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‫Hello and welcome.

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‫In this lecture, we're going to be looking at how we can add multiple components to an actor so that

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‫we can have multiple meshes and a more complicated actor that acts as a single unit when it comes to

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‫physics.

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‫Let's dive in and see how to do this.

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‫So now that we've got a decent looking level, let's look at putting together a little bit of a diorama

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‫for us to knock down.

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‫Now, you'll notice that when I dragged in this rack mesh, it created an actor but doesn't have any

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‫rack elements inside it.

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‫Now, you could go ahead to go over to the content draw and just cancel out the filter here by clicking

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‫on the filter button again and just hitting reset filters.

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‫Then going to the content folder, the industry props meshes and looking for the actual rack item itself.

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‫I can drag that into the scene, but you'll notice I would have to very carefully position this.

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‫And what happens if I enable physics on both of these items?

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‫If I go ahead and hit play, you see that they kind of work, they kind of stick together to each other

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‫because but but then if you hit them, this kind of weirdness happens because they aren't cemented together

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‫as one single item.

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‫So if we want to make a single item out of multiple of these, what we need to look at doing is having

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‫multiple components.

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‫So when you select either one of these actors, you'll notice that they are actors that contain a single

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‫component, a static mesh component.

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‫We've seen this before, but you can have more than one of these static mesh components.

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‫You can add actually as many of them as you like.

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‫One of them has to be at the root of the actor and the other ones will be children of it.

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‫And let's just have a look at what that means.

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‫If I, first of all, delete the rack actor that I brought into the scene, I'm going to open up my

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‫content drawer and instead of dragging on to the viewport, I'm going to have my rack.

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‫One selected the vertical blue bars and I'm going to select my rack two and drag it onto the static

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‫mesh component.

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‫And you can see it gets nested just underneath the first static mesh component.

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‫So that's what I mean by it is a child of that static mesh component.

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‫And what that means is that if we move the actor or the static mesh component, the rack will move with

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‫it.

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‫So the position of the rack, if you click on that rack component, you can see that the location is

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‫currently set to 000.

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‫But that's not true.

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‫It's not at 000 in the world.

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‫If I look at the rack, the rack says it's got a whole bunch of numbers, 1600 and even some offset

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‫from the ground.

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‫So why is this rack three within it showing something different?

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‫Well, that's because when you are a child of another component, your position is relative to the position

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‫of the parent.

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‫So if I were to move this component, if I select the Rack three component and I move it up along the

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‫rack, then you can see that the only change to the location is that Z movement that I've added, and

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‫that gets applied along with the position of the parent in order to give us the overall position of

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‫that component, which is very handy because it automatically means that whenever we move the parent

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‫around, the child is going to move with it.

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‫And by the way, exactly the same thing holds if I were to rotate the parent, it also rotates the child.

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‫If I were to scale the parent, it also scales the child.

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‫But let's undo the scaling and rotation for now because I'm quite happy with it as it is.

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‫So I'd like to challenge you to add another rack.

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‫The way we're going to do this is by adding a second child component to that actor.

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‫It's going to be a sibling of the first rack, but a child of those blue bars.

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‫And you need to enable physics on the root.

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‫So on the top most static mesh component and see what happens when you play.

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‫What happens now if we hit it with one of our ball bearings?

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‫Do we get any of that weird glitching?

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‫Okay.

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‫Welcome back.

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‫So I'm going to do this one of two ways, so you could drag it in from the content drawer, or you could

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‫select the rack component in the details pane and copy and paste it to get a second one.

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‫And you can see that these are now siblings.

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‫We've got a rack three and a rack four and we've got a route static mesh component.

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‫I keep calling this the route because the way this works with actors is that one of these components

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‫always has to be the root component, and it's actually the position of the route component that tells

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‫us the position of the actor.

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‫The actor doesn't have a separate position.

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‫It is only that position of the route component.

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‫So what we can do now is we can move this second rack up a little bit so that we've got a nice kind

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‫of layout here.

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‫And then what we can do is select that route static mesh component, select the physics category and

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‫make sure we've got simulate physics enabled, which we do already.

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‫At least I do.

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‫The other two racks should have it disabled, so the two children should have it disabled.

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‫And if you go ahead and hit play now and launch a cannonball at this rack with a good aim, you can

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‫see that the whole thing has now been welded together and it moves as a single unit, which is much

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‫more as we want it to be.

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‫Great stuff.

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‫That's it for this lecture and I will see you in the next one.