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g2gp 17-01-2009
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Creating and Using Virtual Reality: a Guide for the Arts and Humanities #

Glossary#

3-D space ball
These devices allow users to move or rotate 3-D models by moving a sensor ball, just as a standard mouse allows users to move a cursor on a computer screen.

Animation
In virtual reality, animation is the movement of an object or the viewpoint along a pre-determined path. Animation of the viewpoint or the user's view results in a fly-through or a guided tour. The animation may be repeated in an endless loop or have a set start and finish.

API
The application program interface (API) is a method by which an application program can make requests of the computer's operating system or of another application.

Avatar
The identity of a user of a CVE is represented by an avatar, which may be cartoon-like or a more realistic human figure. All simultaneous users of a CVE have visible avatars which reflect both an individual user's movement around the world and convey communications and emotions between different users. The term avatar derives from Hindu mythology. A deity called Vishnu is believed to have visited earth nine times to curb evil. For each visit, Vishnu took a different incarnation, called an avatar.

Backward compatibility
The ability for a computer application to read files which were created in a previous version of the software. A computer is said to be backward compatible if it can run the same software as the previous model of the computer.

Behaviours
Behaviours are program scripts that are attached to objects within VRML. The scripts cause an object to act in a certain way, for example a sphere may turn from red to green. This action may be triggered by a user of the world if the behaviour is attached to an event.

BMP
BMP is a standard image format in which image data is stored as a bitmap without applying any compression.

Browser
A Web browser is a piece of software which allows access to the World Wide Web. It interprets HTML, displaying the data in an easy-to-read format. There are two distinct types of browser – graphical and non-graphical/text only. Typical graphical browsers are Netscape Navigator/Communicator and Microsoft Internet Explorer. An example of a text only browser is Lynx.

Bubble world
Environments created by manipulating 2-dimensional digital images and not by writing code which manipulates a computer's ability to display and render 3-dimensional geometry. Typically, as in Apple's Quicktime VR, a bubble world is made by taking digital photographs of the real place or space that is to be represented digitally. These are 'stitched' together into a 360 degree panorama. The user's viewpoint is in the centre of this panorama or 'bubble' and they can move around within its confines.

CAD
Computer Aided Design software is widely used by designers, surveyors, architects and others to produce 2-dimensional drawings and 3-dimensional models. For more information about CAD see the CAD: Guide to Good Practice.

Cave
Caves or sheds are projection-based virtual reality systems which use a system of display screens surrounding viewers to fill their field of vision.

CD-ROM
In computers, CD-ROM technology is both a format and system for recording, storing, and retrieving electronic information on a compact disk that is read using an optical drive. A disk can hold up to 600 megabytes of information.

Collaborative Virtual Environments (CVE).
This refers to an environment usually built in VRML (or some extension of VRML) that can be accessed by more than one user from more than one computer simultaneously. Users are made aware of each other's presence by the use of avatars and by the chat boxes which can be used to communicate with others.

Collision Detection (VR)
A program script that determines how close a user is to an object and stops their movement when they collide with the object.

CPU
The Central Proccessing Unit is the component in a computer which performs operations on data. Data are input to the CPU, processed (according to the instructions in a program) and then output. Instructions can only be carried out one at a time, thus the speed of the processor affects the speed with which the computer works. Processor speed can range from 100 Megahertz (100 million cycles per second) to 2.8 Gigahertz (2.8 billion cycles per second). Desk-top computers generally incorporate slower processors than the workstations that are used by graphics designers.

DAT (Digital Audio Tape)
A helical-scan recording method initially developed to record CD-quality sounds on high-density audio tapes. It was quickly adapted for data storage applications. While DAT cartridges are all the same size (2.1 by 2.9 by 0.4 inches), the properties of the tape inside them differ. The smaller-capacity drives use tape cartridges that can store 1.3GB to 2GB of uncompressed data, and they have typical transfer rates ranging from 183KB per second (KBps) to 366KBps. Their larger-capacity siblings support tape cartridges that store anywhere from 3GB to 4GB of uncompressed data, with typical transfer rates ranging from 366KBps to 510KBps. Many DAT drives offer some type of hardware-based data compression, which can significantly increase capacities and decrease transfer rates, depending on the type of data being stored.

