Unity

• A game engine that combines visual scene editing with scripting.
• Proprietary application, license by Unity Technology. Free version available for individuals or small companies.
• Provides deliverables for a great variety of platforms, including online and mobile.
• Currently dominates the game development market, and is extending into other production areas.
• Provides a variety of useful tools and a comprehensive library.

Features of Unity

• Scripting can be done in C# or JavaScript.
• Choice between 2D and 3D games.
• Integrated physics engine.
• Integrated collision detection. A variety of (editable) colliders that can be attached to game objects and trigger functions.
• Other useful tools: skyboxes, particle systems, light sources.
• Provides a set of game templates that we can start from.

Project

• Applications start out as projects.
• A project is composed of one or more scenes.
• A playable executable results from one or more scenes.
• A scene contains a display area, with a camera defining its size and properties, and several game objects.
• The Hierarchy contains a list of all the game objects in a scene together with their dependencies.
• The Inspector displays all the attributes and components of the selected game object.
• Resources are organized in Assets.

Special Classes

• All the objects created in a scene belong to classes derived from GameObject.
• All the scripts attached to game objects defining their functionality are derived from MonoBehavior.
• The object that a script is attached to is identified by gameObject.
• The script component itself is referenced by "this".
• The script has access to components of the game object through calls to GetComponent<name>()

Callback Functions

• The class MonoBehavior defines several callback functions that can be overloaded by derived classes to attach behavior to specific events.
• Start - called once when the program is loaded.
• Update - called once every frame of the game. Allows interaction with the Input class.
• OnGUI - allows interaction with key/mouse events through the Event class.
• OnMouseOver, OnMouseExit, etc. - more specific events. Some of them require a collider.
• OnTrigger - callback for collision detection.

More on Objects

• Finding a game object with a given name:
• Game Object objRef;
• objRef = GameObject.Find("objName");
• Some attributes/ components can be accessed directly
• rigidBody2D.AddForce(...);
• GetComponent<RigidBody2D>().AddForce(...);

Tutorials

• 2D animation and physics tutorial:
• https://unity3d.com/learn/tutorials/s/2d-game-creation
• http://brackeys.com/preview/2d-course/