Environmental Engineering Reference
In-Depth Information
window by utilising a standard high resolution monitor. Users interact with the
environment through conventional means such as keyboards, mice and trackballs, which
can be augmented by using 3D interaction devices such as a SpaceBallä or DataGloveä.
The non-immersive systems are more economical to set up as they usually do not require
the highest level of graphics performance and without any specialized hardware
requirements. They can also be cloned on high specification Personal Computers. These are
the lowest cost VR solutions that are being employed for many virtual environment
applications. The reported drawback, however, is that they are usually outperformed by the
more sophisticated systems. They are confined within the limit of the existing 2D interaction
device and thus provide little or no sense of immersion hence of little use where the
perception of scale is an important factor. It is expected that the growing use of Virtual
Reality Modelling Reality Language (VRML), which is also being adopted as a de-facto
standard for the transfer of 3D model data and virtual worlds via the internet, should fuel
the use of non-immersive virtual environment applications. It is argued that the advantage
of VRML is in its ability to run relatively well on personal computers as opposed to many
other proprietary VR authoring tools and the growth in its use that can result in the current
trends of commercial VR software having VRML as a tool incorporated in them to explore
the commercial possibilities of desktop VR applications.
3.3 Semi-immersive virtual environments
In semi-immersive virtual environments, the viewer becomes partly but not fully immersed
in this environment. These systems borrowed considerably from technologies developed in
the flight simulation field and are a relatively new implementation of VR technology, which
often consists of a large, concave screen, projection system and monitor similar to the large
screen experiences seen at IMAX cinemas. They usually involve high end computer
graphics. A flight simulator, for an example may present a semi-immersive simulation of an
aircraft cockpit where the set up would consist of a physical display of the cockpit and chair
with three dimensional images. The trainee does not need to wear virtual reality gear such
as a data glove or head mounted display (HMD) and is still aware of the real world outside
of the virtual environment. Semi-immersive systems present a few advantages over fully
immersive systems such as a CAVE, an automatic virtual environment system, which
includes cost, ease of use and logistics. But it has its disadvantages as well which include
limited range of interaction devices and problems with multi-user applications
A semi-immersive system can be set up with a relatively high performance graphics
computing system which can be coupled with a large screen monitor, a large screen
projector system or a multiple television projection systems. They provide a greater sense of
presence than non-immersive systems and also a greater appreciation of scale. Because the
images can be of a far greater resolution than those of HMDs, semi-immersive systems
possess the ability to share the virtual experience. This has been argued to be its advantage,
especially in educational applications as it allows simultaneous experience of the virtual
environment without the need for head-mounted immersive systems. Also, stereographic
imaging can be achieved, using some type of shuttered glasses in synchronisation with the
graphics system. According to vrs.org, Shutter Glasses are Liquid Crystal Shutter (LCS)
glasses which consist of a lightweight headset with a liquid crystal lens placed over each
eye. Stereopsis works on the principle that in order to perceive depth in a scene, the
