Unity 2D

01. Basics

• Open project, select 2D
• Project Browser - all files in the project, create folders
• Hierarchy - all game objects and their combinations
  • double click to center on object
  • create empty object to use like folder
• Inspector - all properties of selected game object
  • Transform - change position, rotation and scale
  • Settings of obect (size of camera is 1/2 of height)
  • Components - scripts, rigid body...
• Camera - at least 1 camera (we can have more)
  • Scene - add and manipulate objects
  • Game - camera proportions and preview window
• Layers - ways to separate objects
• Publishing builds
  • Build settings - and Build

Game objects

• everything is game object
• default components - Name, Tag, Layer, Transform
  • use Tag for selection
  • sorting layer - will order objects based on their order
• static option - object will not be calculated
• optional components
  • sprite
  • camera
  • animation
  • physics (rigid body 2D)
  • script

Prefabs

• create custom object that can be dublicated
• make folder "Prefabs" and drag object inside (from Hierarchy)
  • if blue than it is part of prefab
  • break prefab instance - detatch from prefab
• ctrl + D clone objects

02. Mathematics

Vectors

var vector = Vector2.one; // (1, 1)
var right = Vector2.right; // (1. 0)
var left = -Vector2.right;
var up = Vector2.up; // down -> -up
var velosity = velocity + gravity; // sum of vectors
var velosity = 0.7 * velosity; // scalar
var length = velosity.magnitude; // length of vector
var lengthSqrt = velosity.sqrMagnitude; // faser calculation of square length
var distance = Vector2.Distance(first, second); // find distance between 2 vectors
var normalized = position.normalized; // make length 1
var dotProduct = Vector2.Dot(position, speed); // check position between 2 vectors
var angle = Vector2.Angle(position, direction); // find angle between

Mathf.Clamp(10, 1, 3); // arrange numbers between

03. Physics

Physics Components

• Rigidbody 2D - gravity and forces will apply
  • do not change transform component from scripts
  • use only forces to transform object
  • use is kinematic to make object not moveable
  • at least one collider must have rigid body
• Box Collider 2D
• Circle Collider 2D
• Polygon Collider 2D
• Edge Collider 2D
  • register collisions
  • both object need to have collider
  • one of the objects must have rigid body
  • can make invisible colliders
• Is Trigger
  • Physics is not working bur Unity registeres it
  • Event can be catched and used in code
  • OnTriggerEnter2D()
  • OnTriggerStay2D()
  • OnTriggerExit2D()
• Static Collider
  • If collider does not have Rigidbody - do not move!

Physics Materials

• Create material first - Assets -> Materials -> create
• Friction - coefficient
• Bounciness - from 0 - no bounce to 1 - full bounce

Joints

• Different types of joints
• Attach to object or point in space

04. Scripts

using UnityEngine;

// "this" is the game object that is manipulated
public class SpeedController: MonoBehaviour
{
    // if we know other game object, use this
    public GameObject gameObj; // shows in editor, can drag any game object
    public otherTransform gameObjTransform; // can get componet only from other object

    public float speed = 0.5f; // use public field for editor incpector
    private float movement; // does not show in editor
    private Rigidbody2D rb; // to use components

    private float offestX; // offset X between this and camera
    private float offestY; // offset Y between this and camera
    
    void Start() {
        // do something before start
        this.rb = this.GetComponent<Rigidbody2D>(); // gets the instantiated component, slow operation - do in start

        // find offset between this and camera
        this.offsetX = this.transform.position.x - Camera.main.transform.position.x;
        this.offsetY = this.transform.position.y - Camera.main.transform.position.y;
    }

    // do before every visualisation
    void Update() {
        // read input and direct changes to animation, time is not fixed
        var position = this.transform.position; // need to use local var
        position.x += speed; // change it
        this.transform.position = position; // and then set the transform

        // move camera with this
        var goPosition = Camera.main.transform.position;
        goPosition.x = this.transform.position.x + this.offsetX;
        goPosition.y = this.transform.position.y + this.offsetY;
        Camera.main.transform.position = goPosition;

        // If we do not know game object at first time, find it here
        var go = GameObject.FindWithTag("myTag"); // gets first
        var gos = GameObject.FindGameObjectsWithTags("myTag"); // gets all
    }

    void FixedUpdate() {
        // apply physics here, makes calculations between 0.02 sec fixed
        this.rb.AddForce(new Vector2(10, 15)); // change component

        Debug.Log(this.transform.position.x - this.gameObj.transform.position.x); // use other game object
    }
}

• can use different types - bool, int, lists, enumerations
• can use custom class with [Serializable] attribute (shows public fields)
• for private fields use [SerializeField] attribute

Code executions for different platforms

#if UNITY_EDITOR
    Debug.Log("Unity editor")
#elif UNITY_IPHONE
    Debug.Log("Unity iPhone")
#elif UNITY_ANDROID
    Debug.Log("Unity android")
#elif UNITY_STANDALONE_WIN
    Debug.Log("Other platform")
#endif

05. Read Input

• Buttons
• Input Axes (Horisintal, Vertical)
• Mouse movements
• Axelerometer, Gyroscope
• Keyboard
• use InputManager to setup inputs in editor

// this is not good, because not cross-platform
if(Input.GetKey(KeyCode.Space))
{
    Debug.Log("Space");
}

// use generic buttons - set them in editor
if(Input.GetButton("Fire1"))
{
    this.transform.position.Translate(new Vector2(0, 1));
}

06. Events

• Start
• Awake
• OnGUI
• OnMouseOver, OnMouseDown

07. Time Management

• If we multiply by Time.DeltaTime we can scale vectors
• this makes movement smooth

08. Destroy and Create game objects

• use prefabs (created in project)
• create empty game object with script used to instantiate new objects

public GameObject enemy; // add game object in editor

public void Start()
{
    var position = enemy.transform.position;
    position.x = 2.5f;
    position.y = 4.8f;
    enemy.transform.position = position;

    var go = Instantiate(enemy);
}

public void OnTriggerEnter2D(Collider2D other)
{
    Destroy(Other.gameObject, 1); // destroy after time seconds
}

public void Update()
{
}

09. Coroutines

• add for cycle that each iteration is done every frame

private spriteRend;

public void Start()
{
    this.spriteRend = this.GetComponent<SpriteRenderer>();
    StartCoroutine("Fade");
}

private IEnumerator Fade() 
{
    for(float i = 1; i > 0; i -= 0.01f )
    {
        var color = this.spriteRend.color;
        color.a -= i;
        this.spriteRend.color = color;
s
        yield return null; // executed every frame
        yield return new WaitForSeconds(0.1f); // executed after fixed time
    }
}

10. Other finctions

• Invoke("LoadLevel", 3f); - start method after certain time
• Application.LoadLevel("WinScene"); - load another scene
• Application.Quit(); - quit the Game
• Time.timeScale = 0 - this will pause the game, set it to 1 to resume

Player Preferences - use to save and load

PlayerPrefs.HasKey("name");
PlayerPrefs.RemoveKey("name");

PlayerPrefs.SetInt("HiScore", this.score);
PlayerPrefs.GetInt("HiScore");

PlayerPrefs.SetFloat("name", value);
PlayerPrefs.GetFloat("name");

11. Better save and load - Read article here

12. Best practices in Unity - Read this article

13. Unity documentation - Locaded here