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‫Hello and welcome.

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‫In this lecture we are going to be covering lots of cool things, but most importantly, we're going

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‫to be looking at how we can child a actor to another actor.

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‫As you can see here, the rifle is a child of the shooter character and how we can make it such that

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‫the mesh there is actually attached to the hand of this skeletal mesh.

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‫As you can see, that gun is moving around with that player's hand.

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‫Let's dive in and see how it's done.

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‫So the first thing we want to do before putting our gun in the hands of this mesh is we want to remove

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‫or hide the gun that is currently there.

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‫Now, I find that the easiest way of doing this is to hide the bone that has the gun mesh.

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‫Let's have a look.

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‫So if we go over to the shooter character, BP would be a good entry point for this.

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‫And then I want to find go to the actual mesh here.

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‫We've got the skeletal mesh.

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‫And if I go to this skeleton, then we can find that this gun here, if I click on the gun, has got

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‫a bone leading up to it called the weapon.

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‫Bone and weapon underscore AR.

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‫And basically we want to hide this, but the easiest way to hide this across the board is going to be

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‫to do it in code and we're going to do it in C++.

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‫So the first thing is to get hold of the mesh component.

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‫The way to do this when you're on a character subclass is to call to get mesh cool.

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‫So we've got get mesh.

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‫Then with the mesh we want to hide the bone.

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‫There is handily a hide bone by name method and this actually exists on the parent of the skeletal mesh

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‫component, the skinned mesh component.

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‫Let's have a look at the header file briefly.

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‫Skinned mesh component.

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‫There is a couple of functions here.

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‫The one we're looking for is Hide Bone by name.

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‫So you can see the signature here.

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‫We've got the bone name comes in and f name.

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‫And then the second thing is this e fish body op.

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‫Now as far as I can tell, this isn't used in the code base, but we've got to provide it because it's

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‫there in the signature.

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‫So let's go ahead and use it.

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‫So Arrow going to do the hide bone by name.

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‫Unfortunately, my autocomplete is not working.

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‫That's a bug in 4.25 at the moment in V's code or to complete doesn't 100% want to work.

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‫But that's okay.

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‫We can learn to do it the manual way instead.

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‫Then we're going to want the name of the bone and I'll leave that up to you as an exercise to fill that

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‫out in a second.

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‫And then the second thing is we wanted that a phys op body thing and we're just going to go for that.

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‫That's an enum, so we're going to need to fill it out.

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‫I'm going to use F 12 to go to the definition and see what we have got.

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‫PBO None.

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‫Don't do anything that sounds like a sensible default.

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‫Let's go with that and then we'll use the semicolon to finish off our line right there.

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‫So let's compile this and see if we've got all the includes we need.

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‫Cool.

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‫Looks like it's working so we must have all the includes we need now.

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‫Let's what's your challenge is to put in the bone name give that a quick go mini challenge and we're

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‫coming back the bone name is weapon underscore R it was hinted at a little bit before weapon underscore

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‫R should do the trick.

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‫If we go ahead and recompile with that now and we hit play, you can see that he's no longer holding

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‫a gun.

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‫Fantastic.

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‫So the next thing is to put a different gun in his hand, the actor gun.

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‫So we need to go over to our skeleton.

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‫And what we want to do here is add in a new socket.

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‫So we're going to add in a socket in place of our weapon.

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‫R And what is a socket?

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‫A socket as it sounds like a plug socket is something that you can plug in.

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‫It's a point at which you can plug in other things.

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‫So you might want to be able to plug in, for example, a gun and you want it to be chided not to the

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‫mesh as a whole, but to a specific bone of that mesh, which means that it will move correctly with

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‫the character's arms.

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‫When he's doing an animation, when he's jogging around, it's going to look like it's attached to his

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‫hand rather than somewhere on it, not rigidly fixed to his torso.

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‫So we're going to add a child socket to a weapon.

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‫Do this.

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‫You go to the skeleton, you right click on the bone that you want to attach this socket to and you

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‫click add socket.

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‫And we're just going to call this one the weapon.

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‫Socket.

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‫I'm using camel case here as my convention, and that's what we're going to want to attach to.

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‫Now, you'll see where this comes in handy when we go to actually do the attachment for our gun.

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‫Now, the thing to note here is that we don't want to do a set up attachment as we would do in the constructor

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‫at runtime.

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‫When we do attachment, we have to use a different set of functions rather than the ones that we use

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‫in the constructor.

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‫And remember when I said that the only hierarchy here really is between scene components.

