Optimizing Montage Performance for Multiplayer

In this lesson, you will learn how to trigger Animation Montages in a multiplayer environment so that every player sees the same animation exactly when it happens.

In a multiplayer game, you cannot simply call Play Montage from a local client controller. If you do, the animation will trigger on your machine, but the server and other players will remain oblivious, leading to a "ghost" animation that only you can see. To keep your world synchronized, you must use RPCs (Remote Procedure Calls) to bridge the gap between the client and the server.

The Server-Authoritative Workflow

The golden rule of network-ready montages is: The client tells the server to play the animation, and the server tells everyone else to play it.

1. Client Request: When an action occurs (like pressing "Fire"), the local client sends a Server RPC to the server.
2. Server Execution: The server validates the request and then calls a Multicast RPC (or uses a RepNotify) to tell all connected clients to play the specific UAnimMontage asset.

Because the PlayMontage node inside a character’s AnimInstance is automatically replicated when called on the server, you often don't need a custom multicast if you trigger it directly from a server-side event.

Implementation Pattern

Here is the standard flow for triggering a replicated attack:

// 1. Triggered by Input (Client-side)
void AMyCharacter::PerformAttack() {
    Server_PlayAttackMontage();
}

// 2. Server ensures the state is replicated
void AMyCharacter::Server_PlayAttackMontage_Implementation() {
    if (AttackMontage) {
        // Calling this on the server replicates the montage to all clients
        PlayAnimMontage(AttackMontage);
    }
}

By routing the montage through the server, you ensure that the AnimInstance state remains synchronized across the network. If a player joins the game halfway through an animation, the server’s authority ensures that their machine receives the necessary data to play the montage at the correct playback position, preventing desyncs. Always remember that animations are purely visual; keep your gameplay logic (like damage calculation) tied to server-side checks, not just the animation timing itself.

Key Takeaway: To synchronize montages in multiplayer, trigger the animation on the server so that the replication system propagates the playback state to all connected clients automatically.