 
 	if (bDebug)
 	{
@@ -179,6 +180,7 @@ void UPS_AI_ConvAgent_PostureComponent::ResetBodyTarget()
 	if (AActor* Owner = GetOwner())
 	{
 		TargetBodyWorldYaw = Owner->GetActorRotation().Yaw;
+		SmoothedBodyYaw = Owner->GetActorRotation().Yaw;
 	}
 }
 
@@ -328,9 +330,10 @@ void UPS_AI_ConvAgent_PostureComponent::TickComponent(
 			TargetWorldYaw = HorizontalDir.Rotation().Yaw;
 		}
 
-		// Body smoothly interpolates toward its persistent target
+		// Body smoothly interpolates toward its persistent target.
-		// (only when body tracking is enabled — otherwise only head+eyes move).
+		// Server/standalone: directly rotates the actor.
-		if (bEnableBodyTracking)
+		// Client: does NOT rotate — accepts replicated rotation from server.
+		if (bEnableBodyTracking && Owner->HasAuthority())
 		{
 			const float BodyDelta = FMath::FindDeltaAngleDegrees(
 				Owner->GetActorRotation().Yaw, TargetBodyWorldYaw);
@@ -341,12 +344,26 @@ void UPS_AI_ConvAgent_PostureComponent::TickComponent(
 			}
 		}
 
+		// ── Smoothed body yaw for cascade computations ──────────────────
+		// Server: direct copy (no lag). Client: interpolate toward replicated
+		// rotation to avoid step artifacts from discrete ~30Hz network updates.
+		if (Owner->HasAuthority())
+		{
+			SmoothedBodyYaw = Owner->GetActorRotation().Yaw;
+		}
+		else
+		{
+			const float ReplicatedYaw = Owner->GetActorRotation().Yaw;
+			const float ClientDelta = FMath::FindDeltaAngleDegrees(SmoothedBodyYaw, ReplicatedYaw);
+			SmoothedBodyYaw += FMath::FInterpTo(0.0f, ClientDelta, SafeDeltaTime, BodyInterpSpeed * 3.0f);
+		}
+
 		// ── 3. Compute DeltaYaw after body interp ──────────────────────────
 
 		float DeltaYaw = 0.0f;
 		if (!HorizontalDir.IsNearlyZero(1.0f))
 		{
-			const float CurrentFacingYaw = Owner->GetActorRotation().Yaw + MeshForwardYawOffset;
+			const float CurrentFacingYaw = SmoothedBodyYaw + MeshForwardYawOffset;
 			DeltaYaw = FMath::FindDeltaAngleDegrees(CurrentFacingYaw, TargetWorldYaw);
 		}
 
@@ -432,6 +449,7 @@ void UPS_AI_ConvAgent_PostureComponent::TickComponent(
 
 		// Body: keep current orientation — don't rotate back to original facing.
 		// The body stays wherever the last tracking left it; only head and eyes reset.
+		SmoothedBodyYaw = Owner->GetActorRotation().Yaw;
 
 		// Head + Eyes: return to center
 		TargetHeadYaw = 0.0f;
@@ -531,20 +549,21 @@ void UPS_AI_ConvAgent_PostureComponent::TickComponent(
 		DebugFrameCounter++;
 		if (DebugFrameCounter % 120 == 0)
 		{
-			const float FacingYaw = Owner->GetActorRotation().Yaw + MeshForwardYawOffset;
+			const float FacingYaw = SmoothedBodyYaw + MeshForwardYawOffset;
 			const FVector TP = TargetActor->GetActorLocation() + TargetOffset;
 			const FVector Dir = TP - Owner->GetActorLocation();
 			const float TgtYaw = FVector(Dir.X, Dir.Y, 0.0f).Rotation().Yaw;
 			const float Delta = FMath::FindDeltaAngleDegrees(FacingYaw, TgtYaw);
 
 			UE_LOG(LogPS_AI_ConvAgent_Posture, Log,
-				TEXT("Posture [%s -> %s]: Delta=%.1f | Head=%.1f/%.1f | Eyes=%.1f/%.1f | Body: enabled=%s TargetYaw=%.1f ActorYaw=%.1f"),
+				TEXT("Posture [%s -> %s]: Delta=%.1f | Head=%.1f/%.1f | Eyes=%.1f/%.1f | Body: enabled=%s TargetYaw=%.1f SmoothedYaw=%.1f (raw=%.1f)"),
 				*Owner->GetName(), *TargetActor->GetName(),
 				Delta,
 				CurrentHeadYaw, CurrentHeadPitch,
 				CurrentEyeYaw, CurrentEyePitch,
 				bEnableBodyTracking ? TEXT("Y") : TEXT("N"),
 				TargetBodyWorldYaw,
+				SmoothedBodyYaw,
 				Owner->GetActorRotation().Yaw);
 		}
 	}

Unreal/PS_AI_Agent/Plugins/PS_AI_ConvAgent/Source/PS_AI_ConvAgent/Public/PS_AI_ConvAgent_PostureComponent.h

@@ -321,6 +321,12 @@ private:
 	 *  Same sticky pattern as TargetHeadYaw but for the body layer. */
 	float TargetBodyWorldYaw = 0.0f;
 
+	/** Smoothed body yaw for cascade computations.
+	 *  On server/standalone: mirrors Owner->GetActorRotation().Yaw directly.
+	 *  On client: interpolates toward the replicated rotation to avoid
+	 *  step artifacts from discrete network updates (~30Hz replication). */
+	float SmoothedBodyYaw = 0.0f;
+
 	/** Original actor yaw at BeginPlay (for neutral return when TargetActor is null). */
 	float OriginalActorYaw = 0.0f;