Converting a Single-Player Game to Mirror

This document describes steps to converting a single player game to a multiplayer game, using Mirror. The process described here is a simplified, higher level version of the actual process for a real game; it doesn’t always work exactly like this, but it provides a basic recipe for the process.

NetworkManager set-up

  • Add a new GameObject and rename it “NetworkManager”.
  • Add the NetworkManager component to the “NetworkManager” GameObject.
  • Add the NetworkManagerHUD component to the GameObject. This provides the default UI​ for managing the network game state.

See Using the NetworkManager.

Player Prefab Setup

  • Find the Prefab for the player GameObject in the game, or create a Prefab from the player GameObject
  • Add the NetworkIdentity component to the player Prefab
  • Check the LocalPlayerAuthority box on the NetworkIdentity
  • Set the playerPrefab in the NetworkManager’s Spawn Info section to the player Prefab
  • Remove the player GameObject instance from the Scene if it exists in the Scene

See Player Objects for more information.

Player Movement

  • Add a NetworkTransform component to the player Prefab
  • Update input and control scripts to respect isLocalPlayer
  • Fix Camera to use spawned player and isLocalPlayer

For example, this script only processes input for the local player:

using UnityEngine;
using Mirror;

public class Controls : NetworkBehaviour
{
    void Update()
    {
        if (!isLocalPlayer)
        {
            // exit from update if this is not the local player
            return;
        }

        // handle player input for movement
    }
}

Basic Player Game State

  • Make scripts that contain important data into NetworkBehaviours instead of MonoBehaviours
  • Make important member variables into SyncVars

See State Synchronization.

Networked Actions

  • Make scripts that perform important actions into NetworkBehaviours instead of MonoBehaviours
  • Update functions that perform important player actions to be commands

See Networked Actions.

Non-player GameObjects

Fix non-player prefabs such as enemies:

  • Add the NetworkIdentify component
  • Add the NetworkTransform component
  • Register spawnable Prefabs with the NetworkManager
  • Update scripts with game state and actions

Spawners

  • Potentially change spawner scripts to be NetworkBehaviours
  • Modify spawners to only run on the server (use isServer property or the OnStartServer() function)
  • Call NetworkServer.Spawn() for created GameObjects

Spawn Positions for Players

  • Add a new GameObject and place it at player’s start location
  • Add the NetworkStartPosition component to the new GameObject

Lobby

  • Create Lobby Scene
  • Add a new GameObject to the Scene and rename it to “NetworkLobbyManager”.
  • Add the NetworkLobbyManager component to the new GameObject.
  • Configure the Manager:
    • Scenes
    • Prefabs
    • Spawners