Glossary of Terms

[A] | [B] | [C] | [D] | [E] | [F] | [G] | [H] | [I] | [J] | [K] | [L] | [M] | [N] | [O] | [P] | [Q] | [R] | [S] | [T] | [U] | [V] | [W] | [X] | [Y] | [Z]

[A]

[B]

[C]

compiler

A program that converts another program from some source language (or programming language) to machine language (object code). Some compilers output assembly language which is then converted to machine language by a separate assembler.

context data

OpenGL state information is associated with a GL graphics window, or more generally, a display context. Compiled OpenGL commands such as displaylists do not get shared across muiltiple contexts (or windows) so you will need to initialize them once per window. For example, if you were to try to call a display list created on a context that is not currently active, then your application will likely fail or do unexpected things.

This data that is only valid within its context is referred to as context-specific data.

[D]

display context

A display context is the current place graphics commands render to. For example a display context can be the window on your screen that OpenGL renders to. In more complex applications such as in VR systems, you often have multiple windows open at a time (and thus multiple display contexts to render to).

For each display context you often need to create context-specific data.

[E]

environment variable

A variable that defines an aspect of your working environment such as your home directory, editor, or printer. Such variables are set during the login/startup procedure.

edge-triggering

A term that describes the four states given to you from a button press: On, Off, Just_On, Just_Off. An input device can either use the edge-triggering method or the normal on/off button method.

[F]

functor

Something that performs an operation or a function.

[G]

graphical user interface (GUI)

The use of pictures rather than just words to represent the input and output of a program. A program with a GUI runs under some windowing system (e.g., the X Window System, Microsoft Windows, Acorn RISC OS, NEXTSTEP). The program displays certain icons, buttons, dialogue boxes, etc. in its windows on the screen. The user controls it mainly by moving a pointer on the screen (typically controlled by a mouse) and selecting certain objects by pressing buttons on the mouse while the pointer is pointing at them.

GUI

See graphical user interface.

[H]

[I]

[J]

[K]

[L]

[M]

matrix

A rectangular array of numeric or algebraic quantities set out by rows and columns and subject to mathematical operations.

mutex

A mutual exclusion object that allows multiple threads to synchronize access to shared resources. A mutex has two states: locked and unlocked. Once a mutex has been locked by a thread, other threads attempting to lock it will block. When the locking thread unlocks (releases) the mutex, one of the blocked threads will lock (acquire) it and proceed with its execution. A mutex is thus a binary semaphore.

mutual exclusion

In computer science: a collection of techniques for sharing resources so that different manipulators of the resources do not conflict and cause unwanted interactions.

[N]

[O]

operating system (OS)

The low-level software which handles the interface to peripheral hardware, schedules tasks, allocates storage, and presents a default interface to the user when no application program is running.

[P]

platform

Specific computer hardware, as in the phrase ``platform-independent''. It may also refer to a specific combination of hardware and operating system and/or compiler, as in ``this program has been ported to several platforms''. It is also used to refer to support software for a particular activity, as in ``This program provides a platform for research into routing protocols.'' In the VR Juggler documentation, we refer to the platform as the combination of hardware and operating system.

proxy

To act in place of another. In VR Juggler a proxy is a handle or pointer to something else, typically an actual input device. For example in an application a user would access an input device through a vjDeviceInterface—behind this proxy is a vjDeviceProxy—and behind this is a vjInput (the actual device). The vjDeviceInterface is a doubly proxies the vjInput device since it is a proxy to the vjDeviceProxy.

[Q]

quaternion

In mathematics: an expression that is the sum of a real number and a vector and that contains four terms, one real and three imaginary. Also, the quotient of two vectors, or of two directed right lines in space, considered as depending on four geometrical elements, and as expressible by an algebraic symbol of quadrinomial form. For more information, refer to the following documents:

• Game Developer Magazine, Feb 1998, pages 34-42
• Advanced Animation and Rendering Techniques, pages 363-365
• ``Quaternion Calculus for Animation'', K. Shoemake, SIGGRAPH Proceedings Vol. 19, Number 3, 1985

[R]

[S]

semaphore

In computer science: a method for restricting access to shared resources in a multithreaded environment invented by Dijkstra. Operations on semaphores can be either test or increment. A semaphore is free if its value is greater than or equal to 1. It is locked if its value is 0.

smart pointer

Objects that encapsulate C++ pointers. They are a very powerful concept that can provide many features over standard pointers include safety in dereferencing. A smart pointer is accessed using the dereference operator (->).

surface window

A Juggler Surface Window can be put into stereo, right eye, or left eye display modes. Most interesting is the stereo mode since it requires special hardware to display stereo, and creates the most immersive experience.

simulator window

A VR Juggler Simulator Window is special because it simulates the VR system. It can show the all active user's head and wand position and orientation as well as the display surfaces themselves. The simulator window is nice for debugging