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‫Hello and welcome back.

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‫Now we have movement for the --, but we're not rotating that top part of the --, which we're calling

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‫the turret.

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‫So we'd like to be able to do that using our mouse.

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‫Now, take a look at what's going on here.

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‫As I'm moving my mouse cursor around in the world, I'm getting this red sphere.

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‫This is a debug sphere that I'm drawing in 3D space.

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‫Now notice as I move up against a wall, that sphere moves against the surface of the wall.

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‫So wherever my mouse cursor is moving, I'm getting this fear that corresponds to whatever object I'm

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‫hitting based on my cursor location.

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‫And this is going to be useful for us so we can have a location in space that we can rotate our turret

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‫towards.

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‫Now, in order to do this, there are some functions we need on the controller, so we have to access

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‫those functions on the controller.

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‫And in this video we're going to work on setting that up and we're also going to discuss how this is

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‫going to involve a concept known as casting.

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‫Now, the reason we want the controller is because there are functions on the controller that allow

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‫us to get the hit result under the cursor.

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‫Now we're talking about the mouse cursor.

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‫So say this is our screen and here's our mouse cursor.

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‫And the point at the tip of the cursor corresponds to a location on the screen.

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‫Now if we move the cursor around, our goal is that the turret part of our tank, that top part of our

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‫mesh is going to rotate so that it's facing the direction of that cursor.

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‫Now if we move the cursor around, there's a function on the controller that we can use to get the location

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‫corresponding to that cursor.

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‫If we were to draw a line straight out from the camera towards the cursor and hit some object in the

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‫world, we can get that location and use that location to set the rotation for the tank turret.

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‫Let me show you what I mean.

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‫Now, in order to get this hit location corresponding to our cursor, we need to use the controller.

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‫Now, let's talk about the controller for a brief moment.

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‫Let's say we have our pawn in the world.

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‫A pawn will have a controller.

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‫This is an invisible object that's associated with the pawn.

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‫Now, for our pawn, our controller is going to have the type A player controller and at the beginning

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‫of the game, the controller will possess the pawn.

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‫This is why we can see from the point of view of the camera that belongs to our pawn tank.

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‫Now we can access this controller.

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‫Our tank class inherits a function called Get Controller.

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‫It's inherited from the -- class.

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‫So what we'd like to do is get a hold of that controller and store that in a variable so that we can

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‫use it to access the function we need to get the hit result under the cursor.

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‫So let's set ourselves up for that.

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‫Now I'm here in the tank class and the place we need to access our controller is begin play.

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‫If we do it in the constructor, that's too early and we may not have a valid controller just yet.

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‫So we're going to need the begin play function here in the tank class.

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‫Now we have it here in the base pong class and so far we're not really using begin play in the base

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‫pong class.

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‫So what I'd like to do is move it over to the tank class.

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‫So I'm going to highlight begin play, including the comment and the protected section here and I'm

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‫simply going to cut it.

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‫And then back in tank stage, I'm going to paste it.

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‫Let's add this protected section here just above the private section with begin play inside.

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‫Now we've removed Begin Play from base pawn.

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‫We no longer have it here, but we also need to remove it from base pond cpp.

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‫Here it is.

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‫We can go ahead and delete it here and now we have it declared here in Tank H, but we also need to

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‫define it in tank CPP.

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‫So I'm going to define the function just under setup player input component.

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‫So it's going to be void begin play with no input parameters.

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‫There's the function body and we also need a tank pre fixing the function name.

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‫Now we know it's important to call super big in play.

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‫So that way any functionality in the begin play function and any of the parent classes will be still

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‫called.

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‫So here we have begin play.

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‫This is where we can get our controller and store it in a variable.

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‫So let's go back to Tank H and create a variable.

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‫Now this is going to be private and I'm going to stick it down here at the bottom of the private section

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‫and it's going to be a player controller pointer type and we can call this player controller ref.

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‫This will be our reference to the player controller.

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‫Now we're not talking about a C++ reference.

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‫This is still just a pointer, but we're going to use this to refer to the player controller.

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‫So now we have a player controller ref variable of type A player controller and we're ready to store

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‫the controller in this pointer.

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‫So let's go back to Tank Dot CP here and begin play and attempt to do this.

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‫So.

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‫What I'm going to do is say player, controller, ref equals and I'm going to attempt to call get controller.

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‫Now get controller, as I mentioned is on the -- class.

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‫Lets right click and go to definition and notice that this function returns an A controller.

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‫Now our variable is of type A player controller, not a controller.

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‫So what we're attempting to do here is take the return value from get controller, which is of a controller

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‫pointer type and we're trying to store it in an A player controller pointer.

