Hello! In this article, we will cover the basics of creating a multiplayer game using Unity and explore player synchronization and character behavior synchronization in depth. Synchronizing the movements and actions of each player in a multiplayer game is a very important element, and implementing it correctly can enhance the quality of the game and the player’s experience.

1. Unity and Multiplayer Games

Unity provides a platform for easily developing various multiplayer games. By using network features, multiple players can connect and interact with each other in the same game world. However, one of the biggest challenges of multiplayer games is state synchronization between clients. The movements and actions of each player must be accurately synchronized between the server and clients to provide a seamless gaming experience.

2. Basic Concepts of Player Synchronization

Player synchronization is the process of ensuring that player objects from different clients in the network maintain the same state. To achieve this, we need to understand the following two key concepts:

  • State Synchronization: The process of synchronizing the player’s position, rotation, animation state, etc., with other clients and the server.
  • Action Synchronization: The process of passing the player’s actions or inputs to other clients and reflecting them.

3. Synchronizing Player Character Behavior

Now, let’s learn how to synchronize the behavior of player characters. To do this, we can use network libraries such as UNet or Mirror to perform the synchronization.

3.1 Player Synchronization Using UNet

Unity’s UNet is a tool that allows for easy construction of multiplayer network games. Let’s write a basic script to synchronize the movements of players using UNet.

using UnityEngine;
    using UnityEngine.Networking;

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

        void Update()
        {
            if (!isLocalPlayer) return;

            float moveHorizontal = Input.GetAxis("Horizontal");
            float moveVertical = Input.GetAxis("Vertical");

            Vector3 movement = new Vector3(moveHorizontal, 0.0f, moveVertical);
            transform.Translate(movement * speed * Time.deltaTime);
        }

        [ClientRpc]
        void RpcUpdatePosition(Vector3 newPosition)
        {
            transform.position = newPosition;
        }
    }

The code above provides the functionality for each client to receive player input and move that player. The isLocalPlayer property checks if the client is controlling its own player character and updates its position based on its inputs. Then, the RpcUpdatePosition method is used to request a position update from the server.

3.2 Player Synchronization Using Mirror

Mirror is a successor project to UNet that offers more advanced features. Let’s take a look at how to synchronize the behavior of player characters using Mirror.

using UnityEngine;
    using Mirror;

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

        void Update()
        {
            if (!isLocalPlayer) return;

            float moveHorizontal = Input.GetAxis("Horizontal");
            float moveVertical = Input.GetAxis("Vertical");

            Vector3 movement = new Vector3(moveHorizontal, 0.0f, moveVertical);
            transform.Translate(movement * speed * Time.deltaTime);
            CmdUpdatePosition(transform.position);
        }

        [Command]
        void CmdUpdatePosition(Vector3 newPosition)
        {
            RpcUpdatePosition(newPosition);
        }

        [ClientRpc]
        void RpcUpdatePosition(Vector3 newPosition)
        {
            transform.position = newPosition;
        }
    }

In the case of Mirror, the Command and ClientRpc attributes are used to manage communication between the client and server. The client receives input, sends the new position to the server, and the server reflects this to all clients.

4. Synchronization Optimization

When performing synchronization, optimization is an important factor. Synchronizing the positions and states of all players every frame can negatively impact network performance. Therefore, the following optimization methods can be considered:

  • Sampling and Interval Adjustment: Set up clients to send synchronization requests only at specific intervals.
  • Prediction and Correction: Process movements based on predicted positions on the client side and correct them if they do not match server data.
  • Zone-Based Synchronization: Configure synchronization to occur only when players are within a specific area, reducing network traffic.

5. Conclusion

In this tutorial, we explored player synchronization and character behavior synchronization in multiplayer games using Unity. We provided basic implementation examples of how to synchronize the behavior of player characters using UNet and Mirror. Developing multiplayer games comes with many challenges, but understanding the right methods and patterns can take you one step closer to creating great games. Keep practicing and implementing various features to enjoy the charm of multiplayer gaming!