Database
A generic term commonly used to describe a structured collection of data. Databases can take many forms including unstructured full text, images, maps, statistics or a mixture of data sources.

Dataglove
A glove that contains sensors which provide a means of controlling objects within the virtual world in direct response to movement of a user's hand.

Data model
The theoretical model by which data are structured. Common data models include relational, network, hierarchical and object-oriented. Data modelling is a methodology for structuring data for use in database systems.

Densitometers
A measuring device that registers the density of reflective or transparent materials.

DLT (Digital Linear Tape)
Digital Linear Tape Drive (DLT) provides a very fast (800 Kbytes per second) back-up to tape cartridges that hold either 20 gigabytes or 40 gigabytes of data and can be mounted in an automated library that holds enough cartridges to back up 5.2 terabytes of data

Dublin Core
A 15 field standard for metadata – or 'information about information'. Full details are available from: http://www.purl.oclc.org/metadata/dublin_core

DVD (Digital Versatile Disk)
This is an optical disk technology that is expected to replace the CD-ROM disk (as well as the audio compact disc) over the next few years. The digital versatile disk (DVD) holds 4.7 gigabytes of information on one of its two sides, or enough for a 133-minute movie. With two layers on each of its two sides, it will hold up to 17 gigabytes of video, audio, or other information.

Encryption
The conversion of data into a form, called a cipher, that secures against unauthorised access to data.

EPS
Encapsulated PostScript. An image-storage format that extends the PostScript page-description language to include images.

Events (VR)
An event is a program script which is attached to an object within VRML. The event triggers an action, or behaviour. For example, a script may cause a sphere to turn from red to green when a user performs a certain action. Events range from proximity sensors (users come within a certain distance to an object), to a timer (the user has been in a world for a specified amount of time) or a touch sensor (the user clicks on the object).

Facet (VR)
A facet is a planar surface of an object. Facets are generally triangular because triangles are always planar. Facets may be other shapes, as long as they are not warped in any direction and are truely planar.

Fishbowl VR
A term which refers to VR displayed and viewed on a personal, desk-top computer rather than on large projection screens or hemispheriums. The analogy is with watching a computer monitor as one would a fishbowl. Just as one expects to see a fish moving through time and space in a fishbowl, so fishbowl VR convinces us that we are watching and interacting with 3-D space 'in' the monitor. Also referred to as desk-top VR. See also Immersive/Non-immersive.

Fly-through
In virtual reality this is the movement of an object, or viewpoint, along a path that has been defined in a program script.

FTP
File Transfer Protocol. A common method for transferring files across the Internet.

GIF
Graphics Interchange Format. A bitmap graphics format from CompuServe which stores screen images economically and aims to maintain their correct colours even when transferred between different computers.

GIS
Geographic Information Systems are used to manage maps and other spatial data held in layers. GIS packages can hold data about the location and height of an object and increasingly are being used to produce two-and-a-half dimensional models of landscapes which can be animated. For more information about GIS see the GIS: Guide to Good Practice.

Greyscale
The range of shades of grey in an image. The grey scales of scanners and terminals are determined by the number of greys, or steps between black and white, that they can recognise and reproduce.

Head-Mounted Display
A VR headset that restricts the user's vision to the VR environment since it covers the eyes. These are often used in immersive VR.

Hotspots (VR)
An identified point in a bubble world or VR environment that users can activate and cause a program script to execute an event.

ICC profiles
International Color Consortium colour standards. For further information see: http://www.color.org

Image compression
These are techniques which are used to reduce the size of digital image files. Lossless compression techniques, such as those used in the GIF and TIFF formats, retain all of the original image data while still reducing the overall file size. Lossy compression techniques, such as those used in the JPG format, compress the image file by removing image details (usually those details that the eye does not see very well) and thus losing some of the original data.

