The following article comes from the book Virtual Reality Tomorrow: The Promise and Perils of VR in the 21st Century, which is being completed by VR eMAG publisher John C. Briggs. It is part of the book’s first chapter, “VR Today: The Promise of Virtual Reality.” Early drafts of this chapter and the introductory chapter of the book are available from VR eMAG, to order a hard copy, see details below.
What Is/Was VR? Definitions and Characteristics
There are a number of definitional debates that have been going on among VR practitioners and theorist for years. We have been debating: (1) what to call this technology arena, (2) an adequate definition for VR, (3) the characteristics necessary for something to be called VR, and (4) what technology is part of what technology (or mix of technologies) in the definitional hierarchy. Below I describe some of the various terms which have been used to describe what we now commonly call VR. Then I define VR and describe its characteristics.
Quite a number of VR people don’t like the term “Virtual Reality.” Some people prefer the term “virtual environments,” suggesting that it better describes experience in the virtual realm. They also suggest that their term gets around the issue of “virtual reality” being an oxymoron for them. How can something be virtually real? they ask. It can’t be both virtual and real at the same time. It’s either virtual or real. You will see “virtual environments” and “virtual worlds” used rather than VR in a number of articles by theorists, practitioners, and academicians. Don’t get confused, “virtual environments” and “virtual worlds” are generally the same thing as what we call “virtual reality.”
The military likes using the terms “synthetic environments” or “simulations” for its VR work. While these terms work for them, “synthetic environments” feels clumsy for most people and not very clear as to what it is. The synthetic world they create might not be an electronic world. It might even be a physical model made with synthetic materials. “Simulations” make people think of flight simulators. That’s fine. It’s a good way to explain what part of this technology is, but that is not all there is to VR.
Other people like the terms “3D interactive visualization” or “visual computing.” In many ways these terms come close to describing most VR experiences. The experience
should be 3D, interactive, visual, and generated by a computer. However, there is more to VR than just visualization. How about the other senses? Much of VR now includes not only vision, but also hearing. Future applications will use even more audio. While VR is primarily an audio-visual experience at present, in the future we may add smell, touch, and perhaps even taste to the experience. Additionally, what we now call VR should also be defined as an immersive experience of some sort. However, it’s awkward to say “a 3D, interactive, immersive, multi-sensory experience generated by a computer.” That’s a good, but complex, definition. It’s also a mouth full.
The terms “Virtual Reality” and “VR” have won out in common parlance at present. Jaron Lanier is credited with inventing the terms and, in many ways, popularizing them. The term Virtual Reality hooks us with the excitement of creating and experiencing different realities. It’s simple, easy to say, and rolls easily off the lips. The abbreviation VR also has a ring to it.
So, we use Virtual Reality and VR throughout this book to describe a technology which has been given many names. To confuse matters a bit more, related fields often falling under the VR moniker include “animation,” “artificial reality,” “augmented reality,” “telepresence,” and even “multimedia.” We’ll clear up the relationship between these terms in the third section of this chapter, “VR Offshoots, Variations, and Variants.”
The best definition for VR which I have come up with is: Virtual Reality produces a 3D, computer-generated experience in which one can navigate around, interact with, and be immersed in another environment.
To explain further, VR is a computer-generated parallel world in which the user is immersed in a dynamic, interactive artificial environment. “Virtual” in this sense derives from the concept of “virtual memory” in a computer which acts “as if” it is actual memory. VR provides a different reality which mimics our everyday reality. Thus, the VR world appears “as if” it is the “real world.”
We might add multi-sensory experience to our definition, but much of VR now is only visual. Some VR developers add an audio component, but it does not seem
necessary to VR’s definition. Some VR developers are also working on our sense of smell and touch, but their work is quite preliminary. These senses are much harder to mimic and refresh than visual and audio. I don’t know of anyone who is trying to build a sense of taste into VR. However, in the future, multi-sensory dimensions may be necessary to VR’s definition.
