Scene management

Adding new scenes

• Scenes are the different levels or screens of your game
• You can add new scenes to your game with File > New scene
• Then save it to your Scenes folder with File > Save scene
• You can open another scenes from the Project window
• Note: If you open a previously-made Unity project the first time, Unity won't open any scenes, you have to do them manually from the Project window!

Building a game with multiple scenes

• When you have multiple scenes, you need to add them to your build settings so you're including them in the game
  • File > Build Settings > Scenes in Build
  • Either drag-and-drop your scenes here or click Add Open Scenes
  • The top-most scene will be the one that gets loaded when the game starts
• See Building for more about Build settings.

Scene manager

• Script Reference: SceneManager
• Scene Manager, uh, manages scenes
• To use it, you need to import SceneManagement:

  using UnityEngine.SceneManagement;
  

Loading a scene

• To move between scenes, use SceneManager.LoadScene

  SceneManager.LoadScene(sceneBuildIndex);
  SceneManager.LoadScene(sceneName);
  

• This unloads your current scene and loads the one you specified
• Loading the scene you are currently in resets the scene (but not static variables!)
• To get information about your current scene, use SceneManager.GetActiveScene():

  if (SceneManager.GetActiveScene().name == "GameOver")
  {
      // do stuff
  } 
  

Loading complex scenes

• To load a scene without unloading your current scene, use LoadSceneMode.Additive

  SceneManager.LoadScene("YourScene", LoadSceneMode.Additive);
  

  • Useful for big open worlds and interconnected areas
  • If you use it, you might need to unload previously loaded levels as well
  • Script Reference: SceneManager.UnloadSceneAsync

Data persistence between scenes

• Learn: Data persistence between scenes
• By default, no values persist when moving from a scene to another
• You can change this by calling DontDestroyOnLoad and giving the gameObject you want to persist as an argument

  private void Awake()
  {
      DontDestroyOnLoad(gameObject);
  }
  

  • Note: this only works for root GameObjects - not for children!

Creating a data manager

• We can create a data manager for bookkeeping score etc.
  • LevelManager, GameManager, UIManager, etc...
• We create a static variable that refers to it (here named instance)
  • we can use it easily from anywhere

    public class ScoreManager : MonoBehaviour
    {
        public static ScoreManager instance;
    
        private void Awake()
        {
            instance = this;
            DontDestroyOnLoad(gameObject);
        }
    }
    

    ScoreManager.instance.AddScore(1);
    

Prevent other instances of data manager from appearing

• To make sure you only have one ScoreManager at all times, add these lines to the top of your ScoreManager's Awake method.

  if (instance != null)
  {
      Destroy(gameObject);
      return;
  }
  

• This is commonly known in software development as the singleton pattern.

Closing the game

• Call Application.Quit(); when you want to close the game
  • (Don't worry, this does not close the Unity editor)

Extra: Do stuff when scene is loaded

Script Reference: SceneManager.sceneLoaded

// called first
void OnEnable()
{
    Debug.Log("OnEnable called");
    SceneManager.sceneLoaded += OnSceneLoaded;
}

// called second
void OnSceneLoaded(Scene scene, LoadSceneMode mode)
{
    Debug.Log("OnSceneLoaded: " + scene.name);
    Debug.Log(mode);
}

Extra: Listing multiple scenes

• Usable for a Level select screen, etc
• Get a list of files in a given path:

  string [] files = System.IO.Directory.GetFiles(path);
  foreach (string file in files)
  {
      //Do work on the files here
  }
  

• Then, choose ones that .EndsWith(".unity")
• Hint: Application.datapath tells the root of Assets path

Extra: Resources

• Script Reference: Resources
• Script Reference: Resources.LoadAll
  • Loads all assets in a folder or file at path in a Resources folder.