Additive Async Multi-Scene Loading in Unity

today we're going to build a solution that allows us to bootstrap a game with a persistent scene and additively load groups of scenes together at the same time what I want to achieve is to have one scene that holds services and objects that will exist for the lifetime of the game and then load in gameplay UI environments and cinematics as different scenes that comprise a scene group a scene group could be just one scene or it could be 10 or more let's see how we can get this done all right to start off today I want to import a third-party Library this is the scene reference library it lets us access scenes directly without having to use a bunch of string names it has a lot of other features too so let's bring that into the project quickly in unity you can go into your package manager hit the plus icon and import by get URL I'm importing version 4.0 this is going to give us a new type called scene reference it has properties like name and path you can also configure it a little bit if you head into project settings under scene reference you'll see some debug settings it's worth noting that this Library also supports addressables so let's see how we can use this in unity because I want to load my scenes as groups of scenes I'm going to Define some metadata about them the first thing I want to do is classify them by type so I can treat some of them differently for example a scene that I Mark as active scene will actually set that to be the active scene so that will become the target of any new game objects that are instantiated by scripts we can have new class called scene data that will keep all of the data about a scene and the first thing we can put in there is this new type scene reference for ease of use let's have a shortcut property here that just gives us direct access to the name of the scene and then let's also have a property for its type so now we can say a few things about each scene let's assemble them into a scene group a scene group can have a list of scene data let's create a helper for ourselves that'll return the name of a scene based on its type and we could just use Link for this we can use a first or default that's probably all the data we need right now we can come back and add a few more things to this later if necessary so let's have a look at how we can make use of this data I've got a new class here scen group manager now this is not a monob behavior just a pure CP class I want it to be able to publish a few events for us so whenever we load a scene unload a scene or we load an entire scene group I want to publish an action we're also going going to need a reference to the active scene group whichever one we've currently Got Loaded most methods from unity's scene manager return in async operation I want to collect all of these return types into a group that we can perform actions and Logic on let's have a struct here while we keep a readon list of all these async operations can just call it operations The Constructor can take the capacity and just create a new list for us I want two public properties the first one I want to be able to tell us a float value of the progress of all all the operations every async operation has a progress property let's just get the average of them using link let's have one more public property that will tell us if they're all finished async operations also have an isone property now we can use this new struct up in our main class when we're loading an unloading scenes so let's create two methods here the first one load scenes is going to be async returns a task it's going to accept a scene group a special type called I progress and a Boolean that will define whether or not we're going to reload scenes that actually are already loaded you could always set that to true if you wanted some duplicates now we just need a very basic unload scenes because we already know what the active scene group is we don't really need to pass in more parameters let's quickly divert to look at this I progress interface there's actually nothing too crazy about this this is a very simple interface that's part of net it can hold any type te and it actually only has one method you can see at the bottom there which is report typical use is that you use the report method to actually report on the progress being made so for this purpose I've made a very simple implementation of it it's an i progress type float called loading progress every time we get a report we're going to publish an event which is just the ratio of progress we've made so let's come back to our load scenes method and first of all let's set our active scene group to the group that we pass into the method I want a variable that's going to store any loaded scenes that are still here after we're done running the unload scenes method so that might be our bootstrapper or active gameplay scene perhaps depends on your game we'll get to that in a moment for now after we're done unloading the scenes let's first of all get a count of what scenes are still open so we can use the scene manager scene count property for that then we can iterate over all of these scenes and one by one we'll add them into this loaded scene list let's figure out how many scenes are actually in the active scene group that we just passed in and then let's create a new async operation group for them we'll just scroll down a little bit here so we have some more breathing room now we can get to the actual loading operations so we're just going to iterate over all of the scenes that we're going to load we can just make a for Loop that's going to just count up to the total amount of scenes that we have to operate on let's first get a variable with the scene data for the first scene if this scene is a duplicate of a scene that's already loaded and we said there's no dupes let's just continue and Go to the next iteration otherwise let's start loading the scene asynchronous ly and get a handle on that operation and then we're going to put this operation into our async operation group variable we can just add it directly to the list there once that's done let's publish an event that says that we've started to load this particular scene now