There is a primacy to the visual dimension in our lives, particularly with 3D vision. It has been estimated that vision contributes 70% of the sensory information we take in. Since we humans are primarily visual animals who see in 3 dimensions, we understand and respond to spatial 3D images much better than flat, 2D text and sketches. With 3D images like those produced in VR, we are better able to see patterns, relationships, and trends.
VR goes beyond mere 3D images to images which, like the real world, we can navigate through and interact with in real time. Rather than a predetermined path defined in an animation, the entire VR image is redrawn with each movement by the user. You can choose to see your VR “world” from any perspective. You can move around an object, see it from different heights, and even roll the world upside down. Since we can choose to break the law of gravity in VR, you can fly over objects. In some instances, if you have not chosen to have what is called collision detection in your VR world, you can walk through walls, slip under floors, and fly through ceilings. You can get lost in the world. It’s a strange experience.
Presence and Point of View
In VR you should have a sense of presence in the world as you navigate within it, though the sort of presence you should have is still open to debate. Your presence in the world should also have a point of view. Closely related to the issue of immersion, which follows, some VR gives you a first person perspective on the world in that you are looking at the world as if from your own body. Other experiences in VR are from a second person perspective. Separated from yourself, you see some representation of yourself interacting in the world. There is no one standard of presence in VR at the moment.
VR is immersive in that you are drawn into the visualization, either through a fully immersive display which cuts off all of the outside world or a less immersive means such as a computer monitor. There is debate among VR developers about how immersive VR must be. Some people contend that VR must be totally immersive with all of the outside world’s sights and sounds blocked out, most often through use of a head mounted display and ear phones. Other people suggest that VR can be experienced with glasses through which one can see the outside world as well as VR images. Still others contend that VR on a computer monitor or projected on a screen is fine.
Once again, to complicate matters, there are other means of displaying a VR experience such as booms, caves, cabs, surround screens, and even direct laser retinal displays. We’ll discuss these output devices later in this chapter. Suffice it to say that there is no easy answer to this debate. How immersive VR needs to be is open to personal opinion and preferences.
VR is interactive in that you can not only navigate through the VR world, but also influence the elements and objects within it. Often you can do such things as change colors, move objects, open or close doors, and turn lights on and off. In some instances, you can actually change structures or interact with a persona or an avatar (the electronic representation of a person or other being in VR). However, not all VR allows for these actions. Some VR programs will only allow you to change a structure (usually a complex one) from outside the world. Other programs will allow you, from inside the world, to import objects from a library of available objects outside the world.
VR attempts to operate in “real time,” though the term is open to interpretation. The ideal is to achieve a refresh rate of 30 fps (frames per second). This is the speed at which TV sets operate in the US. Films have a 24 fps frame rate. Below these frame rates, one experiences a flutter and/or relative jerkiness of motion.
My colleague, Tom Murphy, suggests that “real time” is a poor term and that we should use the term “sufficiently fast.” The acceptable frame rate is dependent upon what you are trying to achieve with your application. For some applications like architectural visualizations on a monitor screen or projected, a slower frame rate may be acceptable as it is much like a slow walk and all that you want to do is give a sense of the environment from different perspectives. However, in a military simulation or VR game using a head mounter display (HMD), you want to get as high a frame rate as possible to give a sense of reality and to limit simulator sickness caused by jerky movements.
There are other factors to consider here such as latency between your head movements and the display’s response when using a HMD. There are also the trade-offs between detail of the image and frame rate speed. I will address these factors further in the sections entitled VR Software Today and VR Hardware Today.
From these on-going debates over VR as a relatively new and developing technology, the consensus on necessary minimal characteristics for an experience to be VR seem to be that:
(1) you can navigate in a VR world within a 3D environment,
(2) with a sense of presence in the world,
(3) some degree of immersion,
(4) interactivity, and
(5) a sufficiently fast speed.