Virtual Environments

Background

Virtual environment is a concept that evolved from the term virtual reality, which was introduced by pioneers Myron Krueger and Jaron Lanier. The fundamental idea that originated virtual reality was in fact introduced by Ivan Sutherland, in a 1965 paper, “The Ultimate Display,” in which he had the vision of the computer as a “looking glass to a mathematical wonderland,” where the behavior of objects would not have to follow the physical properties found in nature. The experience with the ultimate display would be a complete sensory experience involving vision, hearing, touch, smell, and taste.

In classical virtual environments, the sensorial and motor systems of the user are connected to the computer through sensors and effectors. To generate the sensory stimuli, special-purpose simulation systems are used, already capable of real-time, threedimensional image and sound rendering and force feedback, but with limitations to the other senses. These effectors are used in conjunction with six degrees of freedom (x, y, z) and (yaw, pitch, roll), tracking sensors that together create a very appealing subjective sense of presence. This description constitutes what is usually called immersive virtual environment.

The immersive perspective proved to be inadequate for the state-of-the-art technology, and some problems still persist. This led to the emergence of augmented reality. In augmented reality systems, virtual and real environments are combined to form a unique environment shown to the user. Usually, it consists of a seethrough display where the information from the real world (usually obtained by video cameras) and from the digital world (coming from the computer) are overlaid. Augmented reality appeared as an opposite concept to virtual reality, because in augmented reality, the user is not inside an informational simulated [Page 504]reality, but instead augments the real world with superimposed data.

With the evolution of the Internet allowing increasing bandwidth, the virtual environment field suffered a redirection, and the focus became again the visual representation supported by very rich content availability. In recent years, there was another huge revolution in the field, with profound implications in geographic representation: the appearance of virtual three-dimensional representations of the earth's surface, accessible through the Internet (e.g., Digital Earth and Google Earth).

General Concepts

The fundamental characteristics of virtual environments are as follows:

• The generation of sensory stimuli in real time (e.g., with an almost immediate response to user actions)
• Three-dimensionality of inputs (for the user) generated

These characteristics influence the computational requirements in terms of hardware and software, namely, graphical performance and software techniques used to manage the interaction.

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