Scene loading and unloading in Unity - Mini Project: Build & Apply

Scene loading and unloading

📖 Scenario: You are making a simple Unity game where the player can move between two scenes: a Main Menu and a Game Level. You want to load and unload these scenes properly to save memory and keep the game smooth.

🎯 Goal: Build a Unity script that loads the MainMenu scene first, then loads the GameLevel scene additively when a button is pressed, and unloads the MainMenu scene to switch smoothly between scenes.

📋 What You'll Learn

Create a script to manage scene loading and unloading

Load the MainMenu scene at start

Additively load the GameLevel scene on command

Unload the MainMenu scene after loading GameLevel

Use UnityEngine.SceneManagement namespace

💡 Why This Matters

🌍 Real World

Games often have multiple scenes like menus, levels, and settings. Loading and unloading scenes properly helps keep the game fast and uses less memory.

💼 Career

Understanding scene management is essential for Unity developers working on games or interactive applications to create smooth user experiences.

1

Setup initial scene loading

Write a Unity C# script called SceneController. Inside the Start() method, first call DontDestroyOnLoad(gameObject); to make this SceneController persist across scene changes, then load the scene named MainMenu using SceneManager.LoadScene with LoadSceneMode.Single.

Unity

using UnityEngine;
using UnityEngine.SceneManagement;

public class SceneController : MonoBehaviour
{
    void Start()
    {
        // Load the MainMenu scene here
    }
}

Hint

Use DontDestroyOnLoad(gameObject); first to persist the controller across scenes, then SceneManager.LoadScene with the scene name "MainMenu" and LoadSceneMode.Single to load the scene alone.

2

Add a method to load the GameLevel scene additively

Add a public method called LoadGameLevel() to the SceneController class. Inside it, load the scene named GameLevel using SceneManager.LoadScene with LoadSceneMode.Additive.

Unity

using UnityEngine;
using UnityEngine.SceneManagement;

public class SceneController : MonoBehaviour
{
    void Start()
    {
        DontDestroyOnLoad(gameObject);
        SceneManager.LoadScene("MainMenu", LoadSceneMode.Single);
    }

    // Add LoadGameLevel method here
}

Hint

Create a public method LoadGameLevel() and inside it call SceneManager.LoadScene with "GameLevel" and LoadSceneMode.Additive.

3

Add a method to unload the MainMenu scene

Add a public method called UnloadMainMenu() to the SceneController class. Inside it, unload the scene named MainMenu using SceneManager.UnloadSceneAsync.

Unity

using UnityEngine;
using UnityEngine.SceneManagement;

public class SceneController : MonoBehaviour
{
    void Start()
    {
        DontDestroyOnLoad(gameObject);
        SceneManager.LoadScene("MainMenu", LoadSceneMode.Single);
    }

    public void LoadGameLevel()
    {
        SceneManager.LoadScene("GameLevel", LoadSceneMode.Additive);
    }

    // Add UnloadMainMenu method here
}

Hint

Create a public method UnloadMainMenu() and inside it call SceneManager.UnloadSceneAsync with "MainMenu".

4

Print confirmation after loading and unloading scenes

Add Debug.Log statements inside LoadGameLevel() and UnloadMainMenu() methods to print "GameLevel scene loaded" and "MainMenu scene unloaded" respectively.

Unity

using UnityEngine;
using UnityEngine.SceneManagement;

public class SceneController : MonoBehaviour
{
    void Start()
    {
        DontDestroyOnLoad(gameObject);
        SceneManager.LoadScene("MainMenu", LoadSceneMode.Single);
    }

    public void LoadGameLevel()
    {
        SceneManager.LoadScene("GameLevel", LoadSceneMode.Additive);
        // Add Debug.Log here
    }

    public void UnloadMainMenu()
    {
        SceneManager.UnloadSceneAsync("MainMenu");
        // Add Debug.Log here
    }
}

Hint

Use Debug.Log("GameLevel scene loaded") inside LoadGameLevel() and Debug.Log("MainMenu scene unloaded") inside UnloadMainMenu().

Practice

1. What does loading a scene in Unity do?

easy

A. It changes what the player sees by switching or adding scenes.

B. It deletes all game objects permanently.

C. It saves the current game progress automatically.

D. It pauses the game without changing the view.

Solution

1. Step 1: Understand scene loading purpose

   Loading a scene changes the visible content by switching or adding new scenes.

2. Step 2: Compare other options

   Deleting objects, saving progress, or pausing are unrelated to scene loading.

