UE5 Understanding hard and soft references - Be a better game dev

[Music] welcome to an episode of being a better Game Dev so in this episode we are going to be checking out things like hard references soft references we're going to be talking about what they are how they function we're going to be checking out how the memory footprint of our different assets are affected by these things we're going to be checking out how references hang together and how pointing at different objects cause a cascading effect if we have hard references and how we can make use of soft references to avoid this we're also going to be checking out some different things like interfaces and components talking about it a little bit and see how we can use that to offset a few of the disadvantages of these things as well so stick around and check it out welcome back so in this video we're going to be talking a bit about hard references and soft references what they mean what's good and bad about them H how they work and also some workarounds to to avoid the the worst offenders so um starting off in this is a third person template project uh so it's just a third person character that's running around uh when we start and I have done a few things in this project I have added a asset in this case I've added a helicopter from from the Vigilante asset set it's available for free on the marketplace if that's something that you want um I have added a little bit of code to our third person character not a whole lot we'll go through it once it's relevant we have added some code inside of our level also very small amounts and I'll go through that when it becomes relevant as well um but starting off what what does it mean to have hard and soft references well if you take a uh blueprint for example or any asset in Unreal Engine you can go and check the reference viewer the reference viewer gives you this or a very similar view uh what this means is uh this is the blueprint in this case that we opened up and all the things to the right over here are assets that uh are being used by this blueprint all the assets to the left are are things that make use of this uh character in this case so everything on the right is dependencies for the character and everything on the left is something that has a dependency of the character uh so uh how this works is each of these lines represent a a um a dependency in the form of some kind of reference in the case here we have white uh lines and these are hard references so a hard reference means that Unreal Engine when it loads in a blueprint third person character in this case it loads up all its hard reference dependencies and loads them into memory so that it can access them whenever they're needed in runtime um this will show up for example if you go to uh let's go to our content folder and we go and right click on it and we say size map our size map here in this case consists of 208 megabytes of memory taken and of these 208 megabytes you can see what the different aspects of this character uh the memory is being used for so we can see that our skeletal mesh is here and it it uses 2.7 megabytes and it consists of these boxes that are consisting inside of it etc etc so we we have a few different boxes here that represent the different usages for our character in this case um now when we have a reference in our character so if we were to go to our character and let's say we create a new variable so remember in our size map we had 28 megabytes if we have another uh variable here and we make sure to choose BP West which is the the helicopter in this case and I say I want to have an object reference or a class reference these are both hard references so if I click one of these and I compile and I save and I go back to our content browser and I check size map you can see now that it's going to be 392 mbes so just by having that reference in our character it now says to on engine that this is something I have a hard reference to this is something I need to keep track of so you need to load this into memory as well when I get loaded into memory and if we go to our reference viewer you can see here that we have these assets over here that we're depending on or that we are yeah dependent on these are the ones that we load in and in the bottom here we have our context for default if we were to refresh this now you can see that below that context we get now our helicopter so now we have a hard reference to that other blueprint and this is in our third person character so what this means is when we open up this map or when this game mode gets launched H either of those say that they have a reference to this character which will then load in the character and all its dependencies which means all of these things and that in case in this case means that we load in this helicopter as well and if we double click into that we can see that it has a set of dependencies as well that it needs to make use of right and you can also set the search reference depth here to something higher so if we were to do three or something like that no apparently not this the dependency depth I guess it's taking a little bit um this might be a little bit bloated for us to actually uh get a good overview of but essentially here you can see how this tree sort of uh grows with each level so there are probably further dependencies here that are all loaded in once this blueprint character is loaded in uh so so it's easy to see I hope that if you have hard references to a lot of different objects H you will be loading in a lot of different things a lot of different assets and note that this is my third person character and my third person character is inside of this map but despite the helicopter not being here it will