All of the projects in this book will be built using the Unity 3D game engine. Unity is a powerful, cross-platform 3D environment with a user-friendly development editor. It consists of an amalgamation of various modules for managing and rendering 3D objects, lighting, physics, animations, audio, and more. It is also widely used for developing 2D games; however, the only 2D-specific features we will use in a project are the screen-space user interface (UI). Each of the Unity modules has a programmer interface, or API, with a rich set of classes and functions, so the entire system can be accessed through scripts written in the C# programming language.

Unity provides a range of subscription and licensing options. For more details, see https://store.unity.com/. The basic Personal version is free to download and use, and is great for AR development. In fact, the Personal version has all the same features of the paid versions! You need to go to a paid version only if your product revenue exceeds $100K or if you want to use Unity's suite of additional online services for professional developers.