3D Stereo

A term commonly used for stereoscopy. This is the technique of producing images on a screen that have life-like depth by presenting slightly different images to each of the viewer's eyes. This can be done in a wide variety of ways.

3 DOF / 6 DOF

3 Degrees Of Freedom. This term is generally used in reference to position tracking systems, but also to force feedback systems. 3 DOF tracking systems generally track x, y, and z orientation. e.g. the InterTrax II. 6 DOF tracking systems track position and orientation, e.g. the Flock of Birds from Ascension.

4D Movie

A term sometimes used in reference to stereoscopic movies and movie theatre which are equipped to play a sterescopic 3D movie along with extra surprise elements such as water sprays or under-seat noises and vibrations.

3D Movie

A movie which has been shot in 3D (using two cameras for live action). An example of this kind of movie is James Cameron's Ghosts of the Abyss shown at 3D Imax cinemas.

5.1 Surround Sound

A commonly used surround sound format from Dolby comprising 5 channels of normal sound and one low frequency bass channel.

3D DVD

A DVD movie recorded in 3D. These contain the left and right stereoscopic views in the even and odd lines (fields) of the image. This is a budget way of playing back stereoscopic 3D content but has the disadvantage of being half the resolution of a DVD.

Anaglyph

An early form of stereoscopic display using red and blue glasses. This is a low cost method of stereoscopic viewing but has the disadvantage of not allowing full colour. This has now been surpassed by technologies such as passive polarising projection systems which give full colour imagery. Anaglyph was famously used for a 3D version of Jaws.

Active Stereo

A method of stereoscopic display (either projected or on a CRT monitor) utilising powered shutter glasses (e.g CrystalEyes)that function by alternately allowing each eye to see the left-eye/right-eye images in very quick succesion to create the impression of depth. The alternative to this method is passive stereo.

Autostereo(scopic)

A method of stereoscopic display in which glasses are not required. Examples of LCD screens of this type include Dimension Technologies, SeeReal and SynthaGram.

Augmented Reality

A type of virtual reality system whereby the user sees computer generated imagery superimposed over the real world. This type of system is possible with head-mounted displays such as the Trivisio ARvision in conjuction with a tracking system.

CAD

Computer Aided Design. This term is generally used to refer to a CAD package such as Catia, SolidWorks or ProEngineer.

Circular Polarisation

A type of filter used in passive stereoscopic projection rigs. This has the advantage over linear polarisation in that it allows viewers to tilt their heads to a certain degree whilst maintaining the stereoscopic effect. The disadvantage of this type of polarisation is increased cost and increased ghosting making linear polarisation generally the preferred option.

Composite Video

A commonly used type of video signal (either PAL or NTSC). This type of signal has the advantage of using a single cable but does not match the quality of component or s-video signals.

Digitising

A term used in relation to 3D, meaning the creation of a 3D model in the computer that represents as closely as possible a real object. This can be acheived with a 3D scanner.

DOF

Degrees-of-Freedom. Term used in relation to tracking and haptic force-feedback systems. See 3 DOF and 6 DOF definitions above.

DVI

Digital Video Interface. A new type of connector/interface for connecting PCs to projection and desktop screens using a digital signal.

Emitter

Term used in active stereoscopic systems to refer to the small infra-red that transmits an infrared signal to wireless shutter glasses in order to synchronise them with the alternating left and right stereoscopic images on the screen.

FOV

Field of View. This term generally refers to the perceived diagonal size of a display in degrees. It is an important attribute of any display as generally the larger FOV the display, the more immersive it is.

Ghosting

Also know as crosstalk. This is an undersirable effect in stereoscopic graphics where the left eye images can be seen by the right eye and vice versa. This leads to a breakdown of the stereoscopic effect. Different types of stereoscopic display devices exhibit different levels of ghosting.

HMD, Headset

Head-mounted Display. A display device worn on the user's head. Typically using LCD technology, examples of this display include Trivio's 3Scope, and NVIS's nVisor SX. These devices can be used in conjuction with a tracking device to create an immersive virtual reality.

HUD

Head-up display. A display device that provides an image floating in mid-air in front of the user. Typical uses include displaying information manuals and on-site data to engineers. MicroOptical's displays are a good example of this technology.

Immersive

A term used to describe a system that is designed to envelop the participant in a virtual world or experience. The amount of immersion the participant feels depends on a number of factors. Visual immersion is the most common goal. This can be done effectively using a large screen or a head-mounted display.

Interlaced

A type of video stream made up of odd and even lines (or sometimes columns). Normal TV signals (like PAL & NTSC) are interlaced signals, made up of two odd and even line images called fields. These odd and even fields can be used to store stereoscopic left and right images, a technique used on 3D DVDs, although this halves the vertical resolution of the video.

Lumens

A measure of brightness of projectors. Typical LCD projector brightness ranges from 1500 to 10,000 lumens.

Matrix Switcher

A type of video connection box with a number of input and outputs that allows completely configurable links between them. For example, one input stream may be outputted on several output channels.

NTSC

A type of interlaced video stream used primarily in North America. It is made up from 525 horizontal lines playing at 30 frames per second (or 60 fields per second).

OpenGL

Opengl is the industry standard low-level language for rendering 3D graphics in real-time.

Passive Stereo

A technique whereby 3D stereoscopic imagery is acheived by polarising the left and right images differently at source, viewed using low-cost polarising glasses. Inition's Duality range are passive stereo systems.

PAL

A type of interlaced video stream used in the UK and around the world. It is made up from 625 horizontal lines playing at 25 frames per second (or 50 fields per second).

Realtime 3D Graphics

Realtime graphics are produced on-the-fly, by a 3D graphics card. Realtime is essential if the user needs to interact with the images as in virtual reality, as opposed to watching a movie sequence.

Rear Projection

Rear projection is when images are projected from behind a screen. The advantage of this configuration is that a viewer cannot cast shadows by getting inbetween the projector and screen - particularly important when a user is interacting with images on the screen. Certain types of rigid and flexible rear projection screens can be used for stereoscopic projection.

SDK

Software development toolkit.

Silvered screen

A type of screen surface used for passive stereoscopic front projection. These screens maintain the polarisation of the light introduced by polarising filters in front of the two projector lenses.

Stereoscopic / Stereoscopy / Stereo

This is the technique of producing images on a screen that have life-like depth by presenting slightly different images to each of the viewer's eyes. This can be done in a wide variety of ways.

S-Video

Super-video, sometimes (incorrectly) called SVHS. A video signal used for PAL and NTSC video. S-Video signals comprise of separate luminance and chrominance signals - a technique which gives much better results than the composite video format which contains both luminance and chrominance in one signal.

SVGA

A computer video signal comprising of 800 pixels across and 600 pixels height.

SXGA

A computer video signal comprising of 1280 pixels across and 1024 pixels height.

Tracking

A 3D tracking system is used in virtual reality in order for the computer to track the participant's head and hands. There are many different types including optical, magnetic and ultrasonic tracking systems.

VGA

A computer video signal comprising of 640 pixels across and 480 pixels height.

XGA

A computer video signal comprising of 1024 pixels across and 768 pixels height.