How should users interact with the virtual world? How should they move about? How can they grab and place objects? How should they interact with representations of each other? How should they interact with files or the Internet? The following insight suggests many possible interfaces.
Universal Simulation Principle:
Any interaction mechanism from the real world can be simulated in VR.
For example, the user might open a door by turning a knob and pulling. As another example, the user operate a virtual aircraft by sitting in a mock-up cockpit (as was shown in Figure 1.16). One could even simulate putting on a VR headset, leading to an experience that is comparable to a dream within a dream!
In spite of the universal simulation principle, recall from Section 1.1 that the goal is not necessarily realism. It is often preferable to make the interaction better than reality. Therefore, this chapter introduces interaction mechanisms that may not have a counterpart in the physical world.
Section 10.1 introduces general motor learning and control concepts. The most important concept is remapping, in which a motion in the real world may be mapped into a substantially different motion in the virtual world. This enables many powerful interaction mechanisms. The task is to develop ones that are easy to learn, easy to use, effective for the task, and provide a comfortable user experience. Section 10.2 discusses how the user may move himself in the virtual world, while remaining fixed in the real world. Section 10.3 presents ways in which the user may interact with other objects in the virtual world. Section 10.4 discusses social interaction mechanisms, which allow users to interact directly with each other. Section 10.5 briefly considers some additional interaction mechanisms, such as editing text, designing 3D structures, and Web browsing.