1 What Are Augmented Reality and Virtual Reality?

Even a few years ago, relatively few people had experienced augmented reality or virtual reality because the required hardware was expensive and the software difficult to use. Now several million VR headsets are shipped each year from various manufacturers—Sony, Oculus, HTC, and others (Statista, n.d.). Many gamers have experienced VR versions of role-playing games (RPGs), construction games, driving games, sports games, or first-person shooters (FPSs) such as Valve's Half-Life: Alyx (figure 1.1).