Baixe Unity - Scripting Tutorial e outras Notas de estudo em PDF para Desenvolvimento de Jogos Digitais, somente na Docsity! Introduction to scripting with Unity Scripting is an essential part of Unity as it defines the behaviour of your game. This tutorial will introduce the fundamentals of scripting using Javascript. No prior knowledge of Javascript or Unity is required. Time to complete: 2 hours. Author: Graham McAllister Contents 1. Aims of this tutorial 2. Prerequisites 3. Naming conventions 4. Player Input 5. Connecting variables 6. Accessing components 7. Instantiate 8. Debugging 9. Common Script Types 1. Aims of this tutorial Scripting is how the user defines a game’s behaviour (or rules) in Unity. The recommended programming language for Unity is Javascript, however C# or Boo can also be used. This tutorial will cover the fundamentals of scripting in Unity and also introduce key elements of the Application Programming Interface (API). You can think of the API as code that has already been written for you which lets you concentrate on your game design and also speeds up development time. A good understanding of these basic principles is essential in order to harness the full power of Unity. 2. Prerequisites This tutorial focuses on the scripting element of Unity, it is assumed you are already familiar with Unity’s interface (if not you should read the Unity GUI tutorial). In order to make scripting easier to understand, it is preferable to have a code editor that has syntax highlighting support for Javascript. This means that reserved words (syntax used by Javascript itself) are coloured differently than user defined words. One such editor is SubEthaEdit. NB: any text that requires the user to take an action begins with a ‘-’. 3. Naming Conventions Before we begin, it is worth mentioning some conventions in Unity. Variables - begin with a lowercase letter. Variables are used to store information about any aspects of a game’s state. Functions - begin with an uppercase letter. Functions are blocks of code which are written once and can then be reused as often as needed. Classes - begin with an uppercase letter. These can be thought of as collections of functions. Tip: When reading example code or the Unity API, pay close attention to the first letter of words. This will help you better understand the relationship between objects. 4. Player Input For our first program we’re going to allow the user to move around in a simple game world. Setting the scene - Start Unity. Firstly, let’s create a surface for the user to walk on. The surface we’re going to use is a flattened cube shape. - Create a cube and scale its x,y,z dimensions to 5, 0.1, 5 respectively, it should now resemble a large flat plane. Rename this object ‘Plane’ in the Hierarchy View. - Create a 2nd cube and place it at the centre of this plane. If you can’t see the objects in your Game View, alter the main camera so they’re visible. Rename the object to Cube1. - You should also create a point light and place it above the cubes so that they’re more easily visible. - Save the scene by selecting File->Save As and give the game a name. Our first script We’re now ready to start game programming. We’re going to allow the player to move around the game world by controlling the position of the main camera. To do this we’re going to write a script which will read input from the keyboard, then we attach (associate) the script with the main camera (more on that in the next section). - Begin by creating an empty script. Select Assets->Create->Javascript and rename this script to Move1 in the Project Panel. - Double-click on the Move1 script and it will open with the Update() function already inserted (this is default behaviour), we’re going to insert our code inside this function. Any code you insert inside the Update() function will be executed every frame. 2 - Attach the script to the spotlight and notice when the component gets added, the “target” variable is exposed. - With the spotlight still selected, drag the Main Camera from the Hierarchy View onto the “target” variable in the Inspector View. This assigns the target variable, i.e. the spotlight will now follow the Main Camera. If we wanted the spotlight to follow a different game object we could just drag in a different object (as long as it was of type Transform of course). - Play the game. If you watch the Scene View you should see the spotlight following the Main Camera around. You may want to change the position of the spotlight to improve the effect. 6. Accessing Components As a game object can have multiple scripts (or other components) attached, it is often necessary to access other component’s functions or variables. Unity allows this via the GetComponent() function. We’re now going to add another script to our spotlight which will make it look at Cube1 whenever the jump button (spacebar by default) is pressed. Let’s think about this first, what do we want to do: 1. Detect when the jump button has been pressed. 