How Scene Transitions Work in the Undertale-Changer Template: A Complete Technical Guide

Scene transitions in the Undertale-Changer Template are managed by a centralized subsystem where GameUtilityService.cs handles fade animations and scene loading via DOTween and Unity's SceneManager, while MainControl.cs configures per-scene behavior and automatic fade-in sequences.

The Undertale-Changer Template provides a production-ready scene management system for Unity-based Undertale fangames. This architecture encapsulates visual blackout fades, optional BGM muting, and asynchronous loading into a single static API call. All transition logic resides in two core scripts that coordinate UI overlay animations with Unity's scene lifecycle.

Architecture Overview

The template isolates transition logic in two primary locations:

• Assets/Scripts/UCT/Service/GameUtilityService.cs – Static utility class containing the fade animation engine, audio tweening, and scene loader (lines 1-150)
• Assets/Scripts/UCT/Core/MainControl.cs – Scene-specific configuration and fade-in initialization (lines 80-95)

This separation ensures global transition behavior remains consistent while allowing individual scenes to customize entry animations, pause states, and fade durations through Unity Inspector settings.

Core Components

GameUtilityService (Exit Sequence)

Located at Assets/Scripts/UCT/Service/GameUtilityService.cs, this static class provides the primary API for scene switching. The FadeOutAndSwitchScene method (lines 89-124) orchestrates the complete exit sequence:

1. Captures the sceneSwitchingFadeImage reference (the Canvas/InOutBlack UI Image)
2. Tweens BGM volume to zero when isBgmMuted is true (lines 98-108)
3. Sets SettingsStorage.Pause to true, freezing gameplay updates (line 115)
4. Uses DOTween to animate the overlay color toward the specified fadeColor over fadeTime seconds (lines 120-132)
5. Invokes the scene switch callback upon tween completion

The actual loading occurs in SwitchScene (lines 43-58), which handles both synchronous and asynchronous loading via SceneManager.LoadScene or SceneManager.LoadSceneAsync. This method performs critical housekeeping: clearing the fade image, updating the last-scene cache (unless excluded), restoring resolution via SetResolution, and clearing MainControl.isSceneSwitching.

MainControl (Entry Sequence)

Assets/Scripts/UCT/Core/MainControl.cs manages scene entry through its Start method (lines 80-95). Upon scene load:

1. Locates the InOutBlack Image under the Canvas
2. Checks isFadeTransitionEnabled—if false, skips fade initialization
3. Sets the image to Color.black (unless isFadeInDisabled is true)
4. Animates toward Color.clear using DOTween
5. Clears the pause flag after completion (unless isFadeInUnpaused is enabled)

Configuration fields serialized in the Unity Inspector include isFadeTransitionEnabled (global fade toggle), isFadeInDisabled (skip entry fade), and isFadeInUnpaused (keep gameplay running during fade-in).

Excluded Scenes Logic

The ExcludedScenes array (lines 24-27 in GameUtilityService.cs) prevents specific scenes from being recorded as the "last scene" in the history cache. By default, "Menu", "Rename", "Story", "Start", "Battle", and "GameOver" are excluded, ensuring the game returns to meaningful gameplay scenes rather than temporary states.

Step-by-Step Transition Flow

A complete scene transition executes the following pipeline:

1. Initialization: The current scene's MainControl.Start has already completed its fade-in sequence.
2. Trigger: Game code calls GameUtilityService.FadeOutAndSwitchScene with target scene parameters.
3. Audio Management: If isBgmMuted is true, the audio source volume tweens to 0 over the specified duration (instant if fadeTime equals 0).
4. Gameplay Pause: SettingsStorage.Pause sets to true to prevent gameplay updates during the visual transition.
5. Visual Fade: DOTween animates the InOutBlack Image color toward the target fadeColor (typically Color.black).
6. Scene Activation: Upon tween completion, SwitchScene invokes SceneManager.LoadSceneAsync (or synchronous equivalent).
7. Housekeeping: The system restores resolution settings and clears the isSceneSwitching flag.
8. Entry: The new scene's MainControl.Start method executes, performing the fade-in from black to clear.

Configuration Examples

To implement an instant transition without visual effects:

// Disable fades for this scene instance
MainControl.Instance.isFadeTransitionEnabled = false;
GameUtilityService.SwitchScene("Battle", isAsync: false);

To create a dramatic slow fade with custom colors:

GameUtilityService.FadeOutAndSwitchScene(
    scene: "GameOver",
    fadeColor: Color.red,
    isBgmMuted: true,
    fadeTime: 2.0f,
    isAsync: true
);

Practical Implementation Example

The following pattern demonstrates transitioning from a battle victory back to the main menu:

public void OnBattleVictory()
{
    // Fade to black over 0.5 seconds, mute BGM, load Menu asynchronously
    GameUtilityService.FadeOutAndSwitchScene(
        scene: "Menu",
        fadeColor: Color.black,
        isBgmMuted: true,
        fadeTime: 0.5f,
        isAsync: true
    );
}

This single call handles the complete sequence: initiating the black fade, tweening audio volume to zero, pausing game logic, loading the Menu scene, and preparing the new scene's fade-in cycle.

Summary

• Scene transitions are centralized in GameUtilityService.cs with static methods like FadeOutAndSwitchScene and SwitchScene.
• Visual fades use a UI Image (Canvas/InOutBlack) animated via DOTween, supporting custom colors and durations with optional BGM muting.
• Per-scene configuration resides in MainControl.cs, controlling whether fades play, if they pause gameplay, and entry behavior through serialized boolean fields.
• Automatic housekeeping includes resolution restoration, scene history management (with exclusions for menu/utility scenes), and pause state reset.
• Asynchronous loading prevents frame hitches during heavy scene loads while maintaining the visual blackout until loading completes.

Frequently Asked Questions

How do I disable fade effects for a specific scene?

Set the isFadeTransitionEnabled field to false in that scene's MainControl component through the Unity Inspector. Alternatively, call GameUtilityService.SwitchScene directly to bypass the fade animation system entirely and load immediately.

Why isn't my scene being recorded in the "last scene" cache?

Check if your scene name appears in the ExcludedScenes array within GameUtilityService.cs (lines 24-27). Scenes like "Menu", "Battle", and "GameOver" are excluded by default to prevent the game from returning to temporary states when using scene restoration features.

Can I keep gameplay running during the fade-in animation?

Yes. In the target scene's MainControl component, enable the isFadeInUnpaused boolean flag. This prevents the system from setting SettingsStorage.Pause during the fade-in sequence, allowing animations and game logic to continue while the visual fade completes.

What happens if I specify a fadeTime of 0?

When fadeTime is 0, DOTween executes the color change instantly with zero duration. If isBgmMuted is also true, the BGM volume sets to 0 immediately rather than tweening. The scene switch still occurs on the next frame after the instant fade completes.

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}