still be loaded into memory so it's completely unnecessary in this case right so we're using up a lot of memory for no reason in this case so we're going to be uh removing that helicopter for now like that now hopefully you have a basic understanding of of hard references and how it sort of works let's take a look a little bit at soft references so if we go into our third person character and we go in and create a variable and we call it helicopter inside of here we can choose to have the type actor and of these we have the two hard reference versions up here object and class we have to have two soft object references in the form of a soft object soft object reference and a soft class reference so if we wanted to spawn in a a another blueprint in the world another class we could take the soft class reference uh in our type we can have actor but then as a soft object reference type class we can choose to have for example our helicopter so this means that it will take the footprint of an actor but it can reference a West helicopter in this case so if we go and check our uh character uh let's see we go over here blueprints we can see that our size map is the same it's 208 still it hasn't been affected by this because it's just loading another actor and it only it already knows about actors because we are an actor uh using this reference now we could spawn it into the world but we can't spawn it in just straight up because if we do this and we say uh spawn actor from CLA it's going to be running a conversion from our soft reference to this uh but this being a soft reference means it's not loaded into the world so we have to manually tell it when to do so which means that when we press here for example on our press 2 key we can say asynchronous load um assets class asset like so this means that we will now tell it at this point here to load in this asset so it won't take up memory until we reach this point it will however be of the base type object class instead of an actor which is needed for spawning an actor so we can't just hook it up like so so we could either cast it to an actor and then hook it up over here uh but and of course we would have to do the okay this is not what it wanted I meant to do this cast actor like so no cast actor close there we go and if we hook it up like so it we would be able to uh spawn it into the world the asynchronous means it's going to be loading and be done at some point which means that we have two execution pins here we have one pin for when it's starting and when for one is completed so in this case I would want to hook up to the completed one to say that okay once we have loaded into memory then we want to spawn the actor so if we were to go to our map here and press the two key and then I eject from here I can see that the helicopter is over here so we focus on it and here we can see the helicopter so we're spawning it into the world now properly and everything is fine but our third person character is still going to have the the memory footprint of 208 megabytes like when we started the reference viewer now is going to be a little bit different if we refresh the reference viewer we're going to be seeing here now that we have our helicopter here like before but we now have a pink purple kind of a line instead of a white so this means that we have a a soft reference to this object so it's not necessarily needed to be loaded in once this asset is loaded into memory okay uh you you could also instead of just casting this actor you could just hook it up like so and this would work as well uh because this conversion is similar to the cast essentially so if we do this eject go here and focus on it so you can see the helicopter here is being spawned okay all is good and fine so far I hope so with a soft reference like this we won't take up as much memory uh and we will have a different uh relationship when comes to the reference viewer in what kind of assets will be needed to load in but we have the detriment of we need to choose when to actually load an asset in when we feel it's going to be needed and of course this means that we might need a little bit of time to do this depending on what kind of asset we load in so that might be something that you want to consider as well um the the differences between a soft and hard reference when it comes to accessing them is that a hard reference is going to be faster uh because it already has loaded it into memory so it's available a soft reference if you make use of it needs to first check and see if it exists before it actually can access the the object that it's referring to uh but but of course you have the memory as a offset for for that benefit then so the the speed over the memory and how do you combat this kind of situation uh other than using soft references how do you avoid uh hard references like this well let's take a look at the code that I have prepared so in our level we have if we go and open up our level blueprint here's our level blueprint uh we we're getting the third person character we're calling two events on it event one and two these are the ones that we see up here and they take in an actor as an input in our map currently we do not have an actor referenced here but let's say that we had our helicopter in the world here or this could be some other asset of course as well so if we go to our third person map here we can say that we want to create a reference to the helicopter and we say that we want to send that as an input to our events um what's happening here now is that in our third person character we're getting these events sent to us when we press the key and we get an actor here and let's say we wanted to do something with the helicopter in the helicopter we have a