Augmented Reality (AR) offers us a new way to interact with the physical (or real) world. It creates a modified version of our reality, enriched with digital (or virtual) information, on the screen of your desktop computer or mobile device. Merging and combining the virtual and the real can leverage a totally new range of user experience, going beyond what common apps are capable of. Can you imagine playing a first-person shooter in your own neighborhood, with monsters popping up at the corner of your street (as it is possible with ARQuake by Bruce Thomas at the University of South Australia, see left-hand side of the following screenshot)? Will it not be a thrilling moment to go to a natural history museum and see a dusty dinosaur skeleton coming virtually alive—flesh and bone—in front of your eyes? Or can you imagine reading a story to your kid and seeing some proud rooster appear and walk over the pages of a book (as it is possible with the AR version of the "House that Jack Built" written by Gavin Bishop, see the right-hand side of the following screenshot). In this book, we show you how to practically implement such experiences on the Android platform.

A decade ago, experienced researchers would have been among the few who were able to create these types of applications. They were generally limited to demonstration prototypes or in the production of an ad hoc project running for a limited period of time. Now, developing AR experiences has become a reality for a wide range of mobile software developers. Over the last few years, we have been spectators to great progresses in computational power, the miniaturization of sensors, as well as increasingly accessible and featured multimedia libraries. These advances allow developers to produce AR applications more easily than ever before. This already leads to an increasing number of AR applications flourishing on mobile app stores such as Google Play. While an enthusiastic programmer can easily stitch together some basic code snippets to create a facsimile of a basic AR application, they are generally poorly designed, with limited functionalities, and hardly reusable. To be able to create sophisticated AR applications, one has to understand what Augmented Reality truly is.

In this chapter, we will guide you toward a better understanding of AR. We will describe some of the major concepts of AR. We will then move on from these examples to the foundational software components for AR. Finally, we will introduce the development tools that we will use throughout this book, which will support our journey into creating productive and modular AR software architecture.

Ready to change your reality for Augmented Reality? Let's start.