Scenes & Level Structure

Scenes Are Like Lightweight Levels

In Unreal, a Level is a complete world with its own streaming setup. In Unity, a Scene is more lightweight — it's a container for GameObjects that can be loaded and unloaded independently.

Scene Loading

Unreal uses World Partition and Level Streaming. Unity uses SceneManager with two modes: Single (replaces current scene) and Additive (loads alongside current scene).

// Unreal: Load a level
#include "Kismet/GameplayStatics.h"

// Hard transition
UGameplayStatics::OpenLevel(this, TEXT("MapName"));

// Level streaming
ULevelStreamingDynamic::LoadLevel(
    this, TEXT("SubLevelName"),
    FVector::ZeroVector, FRotator::ZeroRotator);

using UnityEngine.SceneManagement;

// Single mode — replaces current scene
SceneManager.LoadScene("GameLevel");

// Additive — loads alongside current scene
SceneManager.LoadSceneAsync("UI_Overlay",
    LoadSceneMode.Additive);

// Unload an additive scene
SceneManager.UnloadSceneAsync("UI_Overlay");

Persistent Objects

In Unreal, the GameInstance persists across level loads. In Unity, you use DontDestroyOnLoad to keep a GameObject alive across scene transitions.

// Unreal: GameInstance persists across levels
UCLASS()
class UMyGameInstance : public UGameInstance
{
    GENERATED_BODY()
public:
    UPROPERTY()
    int32 PlayerScore = 0;

    UPROPERTY()
    FString PlayerName;
};

// Unity: Singleton that survives scene loads
public class GameManager : MonoBehaviour
{
    public static GameManager Instance;
    public int PlayerScore;
    public string PlayerName;

    void Awake()
    {
        if (Instance != null)
        {
            Destroy(gameObject);
            return;
        }
        Instance = this;
        DontDestroyOnLoad(gameObject);
    }
}

Multi-Scene Workflow

Unity's additive scene loading enables a powerful pattern: keep your managers in a persistent scene and load content scenes on top. This is similar to Unreal's level streaming but more explicit.

using System.Collections;
using UnityEngine;
using UnityEngine.SceneManagement;
using UnityEngine.UI;

public class SceneLoader : MonoBehaviour
{
    public Slider progressBar;

    public void LoadScene(string sceneName)
    {
        StartCoroutine(LoadAsync(sceneName));
    }

    IEnumerator LoadAsync(string sceneName)
    {
        AsyncOperation op = SceneManager.LoadSceneAsync(sceneName);
        op.allowSceneActivation = false;

        while (op.progress < 0.9f)
        {
            progressBar.value = op.progress;
            yield return null;
        }

        progressBar.value = 1f;
        yield return new WaitForSeconds(0.5f);
        op.allowSceneActivation = true;
    }
}