Unity ScriptingWith C# or “JavaScript”

Telerik School Academyhttp://academy.telerik.com

Unity 2D Game Development

Table of Contents1. Creating and Using Scripts2. Variables Sent To Inspector3. Controlling Objects and

Components4. Input From Mouse, Touch,

Keyboard5. Game Loop and Events6. Time Management7. Creating and Destroying Game

Objects8. Coroutines9. Saving and Loading10.Good Practices

2

Creating and Using ScriptsAdd Script Components To

Objects

Creating and Using Scripts

Scripts are just normal components added to objects

They are not built-in, you "code" them and then compile them

They give you more control Can be written in C# (Mono) or

"JavaScript" (Unity style) Other .NET languages are

compatible (sort of)

4

Creating and Using Scripts

To add new script to an object select it and click "Add Component"

Start writing the name of the script – ex. "PlayerController"

Or simply write click on any directory on the "Project Browser", create it from there and drag it to an object

You should forget most OOP principles from now on – Unity is component-based and has its own standards

5

Default Script Parts Double-clicking a script will open it

in your IDE There are couple of things to

remember All components inherit from

MonoBehavior class All components are using the

UnityEngine namespace Do not declare anything in

namespaces (although Unity claims to support it)

Non-component classes (not attached to objects) do not need above requirements

6

Default Script Parts Start and Update functions are

included You may add FixedUpdate if using

Physics

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using UnityEngine;

public class MainPlayer : MonoBehaviour { // Use this for initialization void Start () { } // Update is called once per frame void Update () { }}

Default Script Parts Use Start method for initialization

Set needed variables Do not initialize with constructors Use the predefined methods -

GetComponent Use Update method for object

update on every frame – read input, change parameters

Use FixedUpdate method for Physics update to Rigidbodies – add forces, colliders

Use Debug.Log for debugging purposes

8

Platform Dependent Scripting

Sometimes you need to execute code on certain platforms:

More here: http://docs.unity3d.com/Manual/PlatformDependentCompilation.html 9

#if UNITY_EDITOR Debug.Log("Unity Editor");#elif UNITY_IPHONE Debug.Log("Unity iPhone");#elif UNITY_STANDALONE_WIN Debug.Log("Stand Alone Windows");#else Debug.Log("Any other platform");#endif

Variables Sent To Inspector What is supported by the

editor?

Variables and Inspector It is common to use some sort of

parameters to make the game work Movement speed Offsets Texts More

The easiest way is to set a public field

The editor will find it right away You will be able to change the

value run-time

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private string myName;

Variables and Inspector Which fields can be serialized:

Public or with [SerializeField] attribute

Non-static, non-constant, non-readonly

Which types can be serialized: Primitive data types Custom non abstract classes and

structs with [Serializable] attribute Children of UnityEngine.Object Array or List<T> of serializable

types Avoid serializing complex objects

12

Controlling Objects and Components

The true power of Unity

Accessing Components From code you can change all

components' parameters to make the game change each frame

Additionally you can call methods, which are not available through the editor

Most common case Declare private variable for the

component in the class Get the component in the Start

method Change it in the Update method 14

Accessing Components Example:

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using UnityEngine;

public class MainPlayer : MonoBehaviour { private RigidBody2D rigidbody;

void Start () { this.rigidbody = this.GetComponent<RigidBody2d>(); }

void Update () { this.rigidbody.mass = 10f; this.rigidbody.AddForce(Vector2.Up * 10f); }}

Accessing GameObjects You can access other GameObjects

Add public GameObject variable Drag'n'drop the object in the editor

to assign it

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using UnityEngine;

public class MainPlayer : MonoBehaviour { public GameObject enemy;

void Start () { this.transform.position = this.enemy.transform.

position – Vector3.forward * 10f; }}

Accessing GameObjects You can access other GameObjects'

components Add public variable of the

component Drag'n'drop the object

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using UnityEngine;

public class MainPlayer : MonoBehaviour { private Transform enemy;

void Start () { this.transform.position = this.enemy.

position – Vector3.forward * 10f; }}

Finding Game Objects You can find other objects by tag

or name

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using UnityEngine;

public class MainPlayer : MonoBehaviour { private GameObject enemy; private GameObject[] enemies;

void Start () { this.enemy = GameObject.Find("Boss"); // name this.enemy = GameObject.FindWithTag("Boss"); // tag this.enemies = GameObject. FindGameObjectsWithTag("Enemy"); // collection }}

Important Classes Most important classes

MonoBehaviorhttp://docs.unity3d.com/ScriptReference/MonoBehaviour.html

Transformhttp://docs.unity3d.com/ScriptReference/Transform.html

Rigidbody2Dhttp://docs.unity3d.com/ScriptReference/Rigidbody2D.html

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Device InputMouse, Keyboard,

Touchscreen

Input Input

All player input is accessed via the static Input class (do it in the Update)

You can read Buttons

Input Axes (Horizontal, Vertical)

Mouse movements

Accelerometer, Gyroscope

Multi-touch presses on touch screens

Edit -> Project Settings -> Input 21

Get Key You can use GetKey, GetKeyDown

and GetKeyUp All captured input is saved until

the next Update call This looks quite straightforward But avoid using it – you are device

dependent Not all devices have the same

buttons

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if(Input.GetKeyDown(Keycode.Space)){ //Jump Code}