3. Final Answer:

   It changes what the player sees by switching or adding scenes. -> Option A

4. Quick Check:

   Scene loading = change visible scenes [OK]

Hint: Loading scenes changes what player sees [OK]

Common Mistakes:

• Confusing loading with saving game progress
• Thinking loading deletes objects
• Assuming loading pauses the game

2. Which of the following is the correct syntax to load a scene additively in Unity using C#?

easy

A. SceneManager.LoadScene("Level2", LoadSceneMode.Additive);

B. SceneManager.LoadSceneAdditive("Level2");

C. SceneManager.LoadScene("Level2", true);

D. SceneManager.AddScene("Level2");

Solution

1. Step 1: Recall Unity scene loading syntax

   The correct method is LoadScene with scene name and LoadSceneMode.Additive as parameters.

2. Step 2: Check each option

   Only SceneManager.LoadScene("Level2", LoadSceneMode.Additive); uses the correct method and enum for additive loading.

3. Final Answer:

   SceneManager.LoadScene("Level2", LoadSceneMode.Additive); -> Option A

4. Quick Check:

   LoadScene + LoadSceneMode.Additive = correct syntax [OK]

Hint: Use LoadScene with LoadSceneMode.Additive [OK]

Common Mistakes:

• Using non-existent methods like LoadSceneAdditive
• Passing boolean instead of LoadSceneMode enum
• Confusing AddScene with LoadScene

3. What will happen if you run this code snippet in Unity?

SceneManager.LoadScene("Menu");
SceneManager.LoadScene("Game", LoadSceneMode.Additive);

medium

A. Only the "Game" scene will be loaded, replacing "Menu".

B. Only the "Menu" scene will be loaded, ignoring the second call.

C. Both "Menu" and "Game" scenes will be loaded together.

D. An error will occur because you cannot load two scenes in a row.

Solution

1. Step 1: Understand default and additive loading

   The first call loads "Menu" scene normally (single mode), replacing current scenes. The second call loads "Game" additively, adding it without unloading "Menu".

2. Step 2: Analyze the sequence

   Since the second call uses additive mode, both scenes "Menu" and "Game" will be loaded together.

3. Final Answer:

   Both "Menu" and "Game" scenes will be loaded together. -> Option C

4. Quick Check:

   Additive loading adds scene without unloading [OK]

Hint: Additive mode loads scene without unloading others [OK]

Common Mistakes:

• Assuming first load is replaced by second always
• Thinking additive unloads previous scenes
• Believing multiple loads cause errors

4. Identify the error in this Unity C# code for unloading a scene:

SceneManager.UnloadScene("Level1");

medium

A. UnloadScene is deprecated; use UnloadSceneAsync with scene name.

B. UnloadSceneAsync should be used instead of UnloadScene.

C. There is no error; the code unloads the scene correctly.

D. UnloadScene requires a Scene object, not a string.

Solution

1. Step 1: Check Unity API for unloading scenes

   SceneManager.UnloadScene requires a Scene object as parameter, not a string name. No overload accepts string directly.

2. Step 2: Analyze the code

   The code will not compile. Correct usage: Scene scene = SceneManager.GetSceneByName("Level1"); SceneManager.UnloadScene(scene);

3. Final Answer:

   UnloadScene requires a Scene object, not a string. -> Option D

4. Quick Check:

   UnloadScene(Scene), not (string) [OK]

Hint: UnloadScene requires Scene object, not string [OK]

Common Mistakes:

• Passing string name instead of Scene object
• Thinking UnloadScene is deprecated
• Assuming the code runs without error

5. You want to load a new scene "Battle" without unloading the current "Town" scene, but only if "Battle" is not already loaded. Which code snippet correctly does this in Unity?

hard

A. SceneManager.UnloadSceneAsync("Town");
SceneManager.LoadScene("Battle");

B. if (!SceneManager.GetSceneByName("Battle").isLoaded) {
SceneManager.LoadScene("Battle", LoadSceneMode.Additive);
}

C. SceneManager.LoadScene("Battle", LoadSceneMode.Single);

D. SceneManager.LoadScene("Battle");

Solution

1. Step 1: Check if "Battle" scene is already loaded

   Use SceneManager.GetSceneByName("Battle").isLoaded to verify if scene is loaded.

2. Step 2: Load "Battle" additively if not loaded

   If not loaded, call LoadScene with LoadSceneMode.Additive to keep "Town" scene loaded.

3. Final Answer:

   if (!SceneManager.GetSceneByName("Battle").isLoaded) { SceneManager.LoadScene("Battle", LoadSceneMode.Additive); } -> Option B

4. Quick Check:

   Check loaded + additive load = correct approach [OK]

Hint: Check isLoaded before additive load [OK]

Common Mistakes:

• Loading scene in single mode, unloading current scene
• Not checking if scene is already loaded
• Unloading current scene before loading new one