Immersive/Non-Immersive
The term immersive implies that an individual is experiencing VR either with a head-mounted display or else in some other manner, such as a hemispherium, which restricts their senses and reference to the real world. Non-immersive is generally referred to as fishbowl VR or desktop VR. From a qualitative point of view the different types of VR affect how the individual experiences the VR and how far they are convinced by the experience.

Interaction
This can be divided into low-level interaction and high-level interaction. Low-level interaction in the case of VR environments involves the user navigating around the environment and experiencing the space. High-level interaction is more complex and involves behaviours and events, that is objects act in a certain way when triggered by a user.

Internet Connection
This is the connection between a personal computer and the Internet and may be by cable modems, dsl modems, ISDN line, dial-up modem, satellite link, fixed wireless connection, etc. The type of connection affects the speed with which users can download files across the Internet. Speed can range from 56 K (kilobytes per second) in a dial-up modem to 3 mbps (Megabytes per second) with the cable modems and up to 100 mpbs with ISDN lines.

Intranet
A 'private' computer network, accessible only to particular persons, usually within a distinct organisation or institution. (As opposed to the Internet, which is a publicly accessible network.)

Interoperability
The ability of disparate computer systems to interact with one another, especially databases.

IP
Internet Protocol – one of the main protocols behind the working of the Internet.

ISO film speed
The standard for quoting photographic film speeds. It relates to the film's reactivity to light.

Java
Java is an object-oriented programming language that is designed to be portable across multiple platforms. It achieves this by using a 'virtual machine' known as the Java Runtime Environment (see below). Programs developed in Java, known as applets, are compiled for the JRE rather than for a specific operating system and thus can be run on any machine.

Java enabled browser
A web-browser that incorporates a JRE into its program is known as a Java enabled browser. Both Netscape and Internet Explorer incorporated versions of the JRE. But the pace of Java language development by Sun has meant that both Netscape and Microsoft have dropped JRE from their latest browsers. Users must now install a JRE plug-in from SUN Microsystems; this plug-in enables Java applets to be run within web-browsers or run directly from the user's computer.

Java Runtime Environment (JRE)
The Java Runtime Environment is a computer program which enables Java applets to run on different operating systems or web-browsers. Sun Microsystems develop the JRE for Sun, Linux and Windows operating systems. JREs are also being developed by freelance programmers for other operating systems, and Apple develops the Mac Java Runtime (MJR)

Javascript
This is Netscape's cross-platform scripting language, used for developing Internet applications.

JPEG
JPEG (Joint Photographic Experts Group) Image Format is a standard for variable level compressed images which are commonly used for display on Web pages. JPEG produces small file sizes using a lossy data compression technique.

Landscape
This refers to the orientation of an image. Landscape describes an image which is wider than it is tall. (An image that is taller than it is wide is referred to as 'portrait'.)

Level of Detail (LOD)
The level of detail visible in an object reduces with distance. In a virtual world, Level of Detail operations involve, for example, replacing a detailed object with a less detailed version at a set distance from a viewpoint or vice versa. Detailed surface textures may also be replaced by less detailed textures. Polygonal modellers are used to produce optimised versions of objects and textures which can be used in LOD operations.

Metadata
Metadata is often described as data about data. It is information that helps a user or system to organise, access and use a resource. Metadata may serve various roles, including cataloguing and archiving, resource discovery, technical and content description.

Multi-User Environment
see Collaborative Virtual Environment

Node
This has two meanings in VR. In VRML, a node is a small piece of code which has a specific set of attributes. For example, the shape node can be either a sphere, a box, a cone or a cylinder as set out in the VRML specification. A node can also refer to a hot-spot in a bubble world that can be used to link together a series of such worlds. For example, a user can click on a hot-spot in a central bubble world and be transported into another bubble world. These might be a set of rooms in a museum, where users are able to move from room to room by clicking on hot-spots.

On-the-fly
Computer operations that develop or occur dynamically in 'real-time', rather than as the result of something that is statically predefined.

Open systems architecture
An architecture whose specifications are public. This includes officially approved standards as well as privately designed architectures whose specifications are made public by designers.

Operational specification
A definition of working parameters.