2. When jump has been pressed make the spotlight look at Cube1. How do we do this? Well, the Follow script contains a variable “target” whose value determines which game object the spotlight should look at. We need to set a new value for this parameter. We could hardcode the value for the cube (see the section ‘Doing it with code’ later), however we know that exposing the variable and assigning this via the GUI is a better way of doing this. - Create a new Javascript and name it Switch. Add the following code to Switch.js: var switchToTarget : Transform; function Update () {   if (Input.GetButtonDown("Jump"))     GetComponent(Follow).target = switchToTarget; } Notice in particular how Follow is the parameter to GetComponent(), this returns a reference to the Follow script which we can then use to access its “target” variable. - Add the Switch script to the spotlight and assign Cube1 to the switchToTarget parameter in the Inspector View. - Run the game. Move around and verify that the spotlight follows you as usual, then hit the spacebar and the spotlight should focus on the Cube1. Doing it with code Earlier in the tutorial we mentioned that it would be possible to assign the variables via code (as opposed to the Unity GUI), let’s take a look at how you would do that. 5 Remember this is only for comparison, assigning variables via the GUI is the recommended approach. The problem we were interested in earlier was how do we tell the spotlight to look at Cube1 when the jump button was pressed. Our solution was to expose a variable in the Switch script which we could then assign by dropping Cube1 onto it from the Unity GUI. There are two main ways to do this in code: 1. Use the name of the game object. 2. Use the tag of the game object. 1. Game object name A game object’s name can be seen in the Hierarchy View. To use this name with code we use it as a parameter in the GameObject.Find() function. So if we want the jump button to switch the spotlight from Main Camera to Cube1, the code is as follows: function Update () {   if (Input.GetButtonDown("Jump"))   {     var newTarget = GameObject.Find("Cube").transform;     GetComponent(Follow).target = newTarget; } } Notice how no variable is exposed as we name it directly in code. Check the API for more options using Find(). 2. Game object tag A game object’s tag is a string which can be used to identify a component. To see the built-in tags click on the Tag button in the Inspector View, notice you can also create your own. The function for finding a component with a specific tag is GameObject.FindWithTag () and takes a string as a parameter. Our complete code to do this is: function Update () {   if (Input.GetButtonDown("Jump"))   {     var newTarget = GameObject.FindWithTag("Cube").transform;     GetComponent(Follow).target = newTarget; } } 6 7. Instantiate It is often desirable to create objects during run-time (as the game is being played). To do this, we use the Instantiate function. Let’s show how this works by instantiating (creating) a new game object every time the user presses the fire button (either the left mouse button or left ctrl on the keyboard by default). So what do we want to do? We want the user to move around as usual, and when they hit the fire button, instantiate a new object. A few things to think about: 1. Which object do we instantiate? 2. Where do we instantiate it? Regarding which object to instantiate, the best way of solving this is to expose a variable. This means we can state which object to instantiate by using drag and drop to assign a game object to this variable. As for where to instantiate it, for now we’ll just create the new game object wherever the user (Main Camera) is currently located whenever the fire button is pressed. The Instantiate function takes three parameters; (1) the object we want to create, (2) the 3D position of the object and (3) the rotation of the object. The complete code to do this is as follows (Create.js): var newObject : Transform; function Update () {   if (Input.GetButtonDown("Fire1")) {   Instantiate(newObject, transform.position, transform.rotation);   } } Don’t forget that transform.position and transform.rotation are the position and rotation of the transform that the script is attached to, in our case this will be the Main Camera. However, when an object is instantiated, it is usual for that object to be a prefab. We’ll now turn the Cube1 game object into a prefab. - Firstly, let’s create an empty prefab. Select Assets->Create->Prefab. Rename this prefab to Cube. - Drag the Cube1 game object from the Hierarchy View onto the Cube prefab in the Project view. Notice the prefab icon changes. Now we can create our Javascript code. - Create a new Javascript and name it Create. Insert the above code. - Attach this script to the Main Camera and assign the Cube prefab to the newObject variable of Main Camera. - Play the game and move around as usual. Each time the fire button is clicked (LMB or left ctrl) and you should notice a new cube appearing. 7