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‫Now, fortunately, we don't have to go in and get the root component of the gun and attach it.

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‫There is a helper method on the actor that allows us to do attachment and that is attached to component.

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‫So let's see where that's defined.

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‫If we go to look at the actor H header file and there's a couple of these, we want the one that lives

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‫under game framework and we're going to go and search in here for attach to component open brackets

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‫and find the actual declaration.

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‫Here it is.

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‫So what's this going to take in?

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‫It's going to take in a U.S. component, the parent that we want to attach to in this case, it's going

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‫to be our skeletal mesh of the character.

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‫The transform rules will get to this in just a second.

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‫And then there you go, the socket name, that's where on a skeletal mesh should we attach to?

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‫If it's a skeletal mesh, it'll attach to the socket.

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‫If it is not a skeletal mesh, it'll ignore the socket argument and just attach if it's a static mesh,

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‫for example.

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‫So we want to attach to get mesh.

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‫We have these transform rules.

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‫What are those?

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‫Let's click through F 12 to click through to their the different rules that are available.

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‫There's these are the preset rules.

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‫You can define your own, but you might as well use these preset ones.

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‫We've got keep relative transform, keep world transform snap to target not including scale will ignore

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‫these.

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‫Lastly, the main two to look out for are these first two and it basically means when we're attaching,

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‫should it stay the same place it was in the world, or should we use that world position as the new

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‫local position in our case?

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‫Because we want that gun to essentially be at zero zero, which would be its location in the world.

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‫We want to keep the relative transform, so let's do that.

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‫We're going to have the F transform rules keep relative transform.

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‫So I have transformed rooms rules colon colon and then should be let me see just copy over the keep

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‫relative transforms like so and then we want the socket.

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‫So again text macro here and then the socket name which was weapon socket.

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‫And finish off the line.

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‫That's going to set up the attachment.

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‫And now the final point is going to be to we want to set up.

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‫The gun to have this class as its owner.

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‫This is a bit of a subtle point.

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‫Why do we have an owner?

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‫I just said that there wasn't any hierarchy between actors.

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‫Well, there isn't in the sense of transforms, but they do have ownership.

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‫And where this ownership really comes into play is in multiplayer and in damage.

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‫So we'll see later on how we will need to know about the owner.

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‫It also allows the gun to know what is the owning character and it can use that to get references to

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‫the owning character later on.

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‫This will be useful.

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‫At the moment we don't particularly care, but we're just going to do it for completeness sake.

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‫Now actually name this wrong.

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‫It shouldn't be set up owner, but set owner to this because this is the actor that is the owner of

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‫the gun.

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‫Cool beans.

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‫Let's compile and see if this is working.

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‫The compiled successful.

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‫Let's dive in and play the game.

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‫Awesome.

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‫We have got a weapon in our hands.

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‫Is it in the right place?

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‫Let's have a look.

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‫Let's f eight out of here and have a look at the hand.

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‫Not quite.

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‫You can see that we could do a little bit of adjusting here.

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‫So that's what we're going to do.

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‫And this is a challenge for you.

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‫Basically, what you're going to try and do is find what the offsets should be on the mesh, such that

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‫this handle is actually inside our meshes Wraith character's hand.

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‫Pause the video and have a go at that.

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‫Okay.

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‫Welcome back.

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‫So I'm going to do this by selecting that mesh and trying to move it.

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‫I'm going to have to set the grid snap size in the viewport to a little bit less.

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‫And I'm going to try and zoom in as best I can on that hand.

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‫Okay.

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‫Bringing that down a little bit.

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‫I think that's good.

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‫Shout.

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‫Now let's go ahead and copy the location and open up.

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‫Go to the content browser and open up the BP rifle.

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‫Open the full blueprint editor, go to the mesh and stop simulating and paste the location that we had

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‫copied in there.

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‫Okay, cool.

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‫Copy that.

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‫And let's go and hit play.

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‫And let's see that it actually brought across the right thing.

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‫Fade out and zoom in.

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‫By the way, you can use the scroll wheel to slow down your movement when you're moving in this in this

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‫kind of way.

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‫Fantastic.

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‫Looks like he has got his hand directly on the handle.

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‫Awesome stuff.

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‫So we have learnt how we can child actors to other actors and how we can attach scene components to

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‫sockets of skeletal meshes.

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‫In the next lecture, we're going to be looking a little bit at shooting and how the this gun architecture

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‫basically dovetails into a shooting architecture.

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‫So I'll see you there.