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‫Hello and welcome.

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‫The subject of this lecture is going to be the take damage function of the actor and how we call it.

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‫Let's dive in and find out all about it.

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‫So in order for us to be able to deal damage to something, we need to actually have something which

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‫we can hit.

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‫So let's go to our content browser route and bring in one of the BP shooter characters.

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‫Because actually what happens is if you bring in a character into the scene, then automatically Unreal

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‫is going to make this character AI controlled and the ones that spawn at the player starts will be player

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‫controlled.

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‫So that's great.

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‫That's exactly the behavior we want.

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‫If I go ahead and hit alt p, you'll notice I'm actually in the wrong spawn point, so maybe I want

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‫to delete this second player start.

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‫If I hit alt p now we'll be in the right location.

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‫There is my enemy.

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‫I can shoot at the enemy.

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‫I get the hit effect.

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‫But obviously I'm not doing any damage.

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‫Not yet anyway.

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‫And doing damage is a two part process.

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‫The first part is sending the damage and the second part is receiving it.

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‫In this lecture, we're going to deal with sending damage to the player and the function calls involved

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‫with that.

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‫So the main one that we're going to be looking at is in the actor Dot H and we're looking for a function

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‫call called take damage.

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‫And you can see here there is this virtual function here.

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‫It returns a float.

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‫What it's returning is the actual damage applied to the actor, the actual amount that really got applied.

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‫And what goes in is the damage amount, a damage event, which gives us more information about that.

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‫The damage that happened, we have an instigator.

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‫So that's saying who was the controller responsible for causing this damage?

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‫And then the damage causer, which is what was the actor responsible?

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‫So in this case, it might be a gun.

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‫Or is it saying here the projectile that exploded, the rock that landed on you in this case, the gun

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‫that shot you, is going to be the actor that was responsible.

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‫So that's take damage in a nutshell.

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‫Most of that should be pretty straightforward for you to put together with the exception of this damage

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‫event struct.

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‫And that's a little bit more complicated.

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‫So let's have a look at this damage event structure and see what can what can we do?

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‫How is it going to be composed?

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‫How are we going to put this together?

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‫Now, it's not immediately obvious, but there are actually two subtypes for this damage event.

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‫In practice, you're not going to actually create an EF damage event, but rather you'd be creating

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‫an EF point damage event, or you would be creating an EF radial damage event.

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‫Those are the two main types of damage that exist in Unreal.

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‫You can create more different types of damage for your own custom stuff, like you might have a fire

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‫damage and with different parameters, but in that case, we're interested in the EF radial radial and

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‫point damage.

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‫So radial again would be something like a grenade going off, in which case you want to say, okay,

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‫where is what's the radius, what's the fall off?

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‫All of those kinds of things where as the point damage is, as it sounds much more appropriate for things

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‫like guns.

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‫So we're going to create an EF point damage event and we're going to go and look for the constructor,

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‫here's the constructor for it, and we can see what it's taking in.

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‫It's taking the damage amount again.

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‫So that's a bit of repetition there.

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‫We're having the hit result that caused this point damage to take place.

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‫Then we're having the in shot direction.

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‫Great.

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‫We've already calculated that.

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‫I was thinking a little bit ahead when we did that in the previous lecture and then this subclass of

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‫damage type.

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‫Now this can be used to pass more information so that actually, rather than creating a different damage

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‫event type, you'd probably create a different you damage type.

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‫So you might have a fire type or something like that in that case, because we don't need any kind of

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‫damage type.

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‫We're not doing fire damage or anything extra like that poison damage.

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‫Then what we're going to do is just pass in a null pointer here instead.

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‫So let's have a go at constructing one of these together and then I will let you call that take damage

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‫event.

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‫So the first thing to do is to paste in the type, we're going to call it the damage event and then

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‫we're going to construct it.

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‫So first of all, the damage amount, well, we don't have one of these for the gun yet.

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‫We don't have how much damage it does.

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‫So we can go ahead and create some information there.

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‫We've got a max range already.

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‫We want some more properties in here.

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‫It's going to be an edit anywhere, which is going to allow us to say float damage.

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‫How much damage do we do?

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‫I'm going to do a damage of ten and then we can use this over in the C++.

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‫So damage is what we're going to pass in as the first argument.

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‫The second one is that hit result?

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‫Well, fortunately, we've got the hit results called hit.

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‫Then the next thing is going to be the shot direction which we already calculated for our emitter at

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‫location.

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‫Then we're going to look at the subclass, which is just going to be a null pointer.

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‫Okay, so that is done.

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‫The next thing would just be to get hold of the actor that we're trying to damage.

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‫That's fairly straightforward from the hit you do.

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‫Hit dot get actor on here.

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‫But you will need to check that this isn't null because we don't want to end up with a null actor that

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‫we're trying to do damage on or we're going to end up crashing.

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‫So your challenge is going to be to call that take damage function check for the actor being null.

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‫First of all, we don't want a null actor and call take damage and see if you can get it to compile.

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‫Pause the video and have a go.

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‫Okay.

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‫Welcome back.

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‫So we've got our guest actor in here.

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‫I'm just going to call this I'm going to give this a little variable.

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‫So a actor pointer is going to be the hit actor and we're then going to go ahead and do an if statement

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‫in here, basically saying if the hit actor is not equal to a null pointer, then we're going to go

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‫ahead with this hit actor to call the take damage function on it.

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‫And we're going to do the damage amount in here is the first argument.

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‫What was the second one?

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‫I'm just going to navigate back to the take damage and have a little look.

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‫So the next one is the struct that we've put together this damage event.

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‫Let's put that in a second.

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‫Then we're going to have a look at the controller that created this.

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‫Well, that's our controller.

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‫The gun's controller is the one doing the damage.

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‫And then this is the instigator was the last parameter in our take damage.

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‫And we probably only want to construct this struct inside this if actor not equal to null pointer because

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‫it's not needed if we don't have an actor to apply this damage to.

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‫So let's go over and compile and see if this is going to work.

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‫So I got an error in my log.

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‫Let's see what's going on.

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‫Oh, I'm just missing a semicolon.

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‫Well, that's pretty easy.

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‫One to fix after the get actor there.

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‫Let's go and try again.

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‫Cool.

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‫Everything has compiled successfully and we can just go ahead and play and just check that shooting

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‫is going to not give us any null errors or try and crash the engine.

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‫Looks like it's okay.

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‫So we'll move on to the next lecture where we're going to try and receive the damage on this actor here

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‫that we have placed in the level.

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‫So you there.