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‫Hello and welcome.

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‫In this lecture, we're implementing moving platforms.

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‫We're actually going to make this platform move by understanding something called the game loop and

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‫how the tick function in C++ relates to it.

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‫Let's dive in and find out.

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‫So up until this point, we have been ignoring this function here, the tick function.

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‫We've been putting everything in begin play because that's what we've used before in Blueprint.

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‫But let's shed a little bit of light on this tick function.

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‫To understand tick, we need to understand the concept of a game loop, and this is how most game engines

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‫will build their engine.

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‫The way it works is that, first of all, the game engine will take the input from the player.

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‫So whatever's currently happening, whether the space bar is down or whether it's the W key, whether

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‫the mouse is just moved a little bit, whether a mouse button is down, all that stuff is going to be

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‫taken in by the game engine and processed.

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‫Then the next thing is that information will be used to update the game state.

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‫Maybe the player will move forward a little bit, maybe a ball will bounce, all that sort of stuff

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‫will be calculated and physics engines run and all that sort of great stuff that we've seen in our previous

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‫games.

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‫And then the third step is that the game engine will take the game state and say, okay, well, the

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‫player's here and the camera's here, the ball is over there, and it will render it to the display.

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‫It will turn it from a set of numbers into an image to display on your screen.

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‫Now, that image is called a frame, a frame being a single picture in a series of pictures that make

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‫up a video.

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‫Now, your computer may be able to render lots and lots of frames a second, or it might render fewer.

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‫But that is called the frame rate.

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‫How many frames per second can your computer go through the game loop?

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‫How often can it process input, update state and render it out?

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‫That is the frames per second and in unreal we use the tick function to help us do the middle step of

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‫the game loop to help us update the state of our game.

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‫It is a function that gets called every frame and exists in blueprint as well as an event.

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‫So you get the tick event and it basically allows you to do something to update your game every single

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‫frame.

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‫Now in our case, what we want to do with this is allow it to move our platform.

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‫So how could we do that?

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‫Well, if we take our set actor location and remove it from begin play and instead we update that location

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‫in tick, that's going to not do very much initially because we'll just be setting constantly updating

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‫our location to the same location.

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‫If we do set actor location, my vector and then semicolon, that's just every single frame, every

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‫single iteration through the game loop.

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‫It's just going to put the actor in the same place.

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‫However, where this gets interesting is if we update the value inside of my vector.

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‫So what we can do is we could say my vector dot z is equal to my vector dot z plus one.

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‫So what we're doing here is we're taking the value that currently resides in my vector Z.

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‫We are adding one to it and then we are taking that whole result and putting it back into my vector

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‫dot z.

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‫So every single time we go through this game loop and tick is called by the unreal engine, my vector

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‫z should be increasing by one.

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‫So let's see what the result of this is.

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‫We go into Unreal and we hit the compile button and then we go ahead and hit play.

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‫We should see that that platform is rising up, floating up into the air because I'm increasing its

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‫Z location, so I'm making it go higher and higher.

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‫So I'd like you to have a go at changing Y instead of changing Z.

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‫So change the correct line of code.

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‫You may need to change some more than one place.

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‫Resize the platform cube so that it is a good platform for you to jump on and see if now updating Y

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‫instead of updating Z allows you to jump onto the platform, pause the video and have a go.

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‫Okay.

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‫Welcome back.

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‫So let's dive in to Visual Studio code.

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‫And what we want to do is be setting my vector y equal to my vector y plus one.

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‫So that's going to be moving it along the Y axis instead of the Z axis.

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‫And then we're going to be setting the location every frame to the result that is stored in the my vector

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‫variable.

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‫So we'll go back into Unreal and make sure we compile.

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‫Then we're going to search the outline for the moving platform and select it.

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‫Go to the details pane.

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‫And in here we want to basically well let's double click on the platform so we can see it and then we

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‫want to scale it up a little bit.

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‫So I'm going to use the scale tool with the R key and I'm going to increase the Y scale and the X scale

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‫and decrease the Z scale.

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‫So my platform is a little bit shorter.

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‫Like, so then we're going to might as well save the level hit play and the platform is floating off

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‫to my right.

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‫So it's also bigger, which means that I can come up and stand on it.

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‫And there we go.

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‫We've got our first little bit of a game mechanic.

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‫We've got a moving platform.

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‫It doesn't go backwards and forwards that we're going to figure out a little bit more about that in

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‫upcoming lectures.

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‫But for now, we've actually implemented some game functionality in C++.

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‫I think you should be very proud of yourself at this moment.

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‫Pat yourself on the back and I'll see you in the next lecture.