Core & Architecture

Scene

A Scene is the space that holds every GameObject, light, and camera — each .unity file is a Scene: a level, a menu, or a distinct game state you load.

Imagine...

A Scene is like a single episode of a show. Each episode has its own set, characters, and story. When you cut to the next episode (load a Scene), the old set vanishes. Characters that survive every episode use DontDestroyOnLoad() — like the protagonist who never disappears between levels.

The concept in detail

A typical game has many Scenes: MainMenu, Level_01, Level_02, GameOver, Loading… Splitting them keeps memory in check — you only load what you need.

To switch Scenes, use the SceneManager class. LoadScene() is synchronous (blocking — the game freezes), while LoadSceneAsync() loads in the background so you can show a Loading Screen.

Additive Loading: load several Scenes at once, stacked on top of each other. Common for world streaming or splitting UI Scene from gameplay Scene.

A GameObject that must survive Scene loads uses DontDestroyOnLoad(gameObject). Always pair it with a Singleton so you do not spawn a duplicate when the Scene reloads.

Scene flow

🎬

MainMenu

index: 0

→

⏳

index: 1

→

🎮

Level_01

index: 2

→

💀

GameOver

index: 3

Single Mode

Load new Scene → unload the old one

Additive Mode

Load extra Scene → keep the old one

Hands-on steps

Create a new Scene

Menu File → New Scene to create a Scene.

Add it to Build Settings

File → Build Settings → drag the .unity file into the list. The index is the number used by LoadScene(index).

Switch Scenes from a script

Add using UnityEngine.SceneManagement; then call SceneManager.LoadScene().

Loading Screen with Async

Use a Coroutine + LoadSceneAsync(), read AsyncOperation.progress (0.0 → 0.9) to update a progress bar.

Interactive simulator

Click Load Scene to simulate a transition with a Loading Screen. Watch GameManager survive every Scene.

Build Settings

🔒 GameManager

DontDestroyOnLoad

Active Scene: MainMenu · Build Index: 0

Code example

Basic

using UnityEngine;
using UnityEngine.SceneManagement;

public class SceneBasics : MonoBehaviour
{
  void Awake()
  {
      // Keep this object across every Scene (Singleton GameManager)
      DontDestroyOnLoad(gameObject);
  }

  public void LoadLevel1()
      => SceneManager.LoadScene("Level_01");      // by name

  public void RestartCurrentScene()
  {
      int idx = SceneManager.GetActiveScene().buildIndex;
      SceneManager.LoadScene(idx);                   // by index
  }

  public void LoadNextScene()
  {
      int next = SceneManager.GetActiveScene().buildIndex + 1;
      SceneManager.LoadScene(next);
  }
}

Code example

Advanced

using System.Collections;
using UnityEngine;
using UnityEngine.SceneManagement;
using UnityEngine.UI;

public class SceneLoader : MonoBehaviour
{
  public static SceneLoader Instance { get; private set; }
  [SerializeField] private Slider progressBar;

  void Awake()
  {
      // Singleton: only one instance may exist
      if (Instance != null) { Destroy(gameObject); return; }
      Instance = this;
      DontDestroyOnLoad(gameObject);
  }

  public void LoadScene(string sceneName)
      => StartCoroutine(LoadAsync(sceneName));

  private IEnumerator LoadAsync(string sceneName)
  {
      AsyncOperation op = SceneManager.LoadSceneAsync(sceneName);
      op.allowSceneActivation = false;

      while (op.progress < 0.9f)
      {
          float progress = Mathf.Clamp01(op.progress / 0.9f);
          if (progressBar) progressBar.value = progress;
          yield return null;
      }

      if (progressBar) progressBar.value = 1f;
      yield return new WaitForSeconds(0.5f);
      op.allowSceneActivation = true;
  }
}

📌 Quick recap

▸A Scene must be in Build Settings before LoadScene can find it
▸DontDestroyOnLoad keeps an object across transitions
▸Use Async + a Coroutine to build a Loading Screen
▸Additive mode for world streaming and splitting UI

⚠️ Common mistakes

❌ Forgetting to add the Scene to Build Settings
"Scene not found in Build Settings" error
✅ File → Build Settings → Add Open Scenes
❌ DontDestroyOnLoad without a Singleton guard
Reloading the Scene creates a second GameManager
✅ if (Instance != null) Destroy(this);