An Introduction to and History of Virtual Reality

Introduction

One definition of virtual reality is a wide-field presentation of computer-generated, multi-sensory information that tracks a user in real time. This definition is used at the Electronic Visualization Laboratory in Chicago (EVL).

In other words, virtual reality means that the user is surrounded by a computer-generated image that changes depending on the movements--i.e. shifts in perspective--of the user.

Tracking

An important aspect of any immersive system is tracking. To create the illusion of a real surrounding, and not just a computer image, the image must change when the user's position (and thus perspective) inside the virtual world changes. To do this, the system has to keep track of where the user's eyes are and in what direction they are looking. This will allow the perspective shown in the images to change according to the user's movements, which gives the user the same impression of objects as in a real surrounding.

This is inherently difficult, and even more so in the fully immersive environment of the six-surface Cube system.

First steps in virtual reality

HMD--helmets

The first attempt at virtual reality used head-mounted displays (HMDs). In HMDs, projectors feed realtime images to small screens attached inside a kind of helmet that the user wears.

In the beginning, HMDs often showed mono pictures, and the user's head movements were tracked. In modern HMDs, stereo pictures are standard, since the technique has become cheaper. Typically, HMDs either have poor resolution or are too heavy.

Because only one person at a time can use an HMD, discussion of images is much more difficult.

BOOM--Binocular Omni-Orientation Monitor

To increase image quality, Fakespace invented the BOOM (Binocular Omni-Orientation Monitor). Very small monitors are mounted on a mechanical arm, and users look into the monitors like they would look into a pair of binoculars. Tracking occurs when the user moves the arm, which changes the perspective.

When a user releases the BOOM, another person can look at the same thing from the same perspective, which is an advantage over HMDs. Since real monitors are used, the resolution is good.

CAVE--CAVE Automatic Virtual Environment

The concept of a room with graphics projected from behind the walls was invented at EVL in 1992. The images on the walls are usually in stereo to give a depth cue. The main advantage over ordinary graphics systems is that the users are surrounded by the projected images, which means that the images are the users' main field of vision.

This is usually called a "CAVE", CAVE Automatic Virtual Environment. The first CAVE (as well as the concept) was created by the faculty, staff, and students at EVL.

Since then this back-projection method of virtual reality has gained a strong following. It has obvious benefits: it is easy for several people to be in the room simultaneously and therefore see images together; and it is easy to mix real and virtual objects in the same environment. Also, because users see for example their own hands and feet as part of the virtual world, they get a heightened sense of being inside that world.

Existing CAVEs

Various CAVE-like environments exist all over the world today. Most of these have up to four projection surfaces; images are then usually projected on three walls and the floor. Adding projection on the ceiling gives a fuller sense of being enclosed in the virtual world.

Projection on all six surfaces of a room allows users to turn around and look in all directions. Thus, their perception and experience are never limited, which is necessary for full immersion.

The PDC Cube is the first fully immersive CAVE.

Areas of use

An immersive visualization environment can be used for everything from science to art, and from industrial simulations to education. A few important areas are listed below, but there are numerous examples and fields that can benefit from a 3D visualization environment.

Scientific visualizations

In the scientific society, there is a trend towards 3D simulations. This has resulted in a rapidly growing need for 3D visualization of scientific data. Examples of projects at PDC in this area include EnVis, a tool for CFD (Computational Fluid Dynamics) visualization.

Visual simulations

There is also a growing need for visual simulations in industry. 3D simulations make it possible to test future products or to investigate otherwise unreachable environments.

Other areas of use

Education:
At KTH, the Stockholm Exhibition of 1930 has been modelled as an educational exercise in the architecture department. At NCSA, a CAVE is used for teaching mathematics by George Francis.

Architecture and city planning:
VR can be used in city planning, giving the opportunity to walk around in a city that has not yet been built.

Art:
There are many artistic applications for CAVE-like environments. In connection with the opening of PDC's Cube, an art workshop took place.