before we move on from here I just want to point out a few things first of all I'm using the Path property of the scene reference type when we're loading the scene async and I'm also going to load all of these scenes additively the only scene I ever want to have loaded in single mode is my bootstrapper because it unloads all of the other scenes let's keep going here we want to run a while loop that's going to use that is done property to tell us when all of the async operations have actually finished and while we're in this Loop let's publish that progress report we can use the progress property there as the float value for that particular event I'm going to add just a little bit of delay here just cuz I don't want it going off too frequently but you know if you're working on something like this for your game adjust as necessary now let's figure out which one of the scenes in our scene group is actually marked as the active scene throw that into a variable then let's make sure that it's actually valid and if it is let's use the scene manager set active scene method then we're just about done just one more thing to do we've loaded all of the scenes so we have an event just for this let's publish it okay well we're actually almost finished here so let's finish off our unload scene method it's actually basically the inverse of what we just looked at with a few little extra things first of all I'm going to create a list so I can keep track of which scenes I actually want to unload it would also be helpful to keep track of which scene is actually active right now let's also figure out how many scenes are actually open now we can start iterating over all of these scenes and dealing with them so we can use I as our index and get the scene at that particular value of I let's a make sure that it's actually been loaded and not just sitting there unloaded because then there's nothing to do right we could just continue if it wasn't loaded next I want to make sure that if it's a certain scene like my bootstrapper or my active scene I don't want to unload it now this is a personal choice for my game the way that I want to set it up I would probably always leave the bootstrapper there and that's because I'm going to use that scene to store all kinds of things I want to make sure are persistent so here I'll say if it is the active scene or it is the bootstrapper let's just carry on otherwise I want to add it to this scenes list so that I can unload it now like we did before we can create a async operation group let's create an operation for each one of these scenes it's going to unload it asynchronously and then we'll add each of the operations into the group and after we've added the operation let's publish a message saying that we've started unloading the scene now similar to what we did with the loading of the scenes let's just have a while loop that will run until all of these operations are finished this time I'm not actually going to publish a progress report because I'm not going to show a bar when I'm unloading scenes now finally as an optional idea we could actually unload unused assets this is going to walk the hierarchy tree and figure out what's been used and if if it hasn't been used it's going to unload it and this is a little bit of an expensive operation it also returns an async operation so you could put it with the other jobs some people don't like using this method because a it gives you zero control and B you might have loaded up things that you haven't used yet but you're planning to use in the future and this might accidentally unload them on you next let's build a class that we can actually use in the editor so it'll be a monob behavior we'll call it scene loader this will handle showing a bar and a loading screen but this will also let us Define some scene groups right in the editor let's start with some serialized Fields I need a reference to the image I'm going to use for the loading bar and how fast I want it to fill up I also need references to the canvas and the camera because I'm going to turn them on and off when I'm loading a scene or rather a scene group Next let's actually have an array of scene groups exposed to the editor I need a few other helpers one is going to be the target progress the progress that we aiming for the bar to achieve her convenience let's also have a Boolean that says whether or not we're actually loading or not and then of course we need the PowerHouse that's going to do all the heavy lifting so let's have an instance of the scene group manager next let's have a start method since we don't actually have a main menu yet to create new games or load games let's just load the first scene group right in our start method the load scene group doesn't have to be too complicated we really just want to wrap up the manager method and decide whether or not we're going to show the loading screen now some people like to load in a whole other loading scene and that's one way you can do it but we can also just show the bar here let's say that at this point we want our Target progress to be a full bar so 1 F but we'll start the fill amount at zero now for a sanity check let's make sure there was a valid number passed in there after this we need an instance of that loading progress class that implements the I progress interface I'm going to add a lamb expression to the progress's progressed event and all this is going to do is say Target progress is going to equal the greater of either what's coming out of the event from the actual loading progress or or our Target progress now in this instance I've always set it to one so it will always be one but if you started your target progress at maybe a quarter of the bar or something as things progress it would let you move the bar like keep it moving forward as it were instead of always heading to the max I'm just going to add a little helper method here that will allow us to turn on and off the camera and the canvas when we're not loading and also just set that is loading flag then all we really have to do up in the method is enable the canvas then we can call the method in the manager passing in our particular scene group and our progress object and when that's done we