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‫Hello and welcome.

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‫In this lecture, we're going to learn how to create classes that allow us to share configuration and

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‫functionality between multiple objects in our scene.

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‫Let's dive in and see how it works.

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‫Now the real power of programming with objects comes when we start to use classes and instances.

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‫Well, what is a class?

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‫Well, effectively it is a like a template or a blueprint in the regular sense of that word for objects.

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‫So this adventure here, we call this the adventurer class and it has some default data and it has some

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‫functionality, but we can go and create an instance of this class, such as adventure number one.

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‫We could call in Bob, for example, and he has his own copy of that data from the Adventurer class.

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‫This is the actual object and the class is something that we make the objects from.

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‫You can also then have an adventurer to a second instance of the same class and they share the functionality,

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‫notice they share all the same functionality and they can have their own version of the data.

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‫So you can see Adventurer two has changed his experience points.

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‫Now the benefit of this is twofold.

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‫One is that we're sharing all that functionality between these different objects, and second is that

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‫any of that data that we haven't changed such is the experience 500 or the level one.

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‫If I changed level one to level two, it would change it across all of the instances of the class as

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‫well.

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‫So how do we go and actually create something like this in Unreal?

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‫Well, the first thing I want to do is bring in something that's going to act as our projectile so the

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‫projectile can be our first object and class that we create.

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‫So I'm going to go to the quickly enter project button in the toolbar, go down to shapes and select

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‫sphere and drag a sphere into my scene.

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‫I'm also going to drag it up a little bit and I'm going to try and scale it, make it a little bit smaller

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‫by using the scale tool.

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‫And if I click here in the center on the White Bit, I can scale the whole thing uniformly till I've

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‫got something that's about the right size for my projectile.

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‫Now, what I want to do with this projectile is I want to turn it from just being a single object into

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‫being a blueprint class for multiple objects.

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‫There's an easy way that we can do this.

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‫Over in the details panel, there is a little blueprint button.

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‫If you click on that, you can see it says converts this actor into a reusable blueprint class that

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‫can have script behavior.

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‫So we can click on that and we just want to have this new subclass.

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‫We just leave the defaults as it is.

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‫The only thing we want to change is the name.

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‫Now what we want to call it is projectile, but there is a bit of a naming convention that we tend to

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‫use.

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‫It's not obligatory.

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‫It doesn't have any kind of functional impact on this project, but it does help us to understand things

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‫a little bit better.

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‫When we make a blueprint class, we tend to prefix it with BP in capital underscore, and that just

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‫allows us to instantly see what objects here are.

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‫Blueprint classes.

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‫We can go ahead and click select, which for some reason is effectively create and what it does, it

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‫goes ahead and opens up a new editor here, the editor for the Blueprint class itself.

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‫Now we can, like the other editors, dock this into the main window.

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‫And you can see again, we've got a lot of stuff.

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‫It's very similar to the level blueprint, but we've got a few other things such as a viewport in here

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‫that allows us to preview what this blueprint class would look like when we create an object instance

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‫of it.

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‫So now we've got this main class.

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‫We should be able to bring more instances and more objects of this class into the level.

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‫And indeed, we can.

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‫We could either duplicate the object that we've already got here, or you open up the content draw and

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‫right at the root of your content folder.

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‫If you select your content folder in the left hand pane, we've got a projectile blueprint.

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‫So what we can do is we can drag that into our scene and it will have created a new instance, a new

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‫copy of that blueprint.

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‫But like I said, these are linked copies.

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‫Making a change to a property in the BP projectile editor should change it for all instances.

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‫So the difference here is we've got a details pane over on the right.

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‫That's very much the same as the details pane we have in our level.

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‫Editor With the exception that you have to actually click on the components in the left hand pane to

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‫see their properties.

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‫So you may have to click down to static mesh components to see some of the properties we're used to

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‫seeing directly at the root actor level.

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‫So one thing to take note of how to do here is changing the material.

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‫So at the moment, this material on the ball is very white.

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‫We might want to change this to something.

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‫If you have this static mesh component selected over in the pane on the left and then go over to the

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‫details pane on the right, you can see that there's a section labeled Materials and Elements Zero.

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‫You can click the down arrow on this and you can see a list of all the materials we've got in our project,

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‫and you can select any of these and try them out.

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‫So I could try something like this cobblestone material.

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‫And you can see it looks a little bit ridiculous on our cannonball, so I am going to not use that one.

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‫So I'd like to challenge you to turn this projectile into a cannonball.

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‫Now, the way we're going to do this is, first of all, enabling physics.

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‫You will have to select the static mesh component to find the physics properties and then enable physics

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‫and choose a material of your liking that suits a cannonball a lot better than the current pebble one

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‫that I have selected.

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‫And then go back to your scene and have a look at what happens.

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‫What have they changed there or have they not?

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‫Pause, video and have a go.

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‫Okay.

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‫Welcome back.

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‫So, first of all, if I hit play, you'll notice that these two balls just sit there because physics

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‫isn't enabled.

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‫We're going to want physics enabled.

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‫So let's go to our details pane with the static mesh component selected over in the left hand pane.

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‫And we're going to scroll on down to where it has the physics section and checkbox for simulate physics.

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‫The other change I want to make here is I want to change the materials section and this is element zero.

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‫If you click on the dropdown now I'm going to look for a metallic one and I think I will go for the

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‫chrome metal material so I get a little chrome ball.

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‫Now, that's great.

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‫So it's not as boring looking as it was before.

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‫Now we can save if we want to, but it's not absolutely necessary.

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‫We can go ahead and hit play.

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‫And if we zoom out, you can see those balls are rolling around on the floor with physics enabled and

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‫with a new material, not just one of them, but both of them because they are linked back to this blueprint

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‫class and they are instances of it.

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‫So this is fantastic.

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‫We'll be able to use this for all sorts of things where we need multiple instances of the same class

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‫in our game and prevents us from having to repeat ourselves too many times.

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‫Great stuff.

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‫I'll see you in the next lecture.