Godot 101 - Part 4: Instancing Scenes

Key Takeaways

welcome to part four of good 101 in this video we will be talking about taking a scene that you have created and showing you how to instance it or create multiple instances of it as always if you haven't watched the previous videos please go back and do that before watching this one because we are building on the things we've made before all right let's get started okay here's our bouncing Sprite and it's all working well but now the question is what if we want to make a bunch of these what if I want to spawn multiple of these Sprites and have them all bouncing around the screen well you might think you could go over here and just duplicate this node right so if I right click on this and say duplicate oh now I'm going to get this error and I'll zoom in a bit so you can read it the problem is that a scene is a tree right and there can only be one node that's the root of the tree or the one at the top this this node can have children things that are underneath it that are attached to it but it can't have something at the same level as it and we don't want to make another Sprite that's a child of this Sprite because then they would be joined together right the the child of this Sprite would use its position and all that kind of stuff I want another unique Sprite that is equivalent to this one but I don't want to go and make a bunch more Sprite scenes and and duplicate my code and all that kind of stuff well one of the powerful things about scenes and remember a scene is just a collection of nodes our scene here just has this one node but you could have a scene that could have you know multiple nodes in it and those those nodes together with any scripts that are attached to them can be thought of and actually are an object and if you've done objectoriented programming before you know that that allows you to create multiple of the same object to use that object as a definition for creating more and more objects of the same type and that's what we're going to do with this Sprite scene I'm going to write some code to have gdau just spawn a bunch of these Sprite scenes okay so to do that we're going to start by making another new scene I just click on scene new scene and to this scene I'm going to add a node and I'm just going to add the simplest node possible just a node node that's all I care about I just want this this is just a generic node has almost no properties at all but it's just there to serve as the root of my scene and I'm going to click on the name here and I'm going to call this main this is going to be my main scene so if I save it I'm going to save it with the name Main and then I'm going to hit not the play scene button but I'm going to hit this button this is to play the whole project and when you click on this it's going to say you haven't de defined a main scene which scene is the one that starts when you start the project so I'm going to say I want to do that right now so I'm going to click select and I'm going to select the main scene for that so now when I hit Play and play the project my main scene will open of course there's nothing in here just yet so now let's add a script to this right so we're going to add a script we're going to call it main. GD that's fine okay as usual let's remove our comments and we're ready to start coding okay and in this script we can have just like in our Sprite script we could have things that we can have variables we can have uh things that happen when the scene comes into existence in the ready and we could have the underscore process function do things every frame any of that stuff what we want to do is we want to have we want to have a reference to that Sprite scene let's save this sprite. tscn okay now I could do this I'm going to show you what we're going to do let's call this we'll just call this Sprite we want to load this Sprite scene that's saved this one over here as the file we're going to use the preload function okay and what the preload function does is it lets you name some resource and this is the one we want and so I could rightclick on this and choose copy path and then if I go over here and hit paste this is the path to that Sprite scene file and all the resources that you have in your in your gido project are going to be listed like this starts out with Rees which stands for resource uh and just like a URL on the web colon SL slash and then the path to the object in a more complicated project we might have lots and lots of files so we're going to have we would organize them into folders and you would just right if you had a a scenes folder you know you would put it like that but this will be the the this will load our scene and put it in this variable now the problem too that happens is that what order things happen in is important and you want to make sure that if you do something in the ready function that it is actually that it's actually been loaded and is ready to go and so we're going to put on ready here and what on ready does that's going to ensure that this variable is ready and has been loaded off the dis when we're in the ready function and it's not going to give us an error because it hasn't gotten around to doing it yet so in our ready function we just want to spawn a bunch of these and so to spawn one of these Sprites we would just say instance okay that's going to take this Sprite scene and create an instance of it if I hit play oh we don't see anything why is that well that's because we have created this Sprite instance so we've made one of these but we need to add it to our tree so we're going to say add child and that because we're running this on Main that's going to add it as a child of the main node and when we hit play now we have one Sprite and if you want to look we can go over here to the debugger you can actually see if you look at the remote inspector the remote inspector lets you look at the scenes and the nodes that are currently live that are running right now so if we look under here we have there's our main node and underneath of it is a Sprite if I click on Sprite you can see look at that as the position is changing and the rotation is changing as it runs around screen so now if we want to spawn more of these we can just put this in a loop so if I just say for I in range let's just count to 10 and I'm going to put this in a loop so we're just going to count to 10 and add a bunch of sprite nodes to the scene and there you go it just spawned 10 of them and they're all going to do what they're supposed to do and we can look real quick here just to show show you what happens in the tree now if we look at our tree we can see we've got make this a little bigger we've got 10 Sprite children and gdau went ahead and auton named them because they all have to have unique names but they're all and we can click on them and inspect them and see what they're all doing and what's cool is we can actually do that with quite a lot of them right it'll work totally fine and that's it and as we get further into good development that's how you're going to see we're going to do things like bullets and mobs and things like that where you're just going to set up a scene that describes all the functionality of how any particular object in your game works and then in whatever scene you want them to appear you're just going to instance them as you need them do various things with them whatever you want to do that'll do it for this video in the next one we will start looking at some of the other node types and some of the things you can do with them so I'll see you next time thanks for watching