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‫Notice we see the red squiggly here.

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‫It says a value of type.

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‫A controller pointer cannot be assigned to an entity of type.

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‫A player controller.

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‫We're getting an error.

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‫Let's take a look here at the documentation for a controller.

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‫Take a look.

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‫Here's a controller.

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‫And it says inheritance, hierarchy.

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‫And below a controller we see a a controller and a player controller.

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‫This means a player controller is a child class of a controller.

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‫Now, in C++, we cannot have a pointer of type.

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‫A player controller store the value of the address of an A controller.

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‫A controller is the parent type.

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‫A player controller is the child type.

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‫You cannot take an object of parent type and store it in a pointer of child type.

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‫So how do we get around this?

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‫So here's our problem.

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‫The get controller function returns the address of an A controller.

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‫Now, this is something we could store in an A controller pointer, but we can't store it in an A player

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‫controller pointer.

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‫The funny thing is, though, that the object returned by get controller is in fact a player controller.

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‫So we have this address in the form of an A controller pointer and we know it's stores a player controller,

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‫but if we have it in the form of an A controller, we cannot access the function that we need because

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‫it exists on a player controller.

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‫The function is called get hit result under cursor.

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‫Now if we have a value of type A controller pointer and we attempt to get that function that exists

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‫on a player controller, we will fail to do so.

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‫We'll get a compilation error.

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‫So since we know the object itself is a player controller, it's just stored in an A controller pointer.

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‫How do we get around this problem?

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‫The answer is we have to cast.

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‫We know that a controller is the parent class and a player controller is the child class.

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‫And we know that we cannot have an A controller stored in an A player controller pointer.

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‫We know we can go the other way around and have an A controller pointer store, an object of a player

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‫controller.

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‫That's in fact what we're seeing when we call get controller, it returns an A controller pointer that

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‫points to an A player controller.

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‫So if we have a value of type A controller pointer, we can use a special function called a cast to

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‫convert the type of the pointer to an A player controller pointer.

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‫So casting changes the type of one pointer to another pointer type as long as the object itself is the

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‫type that we're trying to cast to.

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‫Now, if we attempted to cast to an invalid type, for example, we have an A controller pointer pointing

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‫to a player controller object.

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‫If we attempt to cast to say, a character, the cast function returns null and we say that we fail

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‫the cast.

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‫So the cast function looks like this.

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‫It's a template just like create default sub object.

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‫This template function will adapt to the type chosen and in this function, the type we pass in is the

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‫type we're casting too.

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‫So we pass that type.

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‫We'd like to cast two inside the angle brackets and we pass the pointer that we'd like to cast into

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‫the parentheses.

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‫Here's an example.

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‫Let's say we'd like to cast to a player controller and a pointer of type A controller type.

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‫We pass the pointer into the parentheses and the type we're casting to in the angled brackets.

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‫And what gets returned is a value of type A player controller pointer.

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‫So here's the function call where we're passing the type in the angle brackets and the A controller

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‫pointer value that we get returned from get controller can go in the parentheses.

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‫So we need to cast this value that we're getting returned from get controller.

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‫That's going to be your challenge.

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‫So in Begin Play, use the get controller function and pass that value in to the cast function and cast

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‫to a player controller.

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‫And then you can store the result in our player controller ref pointer, which is of type A player controller

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‫pointer.

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‫Pause the video and perform the cast.

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‫Okay.

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‫So we've almost got all the work done here we just need to cast.

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‫So what we're going to do is call the cast function, which has angle brackets as well as parentheses.

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‫And what goes in the parentheses is the value that we'd like to cast.

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‫Now get controller returns a pointer of Type A controller.

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‫I'm going to move that right here into the parentheses.

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‫And the type we're casting to is a player controller.

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‫So again we're taking the value returned by get comptroller.

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‫This returns an a comptroller pointer or an address.

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‫Then we're using cast to cast it to an A player controller.

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‫We know that the object returned by gate controller is an A player controller object stored in an A

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‫controller pointer.

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‫So after we've cast this, what gets returned is a pointer of type A player controller.

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‫So we're storing that in player controller ref.

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‫Now that we have access to the controller in the form of an A player controller pointer, we can access

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‫the function we need to get the trace hit result under the cursor.

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‫So in summary, we used get controller to gain access to the controller.

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‫We also use the cast function to cast from the type A controller pointer to type A player controller

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‫pointer.

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‫Now we can access the function we need, which is get hit results under cursor which exists on the A

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‫player controller class.

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‫So we'll start using this function in the next video.

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‫I'll see you soon.