From be89a2840e372d72c5b978acb69a875c4598ba6b Mon Sep 17 00:00:00 2001
From: Steve Streeting <steve@stevestreeting.com>
Date: Mon, 13 Nov 2023 10:59:41 +0000
Subject: [PATCH] Add replicated physics actor

---
 ReadMe.md                                     |  1 +
 .../Private/StevesReplicatedPhysicsActor.cpp  | 51 +++++++++++++++++++
 .../Public/StevesReplicatedPhysicsActor.h     | 23 +++++++++
 3 files changed, 75 insertions(+)
 create mode 100644 Source/StevesUEHelpers/Private/StevesReplicatedPhysicsActor.cpp
 create mode 100644 Source/StevesUEHelpers/Public/StevesReplicatedPhysicsActor.h

diff --git a/ReadMe.md b/ReadMe.md
index f22b4c0..93318fd 100644
--- a/ReadMe.md
+++ b/ReadMe.md
@@ -12,6 +12,7 @@ which makes a bunch of things better:
 * [Debug visualisation](https://www.stevestreeting.com/2021/09/14/ue4-editor-visualisation-helper/)
 * [Better DataTable Row References](https://www.stevestreeting.com/2023/10/06/a-better-unreal-datatable-row-picker/)
 * [Light Flicker](doc/LightFlicker.md)
+* [Replicated Physics Actor](Source/StevesUEHelpers/Public/StevesReplicatedPhysicsActor.h)
 * Halton Sequence based random stream
 
 ## Examples
diff --git a/Source/StevesUEHelpers/Private/StevesReplicatedPhysicsActor.cpp b/Source/StevesUEHelpers/Private/StevesReplicatedPhysicsActor.cpp
new file mode 100644
index 0000000..2b6c816
--- /dev/null
+++ b/Source/StevesUEHelpers/Private/StevesReplicatedPhysicsActor.cpp
@@ -0,0 +1,51 @@
+// Copyright Steve Streeting
+// Licensed under the MIT License (see License.txt)
+#include "StevesReplicatedPhysicsActor.h"
+
+
+AStevesReplicatedPhysicsActor::AStevesReplicatedPhysicsActor()
+{
+	PrimaryActorTick.bCanEverTick = false;
+
+	bReplicates = true;
+	bStaticMeshReplicateMovement = true;
+
+	const auto MeshComp = GetStaticMeshComponent();
+	MeshComp->SetMobility(EComponentMobility::Movable);
+	MeshComp->SetCollisionObjectType(ECC_WorldDynamic);
+	MeshComp->bReplicatePhysicsToAutonomousProxy = true;
+
+	// We do NOT replicate MeshComp itself! That's expensive and unnecessary
+
+}
+
+void AStevesReplicatedPhysicsActor::BeginPlay()
+{
+	SetReplicateMovement(true);
+
+	const auto MeshComp = GetStaticMeshComponent();
+
+	// Server test, includes dedicated and listen servers
+	if (IsServer())
+	{
+		// Server collision. Block all but allow pawns through
+		// Subclasses can change this if they like you can change t
+		MeshComp->SetCollisionResponseToAllChannels(ECR_Block);
+		MeshComp->SetCollisionResponseToChannel(ECC_Pawn, ECR_Overlap);
+		MeshComp->SetSimulatePhysics(true);
+	}
+	else
+	{
+		// Ignore all collisions on client
+		MeshComp->SetCollisionResponseToAllChannels(ECR_Ignore);
+	}
+	
+	Super::BeginPlay();	
+}
+
+bool AStevesReplicatedPhysicsActor::IsServer() const
+{
+	// Server test, includes dedicated and listen servers
+	// I prefer this to Authority test because you can't replicate objects client->server or client->client anyway
+	return GetWorld()->GetNetMode() < NM_Client;
+}
diff --git a/Source/StevesUEHelpers/Public/StevesReplicatedPhysicsActor.h b/Source/StevesUEHelpers/Public/StevesReplicatedPhysicsActor.h
new file mode 100644
index 0000000..e068c6f
--- /dev/null
+++ b/Source/StevesUEHelpers/Public/StevesReplicatedPhysicsActor.h
@@ -0,0 +1,23 @@
+// Copyright Steve Streeting
+// Licensed under the MIT License (see License.txt)
+#pragma once
+
+#include "CoreMinimal.h"
+#include "Engine/StaticMeshActor.h"
+#include "StevesReplicatedPhysicsActor.generated.h"
+
+/// A static mesh actor which is simulated on the server and replicated to clients.
+/// The results will be pretty smooth on the clients due to a very specific set of settings.
+/// You MUST spawn this actor ONLY on the server!
+UCLASS(Blueprintable)
+class STEVESUEHELPERS_API AStevesReplicatedPhysicsActor : public AStaticMeshActor
+{
+	GENERATED_BODY()
+
+public:
+	AStevesReplicatedPhysicsActor();
+
+protected:
+	virtual void BeginPlay() override;
+	bool IsServer() const;
+};