In the last decades of the 20th century, research in information visualization and virtual reality made substantial progress, and results of these efforts have gradually been incorporated in the daily practice of professionals in science and engineering. Since the emergence of affordable, powerful personal computers, images and graphics have become essential elements in many computer applications for communication, education, and entertainment that are used on a daily basis by people at home as well. Many computer applications for professional or personal use contain 3-D models of buildings and cities that represent real or imaginary environments, often called virtual environments. The models may either serve as a setting for simulation and training, or may themselves represent the main purpose of the program and enable the user to explore a historical building or environment, or compare the different designs made by architects for a new community building. These 3-D models of buildings and larger environments have become indispensable elements in computer games, and in applications with educational, military, and many other purposes. Research in development of these models has concentrated on technical and cognitive issues such as depth perception or distance estimation, often driven by the intent to make the models look “photo realistic” and to make navigation as easy as possible.