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‫Hello and welcome.

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‫In this lecture, we're going to be hooking up our health system to the animation blueprint so that

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‫I can shoot this character until he dies.

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‫Let's dive in and see how that works.

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‫So we want this boolean in the animation blueprint to be set automatically from our gameplay.

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‫And if we go through to our event graph and have a look how this is currently working, other properties

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‫like this, such as get velocity, get active, transform, we're going to the pawn and we're doing

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‫a get function on it every time we want to update our animation.

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‫So we want to kind of follow along in this model where we're going to go and get whether or not our

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‫player is dead.

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‫So to do that, we need to expose some functionality, some callable function from our C++.

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‫So let's go over to the C++ and have a look what is there.

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‫So we've could create a public function, but that doesn't necessarily make it accessible.

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‫To do the accessibility, we need to have a U function which makes it visible to blueprint and unrolls

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‫header tool system.

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‫But we've got to go one step further than just having it as a you function.

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‫So we start with the you function macro, but we want to make it blueprint callable.

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‫So that is the option that we can use blueprint callable.

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‫However, there is another option that overrides Blueprint or rather implies that it's blueprint callable

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‫and that is blueprint pure.

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‫Now we'll see the difference between blueprint pure and Blueprint callable in just a second.

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‫But just know that if you use Blueprint Pure, it is doing the same as Blueprint Callable and then some.

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‫So it's doing a little bit more than Blueprint callable.

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‫And then what we want is a function that returns Boolean that says whether or not this character is

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‫dead.

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‫That is going to be useful for us to know.

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‫And then finally, we want this to be a concert member function.

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‫Now, why does it want to be concert?

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‫Because when we call this function, we don't expect it to change any of the state of our shooter to

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‫character.

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‫So we can safely say that this should be a concert function.

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‫And in actual fact, concert and blueprint pure often go together because blueprint pure means that

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‫if we go over in to any blueprint, we can have a look at some pure nodes.

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‫This one here get act transform.

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‫That's a pure node.

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‫Get velocity is a pure node set speed is not a pure node.

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‫Can you see what might be linking these together?

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‫What about these makes this not pure and this one pure?

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‫Well, generally speaking, it's the fact that there's an execution pin.

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‫A pure node is one that doesn't have an execution pin.

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‫And it's usually safe to say that something doesn't have an execution pin when it doesn't have any impact

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‫on the thing that it's calling only on its result.

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‫Essentially, this means that no matter how many times we call this function, it's going to always

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‫output the same result.

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‫It's always going to have the same effect on the program.

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‫It's as a pure function.

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‫It doesn't change anything when it is called.

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‫So it's kind of the same as constant, although it's a little bit stronger because what it's saying

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‫is not just that it doesn't change anything here on the shooter character, but it doesn't change anything

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‫global, any state anywhere.

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‫Full stop.

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‫The only input, the only effect it has is in the outputs that it produces.

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‫So that's why we're choosing to make this blueprint pure.

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‫It removes the need for an execution pin, which makes it much nicer in blueprint.

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‫And it also just expresses the fact that we aren't making any changes to the state of our game when

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‫we call this function.

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‫So let's go ahead and try to create an implementation for this.

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‫In fact, I'm going to leave the implementation up to you as a challenge, and we're going to go over

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‫and hook this up in an anim graph, sorry, an event graph of the animation blueprint.

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‫So we're going to do this by having a new set here.

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‫We want to set the is dead boolean variable at the end and we want to get the pawn owner and we want

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‫to cast that because it needs to be a shooter character in order to have this is dead property.

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‫So we want to cast it to and in this case I want to cast it to the C++ shooter characters because I

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‫don't need to go all the way down to saying it's definitely a blueprint version of this because this

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‫new function actually exists on the C++ level.

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‫So we're going to go ahead and cast.

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‫If we succeed in cast, we're going to be setting the is dead property.

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‫And let me just put in some redirect nodes here to make our blueprint just a little bit nicer looking

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‫like so.

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‫And then what we want to do is using this shooter character reference.

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‫Now that we've cast it to a shooter character, we know that it should have this is dead property.

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‫So we should be able to do that.

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‫Once you've compiled and got it working, you can get this is dead property and set it here.

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‫This it's time for your challenge to calculate if we are dead or not.

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‫So return the correct boolean out of our is dead function.

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‫That's the first step.

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‫You might want to use some inequalities with our health variable for that and then hook up our variable.

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‫The dead is dead variable in the animation blueprint we got just short of doing that.

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‫We just needed we were just basically a compile away from getting that done.

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‫Pause the video and get that sorted.

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‫Okay.

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‫Welcome back.

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‫So let's go over to the code, first of all.

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‫So this fairly straightforwardly, I'm going to return an expression that returns a boolean.

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‫So we want to say, is the health less than or equal to zero, in which case we are indeed dead?

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‫That's about as simple as a an expression of function can get.

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‫So let's go ahead and build that.

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‫And once that has compiled, we can go over into Unreal and hook it up.

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‫So dragging off the as shooter to character, we are node we're going to have a shooter character reference

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‫here so we want to do is dead gives us this is dead function you can see it has no execution pin because

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‫it is pure.

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‫Then we take this boolean off of that and hook it up to our is dead variable.

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‫And now if we go ahead and play, we should actually be able to kill off that character in the world.

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‫We'll shoot at him until his health goes down to zero.

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‫And there you go.

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‫The animation has successfully killed him off.