All language subtitles for 003 Start() & Update()_Downloadly.ir_en

In this video, we're going to talk about the difference between start and update and just create a

little piece of code that allows us to move our object up every frame that the game is playing.

OK, let's jump in and get started.

Let's make sure you're awake and ready for action.

I'm going to start you off with a challenge to get the party started.

In other words, create a new 3D project within unity at a ground plane, create your player.

So add in a cube or a circle or sphere.

Whatever you think would be cool for your player are going to be adding a cube and then to rename your

player.

So pause the video, take on that challenge and I'll see you back here when you're done.

OK, step one, open up the unity hub, I'm going to click on you to create a new project.

This will be with twenty twenty point one for me, three day project I'm going to name this obstacle

course.

Doesn't matter so much what you've named yours, but that's what I'm naming mine.

And for me, I'll add that to my repos.

Unity, 3D location.

So click on Create that will create our unity project.

So give that a moment or two that will bring us to our template project.

I'm going to right click in my hierarchy and add a 3D object and this will be a plane block.

There we go.

Not exactly sure how big I'll need this yet, so I'll leave it as it is for the moment.

The next thing I'm going to do is create myself a player.

So right.

Click 3D object.

I'll make a cube, see the cubes a little bit underneath the ground plane.

So just bring that up slightly, OK?

And to give it a little bit of personality, I'm going to squash it down.

So on to scale squash, squash and then just move it.

So it's touching the ground ish again.

There we go.

Right now I'm going to rename my cue by clicking on Cueball clicking over in the Inspector.

I will rename that to be what I say.

I was going to call it dodgy.

Dodgy the player not because he's untrustworthy, just because he's good at he's nimble.

There we go.

And that should be where you're up to from your challenge.

Yep.

There are all the steps in the challenge.

Now, the purpose of this video is to show you the difference between start and update.

So to do that, we need to get some code.

We need to create ourselves a script.

So little micro challenge for you.

Go ahead and create a new script called Movea.

OK, so if you're not exactly sure, we'll do that together, right, click down in our project assets

folder up to create and see sharp script before we click anywhere else, I'm going to rename this Movea.

Or I guess if you're in North America mover, I should have pronounced it mover.

This is the script that's going to move our player.

You guessed it.

Now we've got three different ways we can attach our script to our player, which is an important thing

to do because we want to be moving the player itself and we need this script attached to it to do so.

So method number one is I could click on my player dog and not just so it's very clear I'm going to

rename this player and then in parentheses, dodgy.

Just so anyone who joins this project midway through, they're not completely confused about what on

earth a dog is.

It's a player whose name is Dog.

There we go.

So, well, we clicked on that.

I can drag Movea over into my Inspecteur that will add it there, or I can drag on top of the object

in my hierarchy, or I can click on add component and type in mover and click to add that way.

So I'll do that final method.

But just showing a few different ways that you can add a script as a component onto a game object.

Now we want to open up movies or double click on that should open up visual studio code.

You can see well I've got this open here.

I'm going to minimize the left hand side in a moment.

Let me just do a little bit of rearranging.

You can see that it will show us the script in our file.

Explorer, you can see.

Move it.

You see.

So if we have a whole bunch of scripts, you'll see them lined up in there.

Now, I'm just going to click to close that box.

I don't need to see that extra piece of information.

Now, there's a lot going on in this script, but we're just going to focus on a couple of things for

now and as we go, will expand and we'll get to all of these various things.

Don't worry about that.

But we're focusing on the fact that we have stopped and we have update.

Now, what unity is doing is saying anything that is within start, anything that we write in here,

any statements I will make, those statements happen.

I'll do those statements when this script first comes to life and I'll do them just once.

Update is something that it says I will do every single frame that this script is alive and within the

game.

What I mean by frame, will you?

I'm sure you've played a game and you've seen that it's 30 or 60 fps.

In other words, frames per second a frame is something that is calculating all of the things that need

to go on in your game and make those happen.

So it might say, OK, we need to move this character a little bit.

There might be another character over a little bit.

There might be some logic on some AI.

And all of those things are happening many, many, many times per second, because if they only happen

once per second, you're going to be like boing, boing, boing like that, be very jumpy and jerky.

So that's why things are happening a lot.

Every single frame sometimes is called a tick because it's happening on a regular basis.

But every single frame of our game, things happen in every single frame of our game.

Whatever we say to do in the update will be done.

Now, let's make this a little bit concrete, so let's have a look at our player dog as mine is cold.

And you can see that while I've clicked on w my move here, I can move it around.

What's happening when I move it around.

Well over now Inspector, you can see the transform values are moving.

So if I was to rotate my screen a little bit here, so we've got the read which relates to X to the

right and the Y is up in the Z is going into the screen.

You can see as I move to the right, the X value is increasing.

If I move to the left, the X value is decreasing.

