Build settings and scene order in Unity - Performance & Optimization

Performance: Build settings and scene order

MEDIUM IMPACT

This affects the initial loading time and memory usage of a Unity game by controlling which scenes load first and how many scenes are included in the build.

Managing which scenes are included and their load order in a Unity build

Unity

Only add necessary scenes to build settings and order them so the main scene loads first.

Reduces build size and ensures the main scene loads quickly, improving startup time.

📈 Performance GainSaves tens of MBs in build size and reduces initial load blocking by seconds.

Managing which scenes are included and their load order in a Unity build

Unity

Add all scenes to build settings regardless of usage and leave them unordered.

Including unused scenes increases build size and unordered scenes can delay loading of main content.

📉 Performance CostIncreases build size by tens of MBs and delays initial scene load, blocking rendering longer.

Performance Comparison

Pattern	Build Size Impact	Initial Load Time	Memory Usage	Verdict
All scenes included unordered	High (extra MBs)	Long (blocks rendering)	High	[X] Bad
Only needed scenes ordered	Low (minimal size)	Short (fast load)	Optimized	[OK] Good

Rendering Pipeline

Unity loads scenes in the order specified in build settings during startup. Scenes not included are excluded from the build, reducing load time and memory. The first scene loads synchronously, blocking rendering until ready.

→Build Process

→Initial Scene Load

→Memory Allocation

⚠️ BottleneckInitial Scene Load blocking rendering

Core Web Vital Affected

LCP

This affects the initial loading time and memory usage of a Unity game by controlling which scenes load first and how many scenes are included in the build.

Optimization Tips

1Only include scenes you need in build settings to reduce build size.

2Order scenes so the main gameplay scene loads first to speed startup.

3Avoid loading many scenes at once to prevent blocking rendering.

Performance Quiz - 3 Questions

What is the main performance benefit of ordering scenes correctly in Unity build settings?

A Faster initial scene load and reduced blocking time

B Better graphics quality

C Improved physics calculations

D More scenes load simultaneously

DevTools: Unity Profiler

How to check: Open Unity Profiler, run the game, and observe the loading time and memory usage during initial scene load.

What to look for: Look for long blocking times in the loading phase and high memory spikes indicating large build or many scenes loaded.

Practice

1. What does the Build Settings window in Unity control?

easy

A. Which scenes are included in the final game build

B. The resolution of the game window

C. The color scheme of the editor

D. The physics settings of the game

Solution

1. Step 1: Understand the purpose of Build Settings

   The Build Settings window lists scenes to include in the game build and their order.

2. Step 2: Identify what Build Settings controls

   It controls which scenes are packaged into the final game, not editor or physics settings.

3. Final Answer:

   Which scenes are included in the final game build -> Option A

4. Quick Check:

   Build Settings = Scenes included [OK]

Hint: Build Settings = scenes included in game build [OK]

Common Mistakes:

• Confusing Build Settings with editor appearance
• Thinking it controls physics or resolution
• Assuming it sets scene start order only

2. Which of the following is the correct way to add a scene to the build in Unity?

easy

A. Drag the scene file into the Build Settings window's Scenes In Build list

B. Right-click the scene in Project and select 'Add to Build'

C. Open the scene and press Ctrl+B

D. Rename the scene file to include 'build' in its name

Solution

1. Step 1: Recall how to add scenes to build

   In Unity, you add scenes by dragging them into the Scenes In Build list in Build Settings.

2. Step 2: Evaluate the options

   Only dragging the scene file into Build Settings is correct; other options are invalid or do nothing.

3. Final Answer:

   Drag the scene file into the Build Settings window's Scenes In Build list -> Option A

4. Quick Check:

   Add scene = drag to Build Settings [OK]

Hint: Add scenes by dragging into Build Settings list [OK]

Common Mistakes:

• Trying to add scenes by renaming files
• Using keyboard shortcuts that don't add scenes
• Expecting context menu to add scenes automatically

3. Given the following scenes in Build Settings in order: ["Menu", "Level1", "Level2"], what will SceneManager.LoadScene(1) load?

medium

A. The scene named "Menu"

B. The scene named "Level1"

C. The scene named "Level2"

D. An error because index 1 is invalid

Solution

1. Step 1: Understand scene indexing in Build Settings

   Scenes are indexed starting at 0 in the order listed in Build Settings.

2. Step 2: Identify scene at index 1

   Index 0 = "Menu", index 1 = "Level1", index 2 = "Level2".

3. Final Answer:

   The scene named "Level1" -> Option B

4. Quick Check:

   Index 1 = second scene = Level1 [OK]

Hint: Scene index starts at 0 in Build Settings [OK]

Common Mistakes:

• Assuming index 1 is the first scene
• Confusing scene names with indexes
• Thinking index 1 causes an error

4. You try to load a scene by index using SceneManager.LoadScene(3), but get an error. What is the most likely cause?

medium

A. SceneManager.LoadScene only accepts strings

B. You must use scene names, not indexes

C. The scene file is missing from the Project folder

D. The scene at index 3 is not added to Build Settings

Solution

1. Step 1: Understand scene indexing and Build Settings

   Scene indexes correspond to the order in Build Settings; index 3 means the fourth scene.

2. Step 2: Identify cause of error

   If index 3 is out of range, it means fewer than 4 scenes are added to Build Settings.

3. Final Answer:

   The scene at index 3 is not added to Build Settings -> Option D

4. Quick Check:

   Index out of range = scene missing in Build Settings [OK]

Hint: Check Build Settings scene count before loading by index [OK]

Common Mistakes:

• Thinking indexes are unrelated to Build Settings
• Believing LoadScene only accepts names
• Assuming missing file causes this specific error

5. You want your game to start with the "Intro" scene, but currently the "MainMenu" scene is first in Build Settings. How can you fix this without renaming scenes?

hard

A. Call SceneManager.LoadScene("Intro") in the first scene's script

B. Change the scene file name to "00_Intro"

C. Drag the "Intro" scene to the top of the Scenes In Build list

D. Remove "MainMenu" from Build Settings

Solution

1. Step 1: Understand scene start order in Build Settings

   The first scene in the Scenes In Build list is the one that starts when the game runs.

2. Step 2: Adjust scene order without renaming

   Drag the "Intro" scene to the top of the list to make it the first scene loaded.

3. Final Answer:

   Drag the "Intro" scene to the top of the Scenes In Build list -> Option C

4. Quick Check:

   First scene in Build Settings = start scene [OK]

Hint: First scene in Build Settings list starts game [OK]

Common Mistakes:

• Renaming files instead of reordering scenes
• Removing scenes unnecessarily
• Relying only on script calls without build order