Hello world. Your first program

Topics
Hello World?
Creating a Unity Project
The Unity Project Folder
MonoDevelop: Unity's Code Editor
Attaching Scripts to GameObjects
Start() and Update()
GameObject Prefabs and Instantiation
The HelloWorld Project

Hello World?
Hello World is often the first program written by anyone learning a new programming language.
Outputs "Hello World!" to the Console

Hello World?
The code of HelloWorld.cs is very simple:

Creating a Unity Project
From the menu bar, choose File > New Project…
Choose the location for your project folder
Mac OS X
Click the Set… button
Navigate to the right location
Type the project name into the Save As field
Click the Save button
Windows
Click the Browse… button
Navigate to the right location
Click the New Folder button and give the new folder the name of your project.
Click the Select Folder button

Creating a Unity Project
Set up defaults for 3D
Click the Create Project or Create button
Appendix A contains detailed instructions

Creating a Unity Project
The Project pane shows the contents of the Assets folder inside your Unity project folder
Right-click in the Project pane and choose Reveal in Finder (or Show in Explorer) from the pop-up menu

MonoDevelop: Unity's Code Editor
Unity uses MonoDevelop for code editing
MonoDevelop is a separate program developed by a different team
To open MonoDevelop, double-click any C# script in your Project pane
This will launch MonoDevelop
Though the launch process takes some time
You must save a document in MonoDevelop for it to recompile and update in Unity
On Windows, Microsoft Visual Studio may be used
Instructions for this can be found online

MonoDevelop: Unity's Code Editor
The MonoDevelop Window
Code Pane
Classes
Pane
Document
Outline
Pane

Attaching Scripts to GameObjects
To work in Unity, a C# script must be attached to a GameObject

Attaching Scripts to GameObjects
This makes the script a component of the GameObject

Start() and Update()
You make use of Start() and Update() in the HelloWorld project
void Start() {…}
Called once
Called immediately before the first Update() is called
void Update() {…}
Called every frame
This can happen over 200 times per second!
void Awake() {…} (not used in HelloWorld, but important)
Called once
Called at the moment the GameObject is created
Guaranteed to be called before Start()

GameObject Prefabs and Instantiation
A prefab is a mold from which GameObject instances can be made
Created by dragging a GameObject from the Hierarchy pane into the Project pane
Can be assigned to a script variable in the Inspector pane
public GameObject gameObjectPrefab;
Then, an instance of the prefab can be created in code
Instantiate( gameObjectPrefab );
This is used in HelloWorld to create thousands of instances of a Cube GameObject prefab

The HelloWorld Project
Output "Hello World!" to the Console pane
Once using Start()
Many times using Update()
Create a Cube prefab that reacts to gravity & physics
Instantiate an instance of the Cube prefab
Once using Start()
Many times using Update()
This will create a cascade of thousands of Cube instances
Over other physically-modeled objects

The HelloWorld Project
The final HelloWorld scene