Keep cars and skid-steer vehicles that fall out of the world

Unreal/Plugins/AirSim/Source/Vehicles/Car/CarPawn.cpp

@@ -240,9 +240,34 @@ void ACarPawn::EndPlay(const EEndPlayReason::Type EndPlayReason)
     Super::EndPlay(EndPlayReason);
 }
 
+void ACarPawn::FellOutOfWorld(const UDamageType& dmgType)
+{
+    // The engine destroys actors that drop below the level's KillZ, but AirSim keeps using its
+    // vehicle pawns and crashes on a destroyed one. Keep the vehicle and put it back at its start
+    // pose on the next tick: this is called from the physics sync, which overrides a teleport here.
+    if (!fell_out_of_world_) {
+        UE_LOG(LogTemp, Warning, TEXT("%s fell out of the world; moving it back to its start pose"), *GetName());
+        UAirBlueprintLib::LogMessage(GetName(), TEXT("fell out of the world and was moved back to its start pose"), LogDebugLevel::Failure);
+    }
+    fell_out_of_world_ = true;
+}
+
+void ACarPawn::respawnIfFellOutOfWorld()
+{
+    if (!fell_out_of_world_)
+        return;
+    fell_out_of_world_ = false;
+    for (UPrimitiveComponent* phys_comp : UAirBlueprintLib::getPhysicsComponents(this)) {
+        phys_comp->SetPhysicsLinearVelocity(FVector::ZeroVector);
+        phys_comp->SetPhysicsAngularVelocityInDegrees(FVector::ZeroVector);
+    }
+    SetActorTransform(start_transform_, false, nullptr, ETeleportType::TeleportPhysics);
+}
+
 void ACarPawn::Tick(float Delta)
 {
     Super::Tick(Delta);
+    respawnIfFellOutOfWorld();
 
     // update physics material
     updatePhysicsMaterial();
@@ -264,6 +289,7 @@ void ACarPawn::Tick(float Delta)
 void ACarPawn::BeginPlay()
 {
     Super::BeginPlay();
+    start_transform_ = GetActorTransform();
 
     // Start an engine sound playing
     engine_sound_audio_->Play();

Unreal/Plugins/AirSim/Source/Vehicles/Car/CarPawn.h

@@ -37,6 +37,7 @@ class ACarPawn : public AWheeledVehiclePawn
     virtual void BeginPlay() override;
     virtual void Tick(float Delta) override;
     virtual void EndPlay(const EEndPlayReason::Type EndPlayReason) override;
+    virtual void FellOutOfWorld(const class UDamageType& dmgType) override;
     virtual void NotifyHit(class UPrimitiveComponent* MyComp, class AActor* Other, class UPrimitiveComponent* OtherComp, bool bSelfMoved, FVector HitLocation,
                            FVector HitNormal, FVector NormalImpulse, const FHitResult& Hit) override;
 
@@ -53,6 +54,11 @@ class ACarPawn : public AWheeledVehiclePawn
         return keyboard_controls_;
     }
 
+private:
+    void respawnIfFellOutOfWorld();
+    FTransform start_transform_;
+    bool fell_out_of_world_ = false;
+
 private:
     void updateHUDStrings();
     void setupVehicleMovementComponent();

Unreal/Plugins/AirSim/Source/Vehicles/SkidSteer/SkidVehiclePawn.cpp

@@ -244,9 +244,34 @@ void ASkidVehiclePawn::EndPlay(const EEndPlayReason::Type EndPlayReason)
 	Super::EndPlay(EndPlayReason);
 }
 
+void ASkidVehiclePawn::FellOutOfWorld(const UDamageType& dmgType)
+{
+	// The engine destroys actors that drop below the level's KillZ, but AirSim keeps using its
+	// vehicle pawns and crashes on a destroyed one. Keep the vehicle and put it back at its start
+	// pose on the next tick: this is called from the physics sync, which overrides a teleport here.
+	if (!fell_out_of_world_) {
+		UE_LOG(LogTemp, Warning, TEXT("%s fell out of the world; moving it back to its start pose"), *GetName());
+		UAirBlueprintLib::LogMessage(GetName(), TEXT("fell out of the world and was moved back to its start pose"), LogDebugLevel::Failure);
+	}
+	fell_out_of_world_ = true;
+}
+
+void ASkidVehiclePawn::respawnIfFellOutOfWorld()
+{
+	if (!fell_out_of_world_)
+		return;
+	fell_out_of_world_ = false;
+	for (UPrimitiveComponent* phys_comp : UAirBlueprintLib::getPhysicsComponents(this)) {
+		phys_comp->SetPhysicsLinearVelocity(FVector::ZeroVector);
+		phys_comp->SetPhysicsAngularVelocityInDegrees(FVector::ZeroVector);
+	}
+	SetActorTransform(start_transform_, false, nullptr, ETeleportType::TeleportPhysics);
+}
+
 void ASkidVehiclePawn::Tick(float Delta)
 {
 	Super::Tick(Delta);
+	respawnIfFellOutOfWorld();
 
 	USkeletalMeshComponent* mesh = CastChecked<USkeletalMeshComponent>(getVehicleMesh());
 	if (mesh->GetPhysicsAngularVelocityInDegrees().Size() > max_angular_velocity_)
@@ -274,6 +299,7 @@ void ASkidVehiclePawn::Tick(float Delta)
 void ASkidVehiclePawn::BeginPlay()
 {
 	Super::BeginPlay();
+	start_transform_ = GetActorTransform();
 
 	// Start an engine sound playing
 	engine_sound_audio_->Play();

Unreal/Plugins/AirSim/Source/Vehicles/SkidSteer/SkidVehiclePawn.h

@@ -37,6 +37,7 @@ class ASkidVehiclePawn : public AWheeledVehiclePawn
     virtual void BeginPlay() override;
     virtual void Tick(float Delta) override;
     virtual void EndPlay(const EEndPlayReason::Type EndPlayReason) override;
+    virtual void FellOutOfWorld(const class UDamageType& dmgType) override;
     virtual void NotifyHit(class UPrimitiveComponent* MyComp, class AActor* Other, class UPrimitiveComponent* OtherComp, bool bSelfMoved, FVector HitLocation,
         FVector HitNormal, FVector NormalImpulse, const FHitResult& Hit) override;
 
@@ -64,6 +65,11 @@ class ASkidVehiclePawn : public AWheeledVehiclePawn
     UPROPERTY(BlueprintReadWrite, EditAnywhere, Category = "SkidVehicle|General")
     bool stop_turn_ = false;
 
+private:
+    void respawnIfFellOutOfWorld();
+    FTransform start_transform_;
+    bool fell_out_of_world_ = false;
+
 private:
     void updateHUDStrings();
     void setupVehicleMovementComponent();