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‫Hello and welcome.

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‫In this lecture, we are going to be sorting out the angle of our blind space, hooking that up to our

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‫gameplay.

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‫And in the process we're going to have to learn a lot of maths, a lot of transforms and vectors.

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‫So let's dive in and figure out how that works.

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‫So we want to be able to get the angle at which we should be moving.

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‫However, before we do that, we need to do a little bit of maths because we want to understand how

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‫we can get this angle which is local to the player.

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‫And I'll explain what I mean by local and global and how we can get that from a global velocity and

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‫what those terms mean anyway.

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‫So let's have a look.

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‫First of all, we need to have a bit of a basic primer on transforms and what transforms are we've seen

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‫them or you have seen them a little bit before.

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‫When you look at any of the scene components, that's these ones in the hierarchy.

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‫You can see they have a transform here.

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‫So location, rotation, scale properties, that's basically what a transform is.

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‫But one thing that you're not seeing here is that also part of this transform is the fact that these

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‫same components are in a hierarchy, meaning that their transformer also has a parent or, you know,

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‫basically hierarchical.

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‫So how does that work?

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‫Well, here's a kind of toy example.

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‫We've got the cube here which say is our base, it's the center of our world or something.

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‫So that's going to be our world space.

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‫We've got this character here, the little smiley face, and he's got a position in the world relative

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‫to his home base.

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‫And then this character has a gun and the gun has a position relative to the character.

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‫So the way this hierarchy works is that the parent of the gun is the character, the parent, or the

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‫character is his home base or the world.

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‫And then we have some local coordinate systems within these.

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‫So the worlds coordinate system is the, the world system, the global system.

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‫Then the coordinates of our character are then local to its position.

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‫So the gun is positioned relative to its character.

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‫What does that mean?

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‫That means that if the character decides to go off on a little escapade, then the gun moves with it,

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‫because the position of the gun relative to the character has remained the same, but because the character's

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‫moved, its position in the world has moved.

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‫Same happens with rotation.

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‫If the character turns around, the gun must turn around as well.

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‫That's how Transformers work essentially is also scaled, but we're not going to look at scale.

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‫It's the same, but it's just complicating things and we don't need to do.

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‫Have a look at that.

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‫It's not relevant to us.

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‫So let's have a look, a different look at this.

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‫We've got global space and local space.

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‫So the global space has the base at the center of the world and the character has gone off and to the

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‫right.

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‫The local space, on the other hand, sees things in the opposite light.

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‫It says that the character is the center of the world and that the base has gone over to the left has

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‫gone backwards.

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‫You know, that's the difference between global and local.

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‫It all depends on your point of view.

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‫Everything is relative.

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‫So this is what we mean when we talk about transforming between global and local space and which one

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‫are we interested in?

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‫For our angle, we're interested in a local angle relative to where the player is looking.

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‫We're saying, you know, are we moving over to the right?

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‫That's what we're saying that not globally, but locally.

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‫Are we moving to the right locally to our player?

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‫Because if our players turned around 180 degrees, he shouldn't play a left animation just because he

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‫turned around.

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‫So one more important distinction is how we do transformations for vectors of different sorts.

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‫The first example I want to look at is a position vector.

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‫So a position vector basically is a vector that gives us the difference between the current location

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‫or the zero point in our coordinate system, which when we are focused on the character, is the character

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‫himself, and then it gives us an arrow that points to where something should be.

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‫So in this case, it is the gun location vector.

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‫Now, if we transform this in to our world space, this is what happens.

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‫The arrow now points from the center of our new world, the global space, and it points to the gun.

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‫So that's what happens if you transform a position vector.

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‫Now, if you do a direction vector, things look a little bit different.

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‫A direction vector is one that says This is the way I should point, not necessarily where a thing is

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‫and this transforms rather differently because we now aren't interested in it pointing to the same location.

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‫So that position doesn't really get updated.

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‫Instead it get the a vector gets rotated and scaled or whatever it is and we end up with it looking

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‫a little bit like this.

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‫So that's actually the kind of transforming.

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‫Nation that we want to be doing because we're dealing with a velocity which is a direction vector rather

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‫than a position vector or velocity doesn't tell us anything about where we should be.

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‫It tells us about what direction we should be going in and how fast we should be going in that direction.

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‫So with that theory out of the way, let's go ahead and calculate our direction from this velocity.

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‫So we know that velocity is in global space and we want to convert it to local space.

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‫Now that means that generally speaking, we're always trying to do things the other way round, usually

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‫because we're saying, well, we've got the position, the local position of a gun, it's local transform.

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‫We want to figure out what it is in world space so that we can render it relative to everything else.

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‫Now, that's not what we're trying to do here.

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‫We're trying to do the opposite.

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‫So what we actually want is called an inverse transform.

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‫The transform goes this way from local to global.

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‫The inverse transform goes from global to local.

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‫So because we've got this global velocity, we want to inverse transform.

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‫So let's take off here and look for inverse transform.

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‫And you can see that we've got these two options.

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‫We don't care about these matrix ones.

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‫We've got the two options of for direction and location.

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‫And as I said, the difference is that a location will move that position around.

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‫The direction is just going to apply the rotation and scale.

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‫So we want the direction.

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‫We need a transform to rotate it by.

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‫We're going to have to get that transform of the pawn itself, of the character.

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‫Where is that -- in the world.

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‫So let's go ahead and grab off the -- owner and look for the transform.

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‫Property get actor transform.

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‫That would be the one.

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‫We'll pipe that in to our inverse transform direction and we've got ourselves a new vector out of this.

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‫So the next step would be to get the rotation of this vector.

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‫So we'll look going to look for rotation.

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‫See what we can find.

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‫We've got find look rotation, make rotation from axes to cotangent.

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‫Now, let's have a look at rotation from X vector.

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‫If you read the documentation here it says it's going to set the your and pitch from this vector but

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‫it won't set the role because it can't get that information from a vector.

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‫That's fine.

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‫We don't care about the role in this case.

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‫All we care about is the user because we want to see how far we're turning to the right or left.

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‫So rotation from X vector, that's the one that we want is going to return us a rotator.

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‫And for us to get just the user from that rotator, we're going to right click on the pin and hit split

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‫struct pin, which goes ahead and splits that struct into the roll pitch.

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‫And your you could do that on a vector as well.

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‫By the way, I think you can right click and let's see, I think I'd have to break the link to do it.

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‫So I'm not going to show you.

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‫But basically we've now got a user here and that's what we want to set.

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‫So again, many challenge set up the user to be the angle and test it out.

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‫So again, mini challenge set up the year to be an annual variable that goes into the blend space and

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‫test it out, try it out in the game and see if you're able to run around successfully.

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‫Okay.

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‫Welcome back.

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‫So we're going to drag in again angle, variable set angle, going to set the angle from the yaw and

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‫we're going to get the execution pin from the end of speed.

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‫I'm going to compile and save that and we're going to go over to the sandbox and hit play.

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‫And now let's try moving around.

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‫A controller would be ideal so you can test out the different gradients and the nuances.

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‫And sure enough, you can see if I start moving around now, I'm able to move backwards, I'm able to

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‫move forward, sprinting and sideways and 45 degrees.

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‫All of that works based on the maths that we've calculated to calculate our angle.

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‫Great stuff.

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‫So we've learned a lot about transforms and vectors and how you can transform vectors, both inverse

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‫and forward transforming.

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‫And in the next lecture, we're going to look at fixing this foot sliding that we are seeing here.

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‫I'll see you there.