Multiserver Shooter Tutorial

2: Replicate health changes

Step 1: Make the change

In this project each TPSCharacter contains a variable called CurrentHealth, which keeps track of that character’s health. On your servers, CurrentHealth is reduced whenever a character is shot, but this reduction is not replicated on the clients connected to the game. This is because the CurrentHealth variable is not setup for replication.

To resolve this you need to mark the CurrentHealth property for replication, just as you would in the native Unreal Actor replication workflow. To do this:

  1. In your IDE, open UnrealGDKThirdPersonShooter\Game\Source\ThirdPersonShooter\Characters\TPSCharacter.h.
  2. Navigate to the declaration of the CurrentHealth variable, and add the UProperty specifiers ReplicatedUsing = OnRep_CurrentHealth. The UProperty should now look like this:

    UPROPERTY(ReplicatedUsing = OnRep_CurrentHealth)
    int32 CurrentHealth; 

    You have now marked this property for replication using the OnRep_CurrentHealth function that you’ll implement in the next section.

    Next you need to update the GetLifetimeReplicatedProps implementation of the TPSCharacter to specify the replication conditions for the CurrentHealth variable:

  3. In your IDE, open UnrealGDKThirdPersonShooter\Game\Source\ThirdPersonShooter\Characters\TPSCharacter.cpp.

  4. Navigate to the GetLifetimeReplicatedProps function (which is implementd around line 182), and insert the following snippet:

    // Only replicate health to the owning client.
    DOREPLIFETIME_CONDITION(ATPSCharacter, CurrentHealth, COND_OwnerOnly);

    Note: You only want to replicate the CurrentHealth variable to the client that owns this Actor, thus you specify the COND_OwnerOnly flag.

    Finally, you need to implement the OnRep_CurrentHealth function so that the player health UI gets updated when the CurrentHealth variable is replicated:

  5. In your IDE, open UnrealGDKThirdPersonShooter\Game\Source\ThirdPersonShooter\Characters\TPSCharacter.h.

  6. In the public scope of the class, insert the following snippet:

        void OnRep_CurrentHealth();
  7. In your IDE, open UnrealGDKThirdPersonShooter\Game\Source\ThirdPersonShooter\Characters\TPSCharacter.cpp and insert the following snippet:

    void ATPSCharacter::OnRep_CurrentHealth()
        if (GetNetMode() != NM_DedicatedServer)
        ATPSPlayerController* PC = Cast<ATPSPlayerController>(GetController());
            if (PC)
                PC->UpdateHealthUI(CurrentHealth, MaxHealth);
                UE_LOG(LogTPS, Warning, TEXT("Couldn't find a player controller for character: %s"), *this->GetName());

Notice that the workflow you just used mirrors that of native Unreal.

Step 2: Rebuild your project

Because you have changed code in a function, you now need to rebuild your project. Additionally, because you’ve modified code related to replication, you need to generate schema. To do this:

  1. Open ThirdPersonShooter.sln with Visual Studio.
  2. In the Solution Explorer window, right-click on ThirdPersonShooter and select Build.
  3. Open ThirdPersonShooter.uproject in the Unreal Editor and click Schema and then Snapshot.

Now let’s test our health replication in another local deployment.

> Next: 3: Test changes locally

2019-04-30 Page updated with limited editorial review

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