Scene Management (SceneManager)

What is SceneManager?

SceneManager is a class in Unity for loading and managing scenes. It provides features such as game restart, scene transitions, and additive scene loading.

Basic Concepts

• Scene: One screen or level of a game
• Scene Load: Load and activate a scene
• Scene Transition: Move from current scene to another scene
• Scene Restart: Reload current scene

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1. Basic Scene Loading

LoadScene() - Load Scene

using UnityEngine;
using UnityEngine.SceneManagement;

public class GameManager : MonoBehaviour
{
    public void RestartGame()
    {
        // Reload current scene
        SceneManager.LoadScene("SampleScene");
    }
}

Load by Scene Name

using UnityEngine;
using UnityEngine.SceneManagement;

public class SceneLoader : MonoBehaviour
{
    public void LoadMainMenu()
    {
        // Switch to "MainMenu" scene
        SceneManager.LoadScene("MainMenu");
    }
    
    public void LoadGameScene()
    {
        // Switch to "GameScene" scene
        SceneManager.LoadScene("GameScene");
    }
}

Load by Scene Index

using UnityEngine;
using UnityEngine.SceneManagement;

public class SceneLoader : MonoBehaviour
{
    public void LoadSceneByIndex(int sceneIndex)
    {
        // Load by scene index (starts from 0)
        SceneManager.LoadScene(0);  // First scene
        SceneManager.LoadScene(1);  // Second scene
    }
}

---

2. Restart Current Scene

GetActiveScene() - Get Current Scene

using UnityEngine;
using UnityEngine.SceneManagement;

public class GameManager : MonoBehaviour
{
    public void RestartGame()
    {
        // Reset game over state
        isGameOver = false;
        
        // Reload with current active scene name
        SceneManager.LoadScene(
            SceneManager.GetActiveScene().name
        );
    }
}

Practical Example

using UnityEngine;
using UnityEngine.SceneManagement;
using UnityEngine.UI;

public class GameManager : MonoBehaviour
{
    public static bool isGameOver = false;
    
    [Header("UI References")]
    public Image hpGauge;
    public GameObject restartButton;
    public GameObject gameOverText;
    
    public void DecreaseHp()
    {
        hpGauge.fillAmount -= 0.2f;
        hpGauge.fillAmount = Mathf.Clamp01(hpGauge.fillAmount);
        
        if (hpGauge.fillAmount <= 0f)
        {
            isGameOver = true;
            gameOverText.SetActive(true);
            restartButton.SetActive(true);
        }
    }
    
    public void RestartGame()
    {
        // Reset game over state
        isGameOver = false;
        
        // Reload current scene
        SceneManager.LoadScene(
            SceneManager.GetActiveScene().name
        );
    }
}

---

3. Scene Loading Modes

LoadSceneMode.Single - Load Single Scene

using UnityEngine;
using UnityEngine.SceneManagement;

public class SceneLoader : MonoBehaviour
{
    void Start()
    {
        // Unload current scene and load new scene (default)
        SceneManager.LoadScene("NewScene", LoadSceneMode.Single);
    }
}

LoadSceneMode.Additive - Additive Scene Load

using UnityEngine;
using UnityEngine.SceneManagement;

public class SceneLoader : MonoBehaviour
{
    void Start()
    {
        // Keep current scene and additively load new scene
        SceneManager.LoadScene("UI", LoadSceneMode.Additive);
    }
}

---

4. Getting Scene Information

GetActiveScene() - Get Current Active Scene

using UnityEngine;
using UnityEngine.SceneManagement;

public class SceneInfo : MonoBehaviour
{
    void Start()
    {
        // Get current active scene information
        Scene currentScene = SceneManager.GetActiveScene();
        
        Debug.Log("Scene name: " + currentScene.name);
        Debug.Log("Scene index: " + currentScene.buildIndex);
        Debug.Log("Scene path: " + currentScene.path);
    }
}