little bit of code we have an event that says helicopter event and we have an interface called helicopter interface event when the event is called the helicopter event we print out that the helicopter event has been triggered when the interface gets called we call in this event and say the same thing essentially so if we were to go to our character now compile save and go here and check the memory map we can see that it's still at 208 but the moment we say okay we want to make this a cost to BP West so that we are able to make use of the helicopter event helicopter event there we go so now if I were to go in here and play I press one we can see that the helicopter event is triggered is printed up in the the top left over there uh but now that we have had added this cast to our class that means that we have now created our hard reference so if we go to reference viewer we can see that it's back here with a white uh line and it's again going to be taking up memory for us for our character because we're forcing it to be loaded in now so this way causes us to create a hard reference and even if we didn't have this helicopter in the level just the existence of this cast would say that this blue print this third person character needs to have this helicopter loaded into memory to be able to function because we have this cost it's a hard reference if we remove this and instead say we want to call on the helicopter let's see here helicopter interface event so this one is calling on an actor saying we want to call the helicopter interface event and since it is an interface it will work if it has the interface if it does not have the interface it will do nothing uh the interface itself will again if we go in here and I press one you can see that the helicopter event is being triggered because we are calling the helicopter interface event which is calling the helicopter event which is calling the print string now if we go to our reference viewer refresh our character can see we have a soft reference to our helicopter which is of course from our helicopter over here if we were to remove this compile and save refresh our reference can see that we don't have a a a um dependency to anything except for our BPI here and that one is just being used by helicopter it's not actually a reference or a dependency for the helicopter so this this way we don't load in the helicopter at all we don't have a hard reference to it we don't have a soft reference to it we still able to uh access the code in it and if we check the memory we can see that our size map is 208 as well so an interface is one way to circumvent having hard references and avoid uh both the the hard reference um dependencies and also the memory footprint of your classes you could also do things with uh things like components and stuff and offload things that way uh I won't be showing that off in this tutorial however anyway uh that is hopefully understandable and it's the the sort of core concept of of hard and soft references um so the benefit of hard references again you're going to be having faster access time T because you always have the object available for you when you run um the payment for it is that you have to load everything into memory and that could be easily getting out of hand if you have a a lot of reference in because again if you have your reference viewer here you have let's do it like this we do a now let's do the cost we do a cost DP helicopter no not where helicopter there we go so in this case here we have the cost which means that we have a hard reference which means that it it is available here and if this helicopter in turn had a cost to let's say another helicopter then that helicopter would be loaded in and let's say that helicopter had I don't know a missile or something loaded as a direct reference the tree just expands and explodes if you don't keep track of how you're making use of your different references so that's why it's easy that the memory consumption can just get out of hand when when doing this so the soft references are of course a better choice when you're having certain objects that you don't need to have available at all times so it sort of depends on what kind of object that you're working with some things you will know that you always have reference uh a a need for and then having a direct reference a hard reference is is fine of course because you're going to be needing to access it at at all points or at any point so the soft references allows us to have a a smaller memory footprint uh it comes at the cost of being a little bit more finicky to work with since you need to make sure that you actually load it into memory before you spawn it into the world or interact with it anyway and such and uh you have some options of circumventing hard references as well using things like interfaces and components and such as well so that's going to be all for now keep on learning take care a big thank you to all of you who like comment subscribe and share my videos or through other means support this channel you are what makes this channel grow and become a resource for other people to learn from

Channel: LeafBranchGames

Views: 30,412

Keywords: learning hub, unreal engine, tutorial, unreal engine 5, blueprints, game design, game dev, unreal engine 5 tutorial, unreal engine 5 beginner tutorial, ue5 beginner tutorial, building user interfaces for unreal, engine ui design, user interface, design ui, design tutorial, building user interfaces, unreal engine user interface, Leafbranchgames, Good habits, Best practice, How to build menus and UI for Unreal engine 5, the right way, UE4, UE5, Reuse, Recycle, be a better game dev

Id: aUG54KCP89M

Length: 19min 57sec (1197 seconds)

Published: Mon Dec 11 2023