Preload scene in unity

Question

I have a game with two scenes, menu and maingame. I have uploaded the game to googleplay. However when I open the game and click on the play button in the menu scene, the next scene (maingame) takes about 4-5 seconds to load. Is there any way to load the maingame along with the menu so that there is no delay in loading?

EDIT

I have added code to the MainMenu.cs file so that when the game starts the LoadSceneAsync function is called and allowSceneActivation is set to false. Once the "play" button is pressed, the activation is set to true. The first time the game loads, there is still a bit of delay however if the player dies and I go the main menu and press play again, there is no delay.

AsyncOperation async;

void Start()
{        
    async = SceneManager.LoadSceneAsync(1);       
    async.allowSceneActivation = false;
}

public void PlayBtnPressed()
{
   async.allowSceneActivation = true;
   AudioManager.audiomanager.Play("PlayButton");       
}

Answer 1

Scene Loading

Basic

Tested this in a new project. The idea is to start scene preloading when Return button is pressed and save AsyncOperation that is doing it, disallow scene activation for it and allow it when you need the scene to be loaded as soon as it's ready.

I would expect it to be loaded into memory, be careful if you are RAM-bounded because both scenes will take up memory space until one is unloaded.

Reproduce:

1. Create a new project.
2. Create 2 scenes:
   • "menu"
   • "maingame"
3. Add both scenes to Build Settings.
4. Open "menu" scene.
5. Create GameObject and add PreloadSceneInUnity component to it.
6. Enter playmode.
7. Press Return and see "maingame (is loading)" in Hierarchy window.
8. Press Space - "maingame" scene will open.

Code

Git: Preload scene in unity

using System.Collections;

using UnityEngine;
using UnityEngine.SceneManagement;

public class PreloadSceneInUnity : MonoBehaviour
{
    [SerializeField] private string _sceneName = "maingame";
    public string _SceneName => this._sceneName;

    private AsyncOperation _asyncOperation;

    private IEnumerator LoadSceneAsyncProcess(string sceneName)
    {
        // Begin to load the Scene you have specified.
        this._asyncOperation = SceneManager.LoadSceneAsync(sceneName);

        // Don't let the Scene activate until you allow it to.
        this._asyncOperation.allowSceneActivation = false;

        while (!this._asyncOperation.isDone)
        {
            Debug.Log($"[scene]:{sceneName} [load progress]: {this._asyncOperation.progress}");

            yield return null;
        }
    }

    private void Update()
    {
        if (Input.GetKeyDown(KeyCode.Return) && this._asyncOperation == null)
        {
            Debug.Log("Started Scene Preloading");

            // Start scene preloading.
            this.StartCoroutine(this.LoadSceneAsyncProcess(sceneName: this._sceneName));
        }

        // Press the space key to activate the Scene.
        if (Input.GetKeyDown(KeyCode.Space) && this._asyncOperation != null)
        {
            Debug.Log("Allowed Scene Activation");

            this._asyncOperation.allowSceneActivation = true;
        }
    }
}

---

Advanced

If you are not satisfied with how scene loading works in UnityEngine.SceneManagement - I suggest you take a look at Addressables package that Unity provides, it has support for scene loading as well, but be aware that it's a lot more complicated to get into and there is a learning curve that requires to learn quite a few more things before scene loading.

Answer 2

You can load the next scene asynchronously using SceneManager.LoadSceneAsync() using coroutines. You can use this strategy on a splash / loading screen if you're wanting to see it load before showing the menu.

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

public class Example : MonoBehaviour
{
    void Update()
    {
        // Press the space key to start coroutine
        if (Input.GetKeyDown(KeyCode.Space))
        {
            // Use a coroutine to load the Scene in the background
            StartCoroutine(LoadYourAsyncScene());
        }
    }

    IEnumerator LoadYourAsyncScene()
    {

        AsyncOperation asyncLoad = SceneManager.LoadSceneAsync("Scene2");

        // yield to other processes until the scene is loaded
        while (!asyncLoad.isDone)
        {
            yield return null;
        }

        // Do something here like enabling the play button or closing the splash/loading screen
    }
}

Code example from: https://docs.unity3d.com/ScriptReference/SceneManagement.SceneManager.LoadSceneAsync.html

EDIT: As has been indicated in the comments, if you want to control when the scene loads, you can use the allowSceneActivation flag on the above AsyncOperation object. asyncLoad.allowSceneActivation = false; When you want it to load the next scene: asyncLoad.allowSceneActivation = true;