Beginning Unity 3D Scripting for Developers [Part 1]

Prerequisites

Basic Programming Knowledge

Unity 3D. Download it from here

Creating a New Project

When you start unity the first time you should see the Project Wizard dialog with two tabs, "Open Project" & "Create New Project". (If you don't see the Project Wizard dialog, go to File Menu -> New Project. In the "Create New Project" tab, type your desired folder name and click create. This is where the unity project will be saved. 

What you see now is a scene. Every object in your game has to be derived from the GameObject class. A GameObject itself doesn’t do anything, but is just a container for multiple Components (of type Component). Any number of components can be added to a GameObject. For example every game object comes with a Component called Transform, which defines the object's Position, Rotation and Scale.

One of the components that we will add today is called Script, which is just a class of type MonoBehavior (which as you might have guessed eventually has Component as its parent).

As we don't have a Main() method exposed, there is no real entry point we can code. Instead what we will do is create a new GameObject called "Main", and attach a script to it which will act as our "pseudo" entry point method. Once we add this game object to the scene, the code in the script will get executed.

Creating a new Empty GameObject

Keyboard Shortcut: Ctrl + Shift + N

Rename the object to Main (Select the newly created GameObject, right click -> Rename, or Press F2 and then type "Main")

Creating a new Script

Double click on the script (the file should be listed in the Assets window) and Mono Develop Editor should open up. Following is the default code created for you:

using UnityEngine;
using System.Collections;

public class Main : MonoBehaviour {

	// Use this for initialization
	void Start () {
	
	}
	
	// Update is called once per frame
	void Update () {
	
	}
}

The Start() and Update() Methods

Attaching the Script to GameObject

Our script will not run by itself. It has to be attached to a GameObject. Go back to Unity UI, drag the "Main" script file and drop it on to the Main game object.

Once you do this, when you select the Main game object, you should be able to see the Main (Script) component added to the GameObject, in the Inspector window on the right. 

Writing some code

void Start () {
	print ("Hello World");
}

Shortcut Ctrl+P

You should now be able to See "Hello World" printed in the Console Window. (Bottom Pane, select Console tab if not already active.

Exciting, isn't it? No? Well, let's add a Sphere.

Adding a Primitive Object

using UnityEngine;
using System.Collections;

public class Main : MonoBehaviour {
	GameObject sphere;
	// Use this for initialization
	void Start () {
		sphere = GameObject.CreatePrimitive (PrimitiveType.Sphere);
		sphere.renderer.material.color = Color.red;
	}
	
	// Update is called once per frame
	void Update () {
		
	}
}

You should see:

It looks more like circle as we haven’t yet added proper lighting. But you can click on the "scene" tab (which is kind of a debugger) and see it in a different "light".

Save your scene (File->Save Scene)

Next: Part 2