Scripting 101

Transform

Avertissement

Writing transform.position = P; is ok. But it is not allowed to set only one parameter: transform.position.x = 4

Coordinates

World

Vector3 P = transform.position;	Get position
float x = transform.position.x;	Get X-coordinate
transform.position = P;	Set position
transform.rotation = Quaternion.Euler(0f, 90f, 0f);	Rotation relative to the world axis

Local

Vector3 P = transform.localPosition;

transform.localrotation =

Moving

World

transform.Translate(dirVector3)	Translate by a given vector
transform.Translate(x, y, z)	Translate by x, y, z values
transform.Rotate(rotAngle3);	Rotate using a Vector3 angle
transform.Rotate(rx, ry, rz);	Rotate using individual angles on each axis

Local

transform.Translate(dirVector3, Space.Self)

transform.Rotate(rotAngle3, Space.Self);

Built-In Properties

There are predefined properties and methods that are automatically available in a MonoBehaviour script. Since they are not explicitly defined in the code, this can lead to some confusion.

gameObject	GameObject	The current GameObject this script is attached to
transform	Transform	The transform of the current gameObject
tag	string	The tag of the GameObject
name	string	The name of the GameObject
Instantiate(Class,pos,rot);	given Class	Create new gameObject in the scene

Lifecycle Methods

MonoBehavior functions automatically called by Unity

Start()	Used to initialize objects, variables, or references before the first frame update.
Update()	Every frame, handles non-physics updates: user input, animations and logic
FixedUpdate()	At fixed intervals (0.02s), used for physics-related logic and Rigidbody interactions
void OnTriggerEnter(Collider other)	Detect an object entering the collider set in trigger mode
void OnTriggerExit(Collider other)
void OnMouseOver()	Mouse pointer passes over the object
void OnMouseDown()	Mouse click on the object

Useful helper class

Some utility classes, imported by using UnityEngine, may be handy:

Debug.Log(..)	Debug	Display logs, warnings, and errors
Mathf.Abs(..)	Mathf	Mathematical functions: sin, cos, clamp, lerp, etc.
Random.Range(0, 3)	Random (int)	Integer random value among 0, 1, 2
Random.Range(0f, 3f)	Random (float)	Float random value like 0.4, 2.5…
Time.time	Time	Time since the start of the scene
Time.deltaTime		Time passed since the last frame
Input.GetKey(..)	Input	Reading keyboard
Input.mousePosition		Reading mouse
Input.GetAxis(« Horizontal »)		Reading joystick
SceneManager.LoadScene(..)	SceneManagement	Load or add a scene
PlayerPrefs.Set/Get	PlayerPrefs	Persistent data storage
Physics.Raycast(ray, ..)	Physics	Raycasting technique
Selection.activeGameObject	Selection	current selected gameObject in the scene view

Hierarchy

GameObject

All parent/child relationship are stored in the transform parameter of a gameobject:

GameObject obj = GameObject.Find(“Name”);	find an object by name
GameObject parent = obj.transform.parent.gameObject;	select its parent gameObject
foreach (Transform T in obj.transform) { }	parse its child gameObject
newobj.transform.SetParent(parentTransform)	set parent of a new object

Component

g.GetComponent<Rigidbody>()

Find a specific component of a GameObject

Misc

Raycasting

RaycastHit hit;
if (Physics.Raycast(position, vecDir, out hit, maxDist)) // throw a ray
{
        GameObject touchedObject = hit.collider.gameObject;
        Debug.Log("Hit: " + touchedObject.name);
}

Add a function in the Editor

using UnityEngine;
using UnityEditor;

public class NameOfMyClass
{
        [MenuItem("Tools/Generate 32 Materials")]   // new entry in the Tools menu
        public static void Go()  {...}
}

Coroutine

A coroutine if a function running asynchronously - use only for small process.

public class test : MonoBehaviour
{

        void Start()
        {
                StartCoroutine(MyCoroutine());  // Start the coroutine when the scene starts
        }

        IEnumerator MyCoroutine()
        {
                Debug.Log("Start");

                yield return new WaitForSeconds(3f); // Wait for 3 seconds

                Debug.Log("3 seconds later...");
        }

Lerp

Lerp stands for: Linear interpolation - Useful for animation:

// rotate smoothly
Quaternion targetRotation = Quaternion.Euler(0f, 180f, 0f);
transform.rotation = Quaternion.Lerp(transform.rotation, targetRotation, Time.deltaTime);