Transfer a gameobject between specific scenes

[anon20000101]

I am trying to implement something but i can’t find a solution.

What i want to do is.

• There is two scenes: CharacterScene and GameScene
• CharacterScene has a gameobject “player” and a button
• When i click the button, GameScene will be loaded

The button includes this code

public class StartTheGame : MonoBehaviour
{
    public void LoadGame()
    {     
        GameObject player = GameObject.Find("Player");

        if (player != null)
        {
            SceneManager.LoadScene("GameScene");

            DontDestroyOnLoad(player);
        }
    }
}

The problem is this

• When i click the button, player gameobject will perfectly transfered to GameScene but
• When i return to CharacterScene there is 2 player gameobjects

The character will be fully customizable so having two player will be a problem.
Also, the player is staying to any scene i change.

How can i implement the player transfer to specific scenes?
Also how can i keep only one player gameobject when i return to CharacterScene?

[Kurt-Dekker]

When i return to CharacterScene there is 2 player gameobjects

The above is a faulty singleton implementation because it uses GameObject.Find(), and probably for other reasons too.

Remember also that scenes do not load until the next frame, but that may not matter here.

---

Remember the first rule of GameObject.Find():

Do not use GameObject.Find();

More information: Regarding GameObject.Find · UnityTipsRedux

More information: Why cant i find the other objects?

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Here is some singleton / GameManager pattern that I frequently use:

ULTRA-simple static solution to a GameManager:

I need to save the score when the scene resets

I see this question enough that I decided to answer it once and for all and you can tell me if I have done so successfully! Here is what I have created, two files: ULTRA-simple static solution to a GameManager: https://gist.github.com/kurtdekker/50faa0d78cd978375b2fe465d55b282b Each file has notes at the top of it telling you how to use it. Can you please look it over and see if it makes sense? You will need to call GM.InitGame() at the start of every game, and call GM.AddScore() to add poin…

https://gist.github.com/kurtdekker/50faa0d78cd978375b2fe465d55b282b

OR for a more-complex “lives as a MonoBehaviour or ScriptableObject” solution…

Simple Singleton (UnitySingleton):

Some super-simple Singleton examples to take and modify:

Simple Unity3D Singleton (no predefined data):

https://gist.github.com/kurtdekker/775bb97614047072f7004d6fb9ccce30

Unity3D Singleton with a Prefab (or a ScriptableObject) used for predefined data:

https://gist.github.com/kurtdekker/2f07be6f6a844cf82110fc42a774a625

These are pure-code solutions, DO NOT put anything into any scene, just access it via .Instance!

The above solutions can be modified to additively load a scene instead, BUT scenes do not load until end of frame, which means your static factory cannot return the instance that will be in the to-be-loaded scene. This is a minor limitation that is simple to work around.

If it is a GameManager, when the game is over, make a function in that singleton that Destroys itself so the next time you access it you get a fresh one, something like:

public void DestroyThyself()
{
   Destroy(gameObject);
   Instance = null;    // because destroy doesn't happen until end of frame
}

There are also lots of Youtube tutorials on the concepts involved in making a suitable GameManager, which obviously depends a lot on what your game might need.

OR just make a custom ScriptableObject that has the shared fields you want for the duration of many scenes, and drag references to that one ScriptableObject instance into everything that needs it. It scales up to a certain point.

And finally there’s always just a simple “static locator” pattern you can use on MonoBehaviour-derived classes, just to give global access to them during their lifecycle.

WARNING: this does NOT control their uniqueness.

WARNING: this does NOT control their lifecycle.

public static MyClass Instance { get; private set; }

void OnEnable()
{
  Instance = this;
}
void OnDisable()
{
  Instance = null;     // keep everybody honest when we're not around
}

Anyone can get at it via MyClass.Instance., but only while it exists.

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And here are some notes on additive scene loading is one possible solution:

Right way for performance, divide scene?