Optimisation (VR)
Optimisation is the process of improving the efficiency of a virtual world by removing any unnecessary facets that slow down the rendering of an object.

Photo-realistic
Representing an object 'as is', that is without any optical 'effects' etc. having been added.

Platform
A term that defines both the operating system of the computer and its hardware base, usually referring to the central processing unit.

Platform independent
Software or digital formats that can be used on any computer system regardless of the operating platform.

Plug-in
Plug-in applications are programs that can easily be installed and used as part of a web-browser, for example to view digital animations. See also Viewer.

PNG
Portable Network Graphics. Pronounced 'ping' The PNG format is intended to provide a portable, legally unencumbered, well-compressed, well-specified standard for lossless raster/bitmapped image files. Full details available from: http://www.eps.mcgill.ca/~steeve/PNG/png.html

Polygonal modeller (VR)
A virtual reality authoring tool or CAD software used to define facets creating 3-D objects. Polygonal modellers can also be used to edit objects or to optimise them. Some modellers automatically create less detailed versions of objects by reducing the number of facets. Optimisation tools remove any unnecessary facets that slow down the rendering of an object.

QTVR
Quick Time Virtual Reality is Apple's virtual reality format. In QTVR a panoramic image is projected onto the inside surface of a 'notional' cylinder or sphere and then viewed through an interactive window on the computer screen.

RAM
Random Access Memory, the part of a computer's memory where data are temporarily stored while being worked on.

Raster
A way of displaying spatial information as coloured grid cells. Also referred to as bitmap as effectively a map of bits is evident.

Ray tracing
A technique for adding realism to computer models by including variations in shade, colour intensity, and shadows that would be produced by having one or more light sources. Ray tracing software simulates the path of light rays as they would be absorbed or reflected by objects.

Real-time
If a computer responds in 'human time' this is considered to be real-time. For example, if a computer model moves approximately at the speed that users expect without being jerky or not rendering properly, it is considered to be real-time. As this is hard to achieve, a range of techniques is used to create an illusion of real-time movement. A different definition of real-time relates to the currency of information. This definition might apply if a user moved around a computer model and expected it to render and change instantaneously to display up-to-date information. An example might be a traffic map which users can access to see the speed of the traffic in the part of the city that they want to navigate.

Render
Adding realism to computer models, by for example applying a surface image to a geometrical frame.

Server
Computer that performs functions for other 'client' computers.

Stitching Program (VR)
A stitching program merges a set of images together to create a single large image without noticeable joins.

Storyboard
This is the process of making an outline of what a resource will look like before it is actually created. Storyboards are used by designers to organise the ideas and content used to convey a story. A high-level storyboard, in the form of a flow chart or in text, sets out events and identifies media requirements (such as photography, graphic design etc.). A graphical storyboard consists of sketches of virtual reality sequences, which may be accompanied by a script and a detailed description of how the user will interact with the content. Storyboards are modified throughout the design process.

Synthetic Environment
The military definition of a synthetic environment is a computer-based representation of the real world, usually a current or future battle space, within which any combination of 'players' may interact. The 'players' may be computer models, simulations, people or real equipment.

Textures
These are images which are applied to the surfaces of objects in virtual reality models to give the appearance of building materials or other surface details. Textures may be either photographs of real-world objects or simplified images that are created using drawing software.

Thumbnail
Low-resolution digital images, usually used for quick reference and linkage to a larger, higher quality image.

TIFF
Tagged Interchangeable File Format/TIF (PC) or TIFF (Macintosh). A widely used graphic image format.

URL
Uniform Resource Locator. A standard addressing scheme used to locate or reference files on the Internet. Used in World Wide Web documents to locate other files. A URL gives the type of resource (scheme) being accessed (e.g. gopher, ftp) and the path to the file. The syntax used is: scheme://host.domain[:port]/path filename

VDU
Visual Display Unit – a computer monitor.

Vector
A geometric way of displaying spatial information as a series of points, lines and polygons.

Viewer (VR)
Viewers or plug-ins are software programs that are used to extend the capabilities of a browser or operating system. In the case of virtual reality, viewers to enable users to see models on desk-top computers.