Scene loading and unloading in Unity

Introduction

Loading and unloading scenes lets you change what the player sees and interacts with. It helps keep your game organized and saves memory by only using what is needed.

When moving from one level to another in a game.

When opening or closing menus or UI screens.

When loading parts of a large world step-by-step.

When freeing up memory by removing scenes no longer needed.

Syntax

Unity

using UnityEngine.SceneManagement;

// To load a scene by name
SceneManager.LoadScene("SceneName");

// To load a scene additively (keep current scenes)
SceneManager.LoadScene("SceneName", LoadSceneMode.Additive);

// To unload a scene by name
SceneManager.UnloadSceneAsync("SceneName");

Use LoadSceneMode.Additive to load a scene without removing the current one.

Unloading scenes frees memory but only works on scenes loaded additively.

Examples

This loads the "MainMenu" scene and replaces the current scene.

Unity

SceneManager.LoadScene("MainMenu");

This loads "Level2" on top of the current scene, so both run together.

Unity

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

This unloads the "Level1" scene asynchronously to free memory.

Unity

SceneManager.UnloadSceneAsync("Level1");

Sample Program

This script listens for key presses. Pressing 'L' loads a scene called "GameScene" without removing the current scene. Pressing 'U' unloads "GameScene" to free memory.

Unity

using UnityEngine;
using UnityEngine.SceneManagement;

public class SceneSwitcher : MonoBehaviour
{
    void Update()
    {
        if (Input.GetKeyDown(KeyCode.L))
        {
            // Load the "GameScene" additively
            SceneManager.LoadScene("GameScene", LoadSceneMode.Additive);
            Debug.Log("GameScene loaded additively.");
        }

        if (Input.GetKeyDown(KeyCode.U))
        {
            // Unload the "GameScene"
            SceneManager.UnloadSceneAsync("GameScene");
            Debug.Log("GameScene unloading started.");
        }
    }
}

Important Notes

Always check that the scene name matches exactly what is in your build settings.

Loading scenes additively is useful for UI or multi-part worlds.

Unloading scenes is asynchronous, so it happens over time without freezing the game.

Summary

Use SceneManager.LoadScene to load scenes by name.

Use LoadSceneMode.Additive to keep current scenes when loading new ones.

Unload scenes with SceneManager.UnloadSceneAsync to save memory.

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