can just turn the canvas and Camera back off if we come back up to the top we can create an update method that will handle actually progressing our bar if you don't have too many scenes to load it might actually look a little bit chunky so what we can do is smooth things out a little bit but first of all if we're not loading let's just get out of update we don't need to do anything here but let's grab the current fill amount and let's try to make this a little bit smoother so let's figure out the progress difference what's the absolute difference between what where we're filled now and where we want to be and then let's take that and multiply it by how fast we actually want to be filling up the bar now this value might need to be adjusted a little bit but I set it at 0. five now the loading bar fill amount will be a lured value between where we are where we want to be and this fill speed time time. Delta time this approach will keep the bar moving fairly consistently but it will slow down as it gets closer to the end if it's not quite finished one more thing before we leave this class I'm going to create an awake method and just register to each of the events that was in the manager just so that we can see clearly in the console that something was fired we can get rid of these later on just one more class to write the bootstrapper the bootstrapper is very simple all I want it to do is before any scene loads I want it to run an initialization method that method all it's going to do is load the bootstrapper scene which actually contains this class and quite a few of other classes so whatever's going on in the bootstrapper scene it's going to unload every other scene because it's load scene mode single and it'll just Exist by itself and run its startup logic and of course any other class in that scene is also going to start up so if we jump back into Unity you'll see that I've got the bootstrapper scene open there's a bootstrapper game object with that class we just looked at there's also the scene loader that has the scene loader script and you'll see I've just set up a very simple canvas with an image with a fill amount we can slide that back and forth you can see how it's going to look like there and of course a little bit of text and a background but that's really it however if we look over at the scene loader in the inspector now you can see that we can have an array of scene groups so let's make one I'm just going to start dragging in scenes from my project folder and assigning a different type to these for my first level I'm going to have gameplay a UI and a cinematic which I've disabled for right now but we still load up all three of those scenes but if I make another one here I can still have my gameplay but it's going to get ignored because that's the active scene and that's how I've set things up it would be valuable to leave it though in case you started the game on level two then I'll also have the normal UI we could have a different cinematic and then also maybe an additional environment and you can see that my new scene that I just dragged in there is lit up red that's a feature of the scene reference type it'll light up red because that scene is not included in my build settings well why don't we click play and see what happens okay so the bar moved up a little bit but it went awfully quick and that's because the scenes are all very small but if we look in the console there we can see it got the bootstrapper then it loaded up gameplay UI cinematics and published an event saying that all the scenes were loaded it might be more useful for our testing purposes to actually come back here into the scene group manager and just add a little DeLay So for every single scene that we're going to load let's just add a 2.5 second delay let's put a note here to myself to take this out later but it'll give us a better idea of what it would be like to load bigger scenes so if I come back in here now and press play Let's see what happens so there we go going a little bit longer we can see the things coming in and the bar is going slower and slower as it gets to the end and then here we are all scenes are done shows up my inventory which I can put away and now I can run around in my Game World and if you look up in the hierarchy you'll see that they're they're in the order they were loaded in as well the gameplay scene is marked in bold that means that it's the active scene where everything's going to get instantiated if we look at the scene loader here you'll see that I put two buttons on it and this is just for convenience for now for me to load up the second group or the first group so I'm going to load up the second group now and let's see what happens so there we go it's basically everything that was in the first group but I've added the extra environment there so now I can just run up there and continue my adventure if I so desire at this point I would start thinking about how am I going to start communicating between these different scenes and getting references to objects and systems in these other scenes for example my inventory is in the UI scene how am I going to do anything with it from the gameplay scene for me personally I've started to use the service locator more and more and the event bust in almost every project so there's a video on each of those topics already on the channel I encourage you to watch those if you're interested in that kind of thing I want to point out too that this kind of system lends itself very well to addressables and we're going to have a video on that topic very soon well that's all I've got for you today feel free to leave a comment or question below or join the other subscribers on Discord I've got a big episode planned for next week but if you can't wait that long just click on one of these boxes on your screen and I'll see you there

Channel: git-amend

Views: 5,713

Keywords: unity tutorial, unity arcade game, unity game tutorial, unity, game development, game dev, game development unity, programming, c#, software development, learn to code, learn programming, unity tutorials, unity devlog, indiedev, gamedev, unity3d

Id: JFP-cCFID7o

Length: 16min 58sec (1018 seconds)

Published: Sun Mar 03 2024