Unity3D 进阶教程 - 16 Netcode for GameObjects

概述

Netcode for GameObjects 是 Unity 官方推出的多人游戏网络库，取代了旧版的 UNET（已废弃）。它基于 客户端-服务器（Client-Server）模型——一个权威服务器处理所有关键逻辑，客户端负责输入和渲染。

本篇覆盖 Netcode 的核心概念：NetworkObject、NetworkVariable、RPC、客户端-服务器同步、玩家权限控制。

1. 核心概念

1.1 客户端-服务器模型

服务器（权威）：
  ├── 验证玩家输入
  ├── 更新游戏状态
  ├── 同步到所有客户端
  └── 处理延迟补偿

客户端（非权威）：
  ├── 收集玩家输入
  ├── 发送给服务器
  ├── 接收服务器状态
  └── 渲染画面

1.2 安装

Package Manager -> Unity Registry -> Netcode for GameObjects

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2. NetworkObject 与 NetworkVariable

2.1 NetworkObject

任何需要网络同步的 GameObject 必须附加 NetworkObject 组件：

using Unity.Netcode;

public class Bullet : NetworkBehaviour
{
    [ServerRpc]
    private void SpawnBulletServerRpc(Vector3 origin, Vector3 direction)
    {
        var bullet = Instantiate(bulletPrefab, origin, Quaternion.LookRotation(direction));
        bullet.GetComponent<NetworkObject>().Spawn();
    }
}

2.2 NetworkVariable

自动同步的状态变量：

public class PlayerHealth : NetworkBehaviour
{
    public NetworkVariable<int> Health = new(100,
        NetworkVariableReadPermission.Everyone,
        NetworkVariableWritePermission.Server);

    public NetworkVariable<bool> IsDead = new(false,
        NetworkVariableReadPermission.Everyone,
        NetworkVariableWritePermission.Server);

    private void Awake()
    {
        Health.OnValueChanged += OnHealthChanged;
    }

    private void OnHealthChanged(int oldValue, int newValue)
    {
        UpdateHealthUI(newValue);
    }

    [ServerRpc]
    public void TakeDamageServerRpc(int damage)
    {
        if (IsDead.Value) return;
        Health.Value -= damage;
        if (Health.Value <= 0)
        {
            Health.Value = 0;
            IsDead.Value = true;
        }
    }
}

---

3. RPC 调用

3.1 ServerRpc（客户端 -> 服务器）

public class PlayerController : NetworkBehaviour
{
    [ServerRpc]
    private void SubmitInputServerRpc(Vector3 movement, bool jump)
    {
        transform.position += movement * Time.deltaTime * _moveSpeed;
    }

    private void Update()
    {
        if (!IsOwner) return;
        var move = new Vector3(Input.GetAxis("Horizontal"), 0, Input.GetAxis("Vertical"));
        if (move != Vector3.zero)
            SubmitInputServerRpc(move, Input.GetButtonDown("Jump"));
    }
}

3.2 ClientRpc（服务器 -> 客户端）

public class GameManager : NetworkBehaviour
{
    [ClientRpc]
    private void ShowExplosionClientRpc(Vector3 position, float radius)
    {
        Instantiate(_explosionPrefab, position, Quaternion.identity);
    }

    [ClientRpc(RequireOwnership = false)]
    private void UpdateScoreClientRpc(int playerId, int newScore)
    {
        ScoreUI.Instance.UpdatePlayerScore(playerId, newScore);
    }
}

---

4. 玩家管理

public class GameManager : NetworkBehaviour
{
    [SerializeField] private GameObject _playerPrefab;

    public override void OnNetworkSpawn()
    {
        NetworkManager.Singleton.OnClientConnectedCallback += OnPlayerConnected;
        NetworkManager.Singleton.OnClientDisconnectCallback += OnPlayerDisconnected;
    }

    private void OnPlayerConnected(ulong clientId)
    {
        if (!IsServer) return;

        var spawnPos = new Vector3(Random.Range(-10f, 10f), 0, Random.Range(-10f, 10f));
        var player = Instantiate(_playerPrefab, spawnPos, Quaternion.identity);
        var networkPlayer = player.GetComponent<NetworkObject>();
        networkPlayer.SpawnAsPlayerObject(clientId);
    }

    private void OnPlayerDisconnected(ulong clientId)
    {
        if (!IsServer) return;

        if (NetworkManager.Singleton.ConnectedClients.TryGetValue(clientId, out var client))
        {
            client.PlayerObject?.Despawn();
        }
    }
}

---

5. 网络位置同步

public class NetworkTransform : NetworkBehaviour
{
    private NetworkVariable<Vector3> _networkPosition = new();
    [SerializeField] private float _lerpSpeed = 10f;

    private void Update()
    {
        if (IsOwner)
        {
            if (IsServer)
                _networkPosition.Value = transform.position;
        }
        else
        {
            transform.position = Vector3.Lerp(
                transform.position, _networkPosition.Value, Time.deltaTime * _lerpSpeed);
        }
    }
}

---

6. 测试与调试

public class NetworkTester : MonoBehaviour
{
    private void OnGUI()
    {
        if (!NetworkManager.Singleton.IsClient && !NetworkManager.Singleton.IsServer)
        {
            if (GUILayout.Button("Host (Server + Client)"))
                NetworkManager.Singleton.StartHost();

            if (GUILayout.Button("Client"))
                NetworkManager.Singleton.StartClient();
        }
    }
}

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总结

• NetworkBehaviour 替代 MonoBehaviour，启用网络功能
• NetworkVariable 自动同步状态，服务器写入、客户端读取
• ServerRpc 客户端到服务器，ClientRpc 服务器到客户端
• NetworkObject.Spawn() 在服务器上生成网络对象
• 位置同步需要插值处理，减少网络延迟影响

下一篇将搭建 多人游戏架构实战，包括房间系统、同步策略和网络性能优化。