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‫Hello and welcome.

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‫In this lecture we're going to be introducing member functions and this get safe and normal function

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‫that will allow us to get hold of the direction of a particular vector.

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‫Let's dive in and see how this works.

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‫So our simple method for sending the platform back in the opposite direction is working at the speeds

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‫we've tested it out at.

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‫But what happens if I say, Hey, let's make this platform go ten times faster?

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‫Let's go ahead and play and see what happens.

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‫Well, suddenly that platforms jump forward quite a lot and it's not hovering around the same location

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‫as it was before.

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‫And the reason for this is because the current location, when we set it as the start location, isn't

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‫necessarily exactly the distance moved, we could have overshot.

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‫And that is captured here in the if statement.

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‫We're saying that the distance moved is greater than the move distance, which means that we will have

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‫overshot.

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‫We have to have overshot in order to have triggered this if statement.

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‫But the question is by how much, and that's going to depend very much on how large the Delta time is.

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‫We can overshoot by quite large amounts, especially if the platform velocity is large, which means

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‫that our start location may drift over time.

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‫It may not stay constant.

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‫So the better way to do this would be to calculate how far we need to move from the original start location

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‫to get to the new one using the exact move distance.

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‫So let's try and visualize this back and forth calculation.

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‫We're saying we've got a platform at its start location over here.

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‫We say it's got a velocity which we can represent with an arrow that is a direction and a size, and

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‫it's also got a distance that we want it to move.

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‫We'll just represent it by this brace here.

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‫Now, what we're saying is we would like to figure out the exact point where the platform would be at

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‫the end, not overshot, but just exactly the end location.

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‫Now, the way we can do this is by taking the direction of that velocity arrow.

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‫So in vector parlance, this is called the normal of the arrow, and it basically takes it down to being

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‫of size one.

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‫So we get the direction but a size of one.

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‫So that allows us to know this count, essentially the size of the velocity, how fast we're going.

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‫And then what we can do is we can multiply that direction by the quantity of our distance to give us

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‫an arrow that gives us the whole movement from the start location right to the end location.

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‫Exactly.

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‫So let's have a look at how we can do this in C++.

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‫What we're looking for is a new start location.

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‫So let's remove how we're currently doing this and we're going to have a start location equal to, well,

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‫what is it going to be equal to?

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‫Well, it's going to be equal to, first of all, the start location plus something, because we're

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‫starting from here and we're adding this green vector to get to the end.

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‫So what's that green vector there?

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‫Well, that's where we need to get the normal of the platform velocity.

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‫And just to make it easier for us to understand, I'm going to split that into its own variable.

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‫So we're going to create a new variable of type F vector, which I am going to call the move direction,

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‫just to make it super clear what it is that we're trying to store in it and then we're going to get

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‫this from the platform velocity dot, get safe, normal and then some parentheses around the end.

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‫So what's going on here?

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‫We haven't seen this before.

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‫We've used Dot to get hold of the components of the vector, the X, Y and Z.

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‫Those were variables.

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‫But in C++ and in object oriented programming in general, we also have functions that exist on classes,

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‫so we can use the DOT operator to get hold of one of those.

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‫We've used the colon colon when we've been trying to get it out of the class itself.

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‫But when we want to do an operation with the actual vector itself, so platform velocities vector,

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‫we can use the dot operator to get the normal of that vector.

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‫So that's what we're doing here, using a member function instead of a member variable.

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‫So we've got the safe normal of that platform velocity and we'll put semicolon at the end of the line

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‫because here we've got a variable that's essentially we're saying that's the move direction.

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‫So now we can use that in the subsequent line to do a move direction multiplied by the move distance

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‫that's configured because we want to move exactly to the end, not overshoot.

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‫And then after we've done that, we should actually move our platform to the end location.

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‫So we're going to do a set actor location to be the start location, because otherwise our platform

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‫will have overshot and gone past that end location because we'll have updated it with the current location,

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‫which is the overshot location.

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‫So that allows us to move exactly to the end point.

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‫And then start from that new starting location.

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‫Now it's important that we update the platform velocity after we do all of this because we're using

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‫it to get hold of the move direction.

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‫So I'm going to update the platform velocity after we set the actor location.

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‫Now let's go back into one reel and hit compile and see if this is fixed.

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‫The problem with our platform moving backwards and forwards, let's close down this terminal and hit

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‫play.

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‫And now if we have a look, the platform is moving quickly, but it is moving reliably around the start

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‫and end location we would expect.

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‫So that's all I wanted to cover in this lecture.

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‫We just corrected a little bit of a bug that could have cropped up for some of our platform configurations.

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‫I'll see you in the next one.