GetSceneByName() - Find Scene by Name

using UnityEngine;
using UnityEngine.SceneManagement;

public class SceneFinder : MonoBehaviour
{
    void Start()
    {
        // Find scene by name
        Scene scene = SceneManager.GetSceneByName("GameScene");
        
        if (scene.IsValid())
        {
            Debug.Log("Found scene: " + scene.name);
        }
    }
}

---

5. Practical Examples

Example 1: Game Restart Button

using UnityEngine;
using UnityEngine.SceneManagement;
using UnityEngine.UI;

public class GameManager : MonoBehaviour
{
    public static bool isGameOver = false;
    
    [Header("UI References")]
    public GameObject restartButton;
    public GameObject gameOverText;
    
    public void RestartGame()
    {
        // Reset game over state
        isGameOver = false;
        
        // Reload current scene
        SceneManager.LoadScene(
            SceneManager.GetActiveScene().name
        );
    }
}

Unity Setup:

1. Create UI Button
2. Assign GameManager to Button's OnClick event
3. Select RestartGame() method

Example 2: Return to Main Menu

using UnityEngine;
using UnityEngine.SceneManagement;

public class MenuManager : MonoBehaviour
{
    public void LoadMainMenu()
    {
        // Switch to main menu scene
        SceneManager.LoadScene("MainMenu");
    }
    
    public void LoadGame()
    {
        // Switch to game scene
        SceneManager.LoadScene("GameScene");
    }
}

Example 3: Move to Next Level

using UnityEngine;
using UnityEngine.SceneManagement;

public class LevelManager : MonoBehaviour
{
    void OnTriggerEnter2D(Collider2D other)
    {
        if (other.CompareTag("Player"))
        {
            // Move to next level
            LoadNextLevel();
        }
    }
    
    void LoadNextLevel()
    {
        // Get current scene index
        int currentSceneIndex = SceneManager.GetActiveScene().buildIndex;
        
        // Move to next scene
        SceneManager.LoadScene(currentSceneIndex + 1);
    }
}

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6. Scene Build Settings

Scenes must be added to Build Settings before they can be loaded.

Adding Scenes to Build Settings

1. Open File > Build Settings
2. Click Add Open Scenes (add currently open scene)
3. Or drag and drop scenes
4. Adjust scene order (index starts from 0)

Checking Scene Name

using UnityEngine;
using UnityEngine.SceneManagement;

public class SceneChecker : MonoBehaviour
{
    void Start()
    {
        // Check current scene name
        string sceneName = SceneManager.GetActiveScene().name;
        Debug.Log("Current scene: " + sceneName);
    }
}

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7. Precautions

1. Enter Scene Name Accurately

// ❌ Problem: Error if scene name is not exact
SceneManager.LoadScene("Game");  // Error if actual name is "GameScene"

// ✅ Solution: Use exact scene name
SceneManager.LoadScene("GameScene");

2. Add Scene to Build Settings

// Scenes not added to Build Settings cannot be loaded
// Need to add scene in File > Build Settings

3. Objects Destroyed on Scene Transition

// Using LoadSceneMode.Single destroys all objects in current scene
// Use DontDestroyOnLoad() for objects to keep

4. Async Loading

// Recommended to use async loading for large scenes
// Use SceneManager.LoadSceneAsync()

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8. Summary

Key SceneManager Functions

Function	Purpose	Example
LoadScene(name)	Load scene	LoadScene("GameScene")
LoadScene(index)	Load scene by index	LoadScene(0)
GetActiveScene()	Get current scene	GetActiveScene().name
GetSceneByName(name)	Find scene by name	GetSceneByName("Game")

Scene Loading Modes

• LoadSceneMode.Single: Unload current scene and load new scene
• LoadSceneMode.Additive: Keep current scene and additively load new scene

Best Practices

1. Constant scene names: Manage scene names as constants
2. Check Build Settings: Verify scenes are added
3. Async loading: Use LoadSceneAsync() for large scenes
4. Scene transition effects: Add fade in/out effects

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Practice Problems

1. Create a button that restarts the current scene when the game is over.

2. Create a button that transitions from main menu to game scene.

3. Create a system that automatically moves to the next level.

4. Create a class that manages scene names as constants.