I always favor breaking the scenes up and loading additively. reduces overall memory consumption lets multiple team members trample on each other less often ensures clean “reset” of all objects in a fresh loaded scene I’m working on a game now where we each have our own “content” level, the level we’re working on. the content scene has all the lighting baked in. Just press play and that level has one script that additively loads: music scene (just an audiosource on autoplay) the …

Right way for performance, divide scene?

Glad you asked… going this route definitely requires slightly-higher awareness of what scene is what. In no particular order, responding to you questions, When the game or level is over, I try to go to a fresh “end level” scene (not additively!) and clear everything else out (except overall ongoing game manager obviously, as a singleton) when the game gets paused I stop time and bring up a pause scene that sorts above all else, then unload it and restart the time. OR if you quit, I just …

Problem with canvas & UI prefabs

There are underlying reasons this happened and you can track it down by examining everything about each scene’s canvas setup and scaling that are different from the other. But keep in mind it might not be super-easily to address it in the general case, especially if you start partitioning your UI into chunks. An alternate workflow is to put chunks of your UI into separate scenes and then load those scenes additively. For instance you might have the following scenes, all loaded additively: c…

A multi-scene loader thingy:

Unity additive scene loading example - Pastebin.com

My typical Scene Loader:

https://gist.github.com/kurtdekker/862da3bc22ee13aff61a7606ece6fdd3

Other notes on additive scene loading:

Removing Duplicates on Load Scene

Why not remove the player from ALL your scenes, put him in his own separate scene, then load scenes additively? That way you don’t even need a Player prefab at all, just have a Player scene and load him additively. I tend to break up all my games into partial scenes, all additively loaded by the game manager: UI player enemy manager other stuff? and then finally I load the content scene. The first batch of screens all have scripts that do nothing until the content scene appears and they kn…

Timing of scene loading:

Function called from preloader script doesn't change parent of gameobject (in the second scene)

If line 8 relies on something being present from the scene load in line 7 (in GameController), it won't be: scenes are loaded at the end of frame and would never be available until the next frame, at the very earliest. You can trivially make void Start() into a coroutine by declaring it to return an IEnumerator, then put a while loop (with a yield return null; in it!!!) to wait until the scene loads and you find the "Trains" object, then proceed. Obviously you would need to interlock other t…

Also, if something exists only in one scene, DO NOT MAKE A PREFAB out of it. It’s a waste of time and needlessly splits your work between two files, the prefab and the scene, leading to many possible errors and edge cases.

Two similar examples of checking if everything is ready to go:

Daily Events and content changes

I think multiple scenes are definitely worth chasing. You need to make everything in your game tolerant of perhaps not having stuff ready at the same time, and you have to track things that you need only ONE of: Camera (Main) Audio Listener EventSystem I like to put all of those in the BASE scene if possible, then load other scenes like UI and pause and the level itself, etc. You have to sort of figure out which works for you. You can actually make Start() be a coroutine too, such as lookin…

Unit scripts calling Start function before other scripts

Indeed. I like to use a lot of additively-loaded scenes, so I tend to code my individual item controllers (including the player controller) so that they are happy to wait around if other stuff isn’t ready yet. You can make Start() into a coroutine, which is a super-easy way to get this kind of lazy-sloppy startup that is extremely tolerant of late loading and uneven loading. // typical base framework for all entities bool ready; IEnumerator Start () { // don't proceed unt…

[Baste]

@Kurt-Dekker Do you have a bunch of pre-written posts that you copy-paste? Or do you just use some AI you’ve trained on your own posts?

Or are you actually typing out an essay like 30 times a day?

[Kurt-Dekker]

@Baste

Do you have a bunch of pre-written posts that you copy-paste?

I do!

Besides helping others, the main point of me doing this is for ME to learn interesting and new things about Unity.

This works really well in fact!

But there is a huge corpus of posters with mundane issues (NullRef) or else those who have gone far beyond their basic understanding of Unity object / asset lifecycles, and that’s where the above copy / pasta comes from.

You will note that in all but the most-trivial “I have error CS#### halp meee!!!” type of posting, there is often a sentence or two that I write at the top.