Godot Async Load

Hi, my name is Luiz and I'm going to teach you how to make a load screen just like this one. I consider this an intermediary topic as we're going to deal with an asynchronous task. But anyone will be able to follow along and easily reproduce it.

The code for this project is in the description and it's available in the start state and the final state. If you want to follow along, open the start version with Godot.

All right, let's go.

Open the Menu scene and open its script Menu.gd. You'll notice we change scenes when the StartGame button is pressed.

We use the change_scene method from the Scene Tree to do this.

extends Control

func _on_StartGame_pressed() -> void:
	get_tree().change_scene("res://Game/Game.tscn")
	pass

func _on_Quit_pressed() -> void:
	get_tree().quit()
	pass

Now, let's take a look at what's in the Game scene. In order to simulate a big load, I generated a big black square image. It might look small here, but it's just because it's scaled-down. If we just change scenes as in the Menu.gd script we'll have to wait for a little.


My computer has an SSD, so if yours have a Hard Drive, this will take even longer.

We will use the class Thread that is built-in Godot to load this scene asynchronously. Let's do this. Open the Menu.gd script. Then let's create an instance of Thread.

var thread: = Thread.new()

Now we need a method that the thread can call. This method has to receive one argument and we will make it so this argument is the path of the scene we want to load.

func change_scene_async(path: String):
	var game_scene: PackedScene = load(path)
	get_tree().call_deferred("change_scene_to", game_scene)

So, this function receives a path, loads it expecting a PackedScene as result, and then defers the scene change to the SceneTree. Fairly simple, right?

The call_deferred is important because it's not safe to add or remove things from the Scene Tree while we're in a thread.

Now, we modify the _on_StartGame_pressed callback to use the thread.

func _on_StartGame_pressed() -> void:
	$Loading.show()
	thread.start(self, "change_scene_async", "res://Game/Game.tscn")

First, we show our loading spinner. Then, we use thread to call the change_scene_async **method.

The first argument of thread.start is the instance that has the function we want to call asynchronously. In this case, it's the same we're in. The second is the name of the method to call and the third is the argument to be passed down to the method.

And it's ready. Now if we start the project and click Start Game we'll see the spinner while we wait for the Game scene to be loaded.

Of course, you can use anything as your loading screen.

That's it for this video, thanks for watching.