And I can also come over here into the inspector and I could type in, say, zero, for example, that

will make this go exactly to zero.

Or I could mouse over the X or the Y or Z and I can click my mouse and slide along like this.

So you can see this is literally saying set the position in the world, two point forty four.

Now we're saying set it to, for example, minus two and we can do the same on the Y axis.

So set it to two and on the Z axis, set it to one, for example.

OK, now if you wanted to get right back to the centre again, we can put zero zero zero.

I'm just having to move between those now.

It's underground again so I can lift it back out of the ground.

OK, now I'm hammering this point home that as we move our object, these values are moving because

we're about to change that encode in our script.

So if we're back into our movie script, if we add into our START method something that allows us to

change the transform value, and the way we do this is to start by typing transform with a small t dot.

Translate with a large tea or capital tea and then open parentheses.

Let me just take a moment just to let you know what's going on here.

So transform means we are accessing the transform of this game object.

Why do I say this game object?

Well, we have put Movea dot seats onto our player, so when it's looking for transform, it's saying,

OK, the transform of the game object that I'm currently on.

So that's this component over here, this transform, it's the transform on our game object.

And we have in here a dot.

Now that's the dot operator which allows us to access something that is contained within transform or

is underneath transform or is some set of logic that we get by accessing transform.

And in this case, unity has a built in method which is translate, which basically means move.

OK, translate that's already created for us.

We get it for free.

It's one of the joys of using an engine some hard working engineer in Silicon Valley has created.

Translate for us to use.

Excellent.

And what are the rules of translate?

Well, what translate needs is for us to say where do you want me to go on the X and the Y and Z?

And you need to type that by saying X, Y, Z, except it won't know what X, Y and Z are.

They just representations it needs to see a number.

So what will go in here and change instead of X will say one instead of Y will say zero instead of Z

will say zero.

And then at the end of our statement we need to add a semicolon.

So I'm going to put my values back here to zero zero zero just for argument's sake, so we can see what

happens.

What we're saying is add to that.

We're not saying take it to one zero zero.

We're saying add one, add zero, add zero.

OK, so I'm going to click on Save.

OK, back into Unity.

Now, what I'm going to do is to make this easier to see is grab my green in my game window and move

that just next to the scene window.

So I have the two side by side that will allow me to stay looking in the same view and also see what

the camera is saying.

So when I click on play, notice what happens to the cube.

It goes jump to the right and how much of that jump to the right leg jumped one to the right?

So if I click on play, you'll see it returns back to zero, back to where things started out.

So that was us putting this simple, hey, move the cube or move the game object into stock.

What would happen if we put it into update?

Well, let's check that out.

If I highlight, highlight, highlight my transformed work translate and then cut on my keyboard.

So control X or command X and then paste control V, Command V to put this into update.

Now what we're saying is do this particular thing every single frame.

So if my computer is currently running at 60 frames per second, we'll move this one on the x axis 60

times per second.

So I'm going to hit save jump back over here.

I'm just going to reorient my camera a little bit because I have a feeling this is going to go flying

really fast.

And when I click on play.

Brewing goes off into the distance because it's moving every single frame, a one on the positive x

axis.

And one last thing before we move on.

I'm just going to make this a smaller increment so we can see it more easily.

So, for example, zero point zero one, if I save that, jump back over into unity, click on play.

You can see that we have an error.

Excellent.

I'm glad it gave me that error there.

If we if you see an error.

So if any time it says, oh, compiler error, this won't work, then what you need to do is jump into

the console and have a look to see what it is saying.

OK, saying that we have an argument one cannot convert double to float.

Excellent.

So this is what I was hoping would happen, is because not all numbers are created equal, there's different

types of representation of numbers.

What Unity is expecting in this instance is a floating point value or a float.

And to represent that, we need to put an F. after our numbers.

So for zero point zero, where they need to put an F. to say this is a float and it's not going to get

confused in theory, we should be putting them after the zero and after the zero as well.

So it's very clear what's going on.

But because there's no dot in there, there's no decimal place.

Unity is like I call, I've got it.

I know what you're talking about here, Rick.

It's just a straight up zero.

But when we've got our decimal place, it's a bit confusing and hit save back over into unity.

Watch to see if my issue goes away.

Yes, it does.

That error has gone away.

Click on play.

And now you can see we're moving at a more reasonable pace, so the reason I wanted to take you through

this was to show the difference between START, which is happening once, just when that script starts

or in our case, when we click on play for the game versus update, which is happening every frame.

And also to show you that this is the foundation for movement for our player, that we need to be having

something within update that says every single frame, I might wish to move my player and move it in

a particular spot.

Just so we've anchored that mechanism of movement is going to be taking place within update.

OK, good stuff.

Hope this all made sense.

If there's any questions at all, please throw your questions in the Q&A or the discussions and I'll

see you in the next lecture.