Get Button Buttons are way more generic They are not device dependent For example "Fire1" button is for

left-mouse click, tap on touchscreen and CTRL key on keyboards

Use GetButton, GetButtonDown and GetButtonUp

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if(Input.GetKeyDown(Keycode.Space)){ //Jump Code}

Get Input Axes Input axes are mainly used for

movement Give you much smoother

experience "Horizontal" and "Vertical" Usually they return values

between -1 and 1 Depending on the direction Depending on the time the button

was pressed24

var hor = Input.GetAxis("Horizontal") * speed;this.transform.Translate(

new Vector3(hor, 0, 0) * Time.deltaTime);

Other Types of Input To get touchscreen information

Input.touches and Input.Touch structure

To get accelerometer information Input.acceleration

To get location information Input.location

To get mouse information Input.mousePosition

More here: http://docs.unity3d.com/ScriptReference/Input.html

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Game Loop and Events

How The Game Is Running

Game Programming Game programming is usually

rendering frame after frame Before each frame different

calculations are done Object Positions and Rotations Colliding Physics

Unity fires different events before and after rendering the next frame

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Regular Update Events Update

Called once per frame (not fixed time)

Executed before frames and animations

Perfect for inputs and getting different states of objects

FixedUpdate Called every fixed time seconds –

0.02 default Perfect for Physics Engine updates

and code LateUpdate

Called after all calculations Perfect for code that you want to

run after the frame is updated

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Physics Events OnCollisionEnter2D,

OnCollisionStay2D, OnCollistionExit2D Called on every collision Enter – when collision starts Stay – when collision occurs Exit – when collision ends

OnTriggerEnter2D, OnTriggerStay2D, OnTriggerExit2D Fired only on trigger collisions

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Other Events Start

Called before the first frame of Physics update on the object

Awake Called before the scene is loaded

and before the Start is called OnGUI

All GUI elements will respond to this event

OnMouseOver, OnMouseDown When a object has a mouse over or

clicked on 30

Game Loop Part 1

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Game Loop Part 2

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Time ManagementTime Is Money

Time Management Since the Update function is not

called on regular time intervals, you may get certain “lag” If the framerate drops Different CPU load

Consider the following code

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public float distancePerFrame; void Update() { transform.Translate(distancePerFrame, 0, 0);}

Time Management If the framerate drop, you may see

different “laggy” results in the gameplay

The object will move with irregular speed

Solution is to scale all time dependent vectors (for example movement) with the delta time

You can get it from Time.deltaTime field

Now the object’s speed will be constant

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public float distancePerFrame; void Update() { transform.Translate(distancePerFrame, 0, 0) * Time.deltaTime;}

Creating And Destroying

Game ObjectsUseful Techniques

Creating Game Objects It is very common to create

different objects run-time Usually you should use prefabs Instantiate method is used

Just drag’n’drop an object to the editor’s enemy field

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public GameObject enemy;

void Start() { for (int i = 0; i < 5; i++) { Instantiate(enemy); }}

Destroying Game Objects

There is also an Destroy method You can set time after which the

object is destroyed

Destroy can also destroy only component

The following will destroy the script

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void OnCollisionEnter2D(Collision2D otherObj) { if (otherObj.gameObject.tag == "Missile") { Destroy(gameObject, .5f); }}

Destroy(this);

CoroutinesSometimes very useful!

Coroutine All functions are finished to the

end before the next frame is updated

Because of this animations cannot be done directly with code

This function will not gradually fade the object – it will disappear directly

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void Fade() { for (float f = 1f; f >= 0; f -= 0.1f) { Color c = renderer.material.color; c.a = f; renderer.material.color = c; }}

Coroutine A coroutine will help you here Coroutine is executed over

sequence of frames instead of one Do declare coroutine The yielded value will pause until

the next frame of the game

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IEnumerator Fade() { for (float f = 1f; f >= 0; f -= 0.1f) { Color c = renderer.material.color; c.a = f; renderer.material.color = c; yield return null; }}

Coroutine Then all you need is to start the

routine

You can also set time interval for the coroutine

You can use coroutines to reduce the checks in the Update method

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void Update() { if (Input.GetKeyDown("f")) { StartCoroutine("Fade"); }}

yield return new WaitForSeconds(.1f);

Other Helpful Methods

Application!

Other Functions To invoke a method after certain

time

To load another scene

To quit the game

To pause the game set the Time.timeScale

And to resume set it to 1 44

Invoke("LoadLevel", 3f);

Time.timeScale = 0;

Application.LoadLevel("WinScene");

Application.Quit();

Saving And LoadingPersistence!

Saving And Loading The PlayerPrefs class have

methods to save and load values HasKey SetInt and GetInt SetFloat and GetFloat SetString and GetString

For saving and loading the whole game: http://goo.gl/3HZXZT

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PlayerPrefs.SetInt("High Score", highscore);var highscore = PlayerPrefs.GetInt("High Score");

Good PracticesHigh Quality Code is important!

http://goo.gl/xPcrAx

Summary Coding gives you good control of the

game mechanics

Public fields are exported to the inspector

Use GetComponent to set different components

Use time management in your Update functions

How to use the Input class

Use coroutines where needed48

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