Best practices for coexisting, overlapping worlds?

novaplusplus

Hi there.

So, I'm presently trying to figure out the best ("best") way to handle a design goal of mine. Simply put, I want to have two separate worlds with their own physics and render spaces. I'm fairly sure I could do this with render/physics layers, but managing every object on its own layer can quickly become a major fuss, so I was wondering if there is a better/more automatic way to do it (involving viewports, I assume...)

I've done this before in Unity using the layers method but godot is my true love now and I want to pick everyone's brains a bit to figure out what might be the best way to do what I want.

cybereality

Yes, you can have as many worlds as you want with viewports. You can also have just one world, and have different separate areas with multiple cameras. It will just depend on how you want to display them. What does the screen look like?

novaplusplus

In my case, the eventual goal will be a display monitor in one that can be brought to fullscreen, showing the other world entirely. The exact presentation is flexible.

I have not fully set this up yet, but my preliminary setup for actually displaying the viewports is as follows (note that I am working with my own build of godot 4.x because I am impatient and live dangerously ? so the gdscript syntax is the bleeding edge flavor, but the principles should be the same)

extends Node2D

@export var viewport_path: NodePath
@onready var _viewport_sprite := $ViewportSprite as Sprite2D
@onready var _viewport := get_node(viewport_path) as SubViewport
	
func _process(_delta):
	var win_size := DisplayServer.window_get_size()
	if _viewport.size != win_size:
		_viewport.size = win_size
		_viewport_sprite.texture = _viewport.get_texture()

I have absolutely no idea if this is a good way to do it. Hence this thread, I guess! The intent is to have one of these for each viewport and toggle visibility and whatnot as needed.

Beyond that I'm also trying to figure out how to properly use the World resource. It doesn't have as many properties as I'd expect, or maybe does it "just work"? This is unfamiliar territory for me, so I am a bit timid about it.

cybereality

I don't use Godot 4.0, so I'm not sure about the code. But in general, you can create the viewports in the editor, the code would just be needed to swap which one was displayed, or resize them if you want split screen. Or in your case, you can get the viewport texture and display it on an object, like a security camera monitor, etc. This is fairly straight-forward.

I think the correct way is to create a world on the viewport and check the enable own world property. This will separate them. But it is not well documented and I never figured out how it worked. For my demo, I create all the viewports in code, and then programmatically call remove_child and add_child to move specific nodes into certain viewports. This is better for me as I can work in the editor like normal and not deal with having viewport containers mess up my work flow. But if you could figure out how to create the own world I think that would be better.

TwistedTwigleg

@novaplusplus said: In my case, the eventual goal will be a display monitor in one that can be brought to fullscreen, showing the other world entirely. The exact presentation is flexible.

I have not fully set this up yet, but my preliminary setup for actually displaying the viewports is as follows (note that I am working with my own build of godot 4.x because I am impatient and live dangerously ? so the gdscript syntax is the bleeding edge flavor, but the principles should be the same) (Code here) I have absolutely no idea if this is a good way to do it. Hence this thread, I guess! The intent is to have one of these for each viewport and toggle visibility and whatnot as needed.

I would recommend adjusting this slightly for better performance, so you can avoid having this code run every frame. I do not know the exacts of what it would look like in Godot 4.0, but in Godot 3.X you can do this:

func _ready():
	get_tree().root.connect("size_changed", self, "on_root_size_changed")
	on_root_size_changed()

func on_root_size_changed():
	# if you want to have the same size as the game display
	# (should be the same as window size if your stretch mode isn't set to keep or scaling mode is not set to 2D)
	_viewport.size = get_tree().root.size()
	_viewport_sprite.texture = _viewport.get_texture()

The advantage of doing it this way is that the code will only execute when the window changes size, so it is only run when needed instead of every frame, saving some performance. You do need to call it initially in _ready but outside of that, it should just be automatically updated

Beyond that I'm also trying to figure out how to properly use the World resource. It doesn't have as many properties as I'd expect, or maybe does it "just work"? This is unfamiliar territory for me, so I am a bit timid about it.

In Godot 3.X, the world property in a Viewport just determines whether the children of the Viewport node are going to be in their own completely separate space or not. It does this automatically last I knew on the Viewport level, but I'm not 100% sure as I have not looked into the source code. I have made games that use multiple Viewports with completely separate worlds and I know that I didn't need to do anything special other than make sure each Viewport had it's own world.

novaplusplus

Aha, that signal is just the sort of knowledge I was hoping to glean from making this thread, thank you. I can figure out any differences in the newer gdscript from there.

I put together a test scene and it really does appear like it Just Works. The script is extremely simple and just instantiates both worlds in their respective viewports:

extends Node

func _ready():
	var w1 = load("res://world1.tscn").instantiate()
	$World1Container/View.add_child(w1)
	var w2 = load("res://world2.tscn").instantiate()
	$World2Container/View.add_child(w2)

I think I can work with this...

cybereality

@TwistedTwigleg said:
func _ready():
	get_tree().root.connect("size_changed", self, "on_root_size_changed")
	on_root_size_changed()

func on_root_size_changed():
	# if you want to have the same size as the game display
	# (should be the same as window size if your stretch mode isn't set to keep or scaling mode is not set to 2D)
	_viewport.size = get_tree().root.size()
	_viewport_sprite.texture = _viewport.get_texture()
The advantage of doing it this way is that the code will only execute when the window changes size, so it is only run when needed instead of every frame, saving some performance. You do need to call it initially in _ready but outside of that, it should just be automatically updated

Actually, the viewport texture is just a pointer and doesn't reallocate ever, even on resolution changes. You only need to get it once and it will stay valid the whole time.

func get_viewport_texture():
	yield(VisualServer, "frame_post_draw")
	var view_texture = viewport.get_texture()

novaplusplus

Thanks for the help everyone.

Currently I'm trying to get input cooperating. I know I know I should be using action defs but this is just for testing things - it works just fine when I run the scene in isolation or under the main viewport, but as soon as it's under the secondary one it no longer works:

func _unhandled_input(event):
	if event is InputEventKey:
		if !event.pressed and event.keycode == KEY_L:
			$Label.visible = !$Label.visible

I've been playing with the "disable input" and "handle input locally" options in various combinations but nothing seems to want to get through to it.

I suppose an alternative would be to make some sort of input server as an autoload and connect onto signals or axis outputs from it. This is what I get for trying to throw together a test camera quickly though, I guess.

cybereality

Viewports don't automatically pass input to children, so you need to proxy the functions. Add this on a upper level node (outside or above the viewport).

func _input(event):
	if viewport and is_inside_tree():
		viewport.input(event)
		
func _unhandled_input(event):
	if viewport and is_inside_tree():
		viewport.unhandled_input(event)

novaplusplus

Thank you, that worked~