As these are multiple questions, let me start with my attempt to answer the question in your text, which is already not very easy to answer - what is the exact definition of virtual reality. Maybe others can contribute too, but I don´t think there is "one" exact definition.

In general, VR can be characterized as a computer-simulation of fictional or close to real environments, with which the user can interact. There have been numerous attempts to define VR, however, many older definitions (from the nineties, where VR was becoming a popular thing) are mainly focused on technical aspects as the following examples of defining VR demonstrate:

“The illusion of participation in a synthetic environment rather than external observation of such an environment. VR relies on a three-dimensional, stereoscopic head-tracker display, hand/body tracking and binaural sound. VR is an immersive, multi-sensory experience.” (M. A. Gigante. Virtual reality: Enabling technologies, 1993.)

“The terms virtual worlds, virtual cockpits, and virtual workstations were used to describe specific projects. . . . In 1989, Jaron Lanier, CEO of VPL, coined the term virtual reality to bring all of the virtual projects under a single rubric. The term therefore typically refers to three-dimensional realities implemented with stereo viewing goggles and reality gloves.” (M. W. Krueger. Artificial reality II, volume 10. Addison-Wesley Reading (Ma), 1991.)

Today, personally I would define Virtual Reality to be as something like: "...a computer interface, which surrounds the user with sensory information (e.g. visual, auditory, etc...) and allows for interaction with a simulated environment. This in turn

provides the user with some sort of “presence” and/or “telepresence”, both of which refer to the sense of being in the simulated, computer-generated environment." For the term "presence" and what it means, I would recommend to have a look at the in my opinion great work from Mel Slater (University of Barcelona).

Of course this answer is not exhaustive, but might give you a starting point. For the current technology, it´s also not trivial to answer, because it depends on what you want to do. For industrial VR and (correct) simulation purposes I believe IC.IDO is one of the market leaders in Europe, but it might be very different for other parts of the world. For creating compelling VR experiences you can also use current game engines like Unity 3D and the Unreal Engine 4, which look fantastic in an HMD or a large screen immersive display for example. There are also many other solutions and technologies for visualizing information in terms of virtual reality. It comes down to your requirements and what you want to achieve by using virtual reality.

Hope that long wall of text does at least answer small bits of your question.

Best,

Markus

Thanks Marcus