Introduction to Real-Time Multiplayer Games in Unity Using Photon Networking

Overview of Multiplayer Game Development

Multiplayer games are basically harder to develop compared to single-player, because by nature, multiplayer games call for networked communication amongst devices. Any multiplayer game fundamentally will be a question of synchronization-to appropriately guarantee that all players experience the same game world at a given time, despite possibly huge latency or differences in hardware. There are various networking strategies for different genres of multiplayer games, ranging from turn-based systems to real-time action games.

Photon PUN Photon Unity Networking is one of the most popular tools when developing multiplayer games in real time in Unity. A lot of fundamental networking, including player sync as well as server and matchmaking connection, will be taken care of so the developer will be bothered with the game mechanics itself. Assembling a multiplayer game should be done systematically-from networking setup to synchronizing the player’s actions on the network.

Step-by-Step Implementation: A Minimalistic Multiplayer Game using Photon PUN

Photon PUN Setup in Unity

To begin working with Photon:

• Sign into an account and open a new project in Photon.
• Go to Photon Engine.
• First, sign up and create a new Photon project.
• Once the creation of your project, copy the App ID to be used in Unity.

Set up Unity

• Open Unity and make a new project. Take a trip to Unity Asset Store,.
• Search for Photon PUN 2 and download the package.
• This is done once the Photon PUN Wizard window opens; in the field provided enter your App ID, and your Unity project is immediately connected to Photon’s backend.

Photon is the place where developers can take advantage of cloud-based service management of multiplayer features such as matchmaking, real-time room management, and data synchronization between players.

Implementing the Multiplayer Lobby System

In a multiplayer game, usually, players join a lobby before starting or joining a game. Here’s how to make a simple multiplayer lobby with Photon:

Create UI for Lobby: Create a very minimalist interface using Unity’s Canvas system. Add an input field to type in the name of the room, and add buttons for create and join rooms. Photon Script to Connect Lobbies Here is the nasty script to connect players to the photon network, so they can either create or join rooms:.

   using Photon.Pun;
   using UnityEngine;
   using UnityEngine.UI;

   public class LobbyManager : MonoBehaviourPunCallbacks
   {
       public InputField roomNameInputField;
       public Button createRoomButton;

       void Start()
       {
           PhotonNetwork.ConnectUsingSettings(); // Connects to Photon cloud
       }

       public override void OnConnectedToMaster()
       {
           createRoomButton.interactable = true; // Enable the button once connected
       }

       public void CreateRoom()
       {
           string roomName = roomNameInputField.text;
           if (!string.IsNullOrEmpty(roomName))
           {
               PhotonNetwork.CreateRoom(roomName);
           }
       }

       public void JoinRoom()
       {
           string roomName = roomNameInputField.text;
           if (!string.IsNullOrEmpty(roomName))
           {
               PhotonNetwork.JoinRoom(roomName);
           }
       }
   }

Explaining the Script:

• PhotonNetwork.ConnectUsingSettings(): Connects the player to Photon’s cloud service.
• OnConnectedToMaster(): This is called when the player successfully connects to Photon’s master server, enabling the ability to create or join a room.
• PhotonNetwork.CreateRoom(): This function creates a room with the name provided in the input field.

3. Synchronizing Player Movement in Multiplayer Games

Once a player joins a room, you need to spawn a player prefab and synchronize its movement between all players in the room.

Creating a Player Prefab:

• Create a simple player model or a cube in Unity and attach a Rigidbody component for physics-based movement.
• Add a PhotonView component to the player prefab, which is responsible for syncing the player’s data across all clients.

Writing the Player Controller Script:

   using Photon.Pun;
   using UnityEngine;

   public class PlayerController : MonoBehaviourPunCallbacks
   {
       public float speed = 5f;

       void Update()
       {
           if (photonView.IsMine)
           {
               // Only allow the local player to move their own character
               float moveX = Input.GetAxis("Horizontal") * speed * Time.deltaTime;
               float moveZ = Input.GetAxis("Vertical") * speed * Time.deltaTime;

               transform.Translate(new Vector3(moveX, 0, moveZ));
           }
       }
   }

3. Explaining the Script:

• photonView.IsMine: This ensures only the player who owns the PhotonView can control the movement of that character, preventing multiple players from controlling the same character.
• Input.GetAxis("Horizontal") and Input.GetAxis("Vertical"): These functions detect user input to move the character.

3. Spawning the Player: In the game manager script, you need to instantiate the player prefab when the player joins a room:

   public override void OnJoinedRoom()
   {
       PhotonNetwork.Instantiate("PlayerPrefab", new Vector3(0, 0, 0), Quaternion.identity);
   }

4. Synchronizing Object States Using PhotonView and RPCs

Beyond player movement, you can synchronize other aspects of the game, such as object states (like opening doors or triggering events).

1. Remote Procedure Calls (RPCs) in Photon:

• Photon allows you to send RPCs to all connected players to trigger certain actions.

   public class ObjectInteraction : MonoBehaviourPun
   {
       [PunRPC]
       public void OpenDoor()
       {
           // Logic to open the door
       }

       void OnTriggerEnter(Collider other)
       {
           if (other.CompareTag("Player"))
           {
               photonView.RPC("OpenDoor", RpcTarget.AllBuffered);
           }
       }
   }

In the above example, on interaction of a player with an object, for example, with the door, the RPC which will open the door to everybody is opened.

Deeper issues in Multiplayer Games

Latency Compensation: In a multi-player environment, one needs to compensate for network latency especially in real-time applications. You would, therefore, apply techniques like client-side prediction (where the game estimates where a player will be) or lag compensation to ensure smoothness in gaming across different network speeds.

Matchmaking Strategies: Beyond just simple room-based multiplayer, you can do much more than that-like ELO-based rankings or skill-based matchmaking. All this is possible with the server-side capabilities of Photon.

Security and Prevention of Cheating: Always check from the server side in an online multiplayer in order to prevent any cheating. Techniques such as authoritative servers, encryption, and data validation can save the game.

Conclusion: Finally, this post gives an overview of how to create a multiplayer game in Unity using Photon Networking. We covered must-haves such as setting up Photon, creating a lobby, syncing player movement, and much more.nt, and handling object interactions. With these concepts, you’re well on your way to building a basic real-time multiplayer game.