In many applications, it is advantageous for users to see the live, real world with some additional graphics superimposed to enhance its appearance; see Figure 1.20. This has been referred to as augmented reality or mixed reality (both of which we consider to be part of VR in this book). By placing text, icons, and other graphics into the real world, the user could leverage the power of the Internet to help with many operations such as navigation, social interaction, and mechanical maintenance. Many applications to date are targeted at helping businesses to conduct operations more efficiently. Imagine a factory environment in which workers see identifying labels above parts that need to assembled, or they can look directly inside of a machine to determine potential replacement parts.
These applications rely heavily on advanced computer vision techniques, which must identify objects, reconstruct shapes, and identify lighting sources in the real world before determining how to draw virtual objects that appear to be naturally embedded. Achieving a high degree of reliability becomes a challenge because vision algorithms make frequent errors in unforeseen environments. The real-world lighting conditions must be estimated to determine how to draw the virtual objects and any shadows they might cast onto real parts of the environment and other virtual objects. Furthermore, the real and virtual objects may need to be perfectly aligned in some use cases, which places strong burdens on both tracking and computer vision systems.
Several possibilities exist for visual displays. A fixed screen should show images that are enhanced through 3D glasses. A digital projector could augment the environment by shining light onto objects, giving them new colors and textures, or by placing text into the real world. A handheld screen, which is part of a smartphone or tablet could be used as a window into the augmented or mixed world. This is the basis of the popular Nintendo Pokemon Go game; Figure 1.21. The cases more relevant for this book involve mounting the display on the head. In this case, two main approaches exist. In a see-through display,, the users see most of the real world by simply looking through a transparent material, while the virtual objects appear on the display to disrupt part of the view. Recent prototype headsets with advanced see-through display technology include Google Glass, Microsoft Hololens, and Magic Leap. Achieving high resolution, wide field of view, and the ability to block out incoming light remain significant challenges for affordable consumer-grade devices; however, it may become well-solved within a few years. An alternative is a pass-through display, which sends images from an outward-facing camera to a standard screen inside of the headset. Pass-through displays overcome current see-through display problems, but instead suffer from latency, optical distortion, color distortion, and limited dynamic range.
Steven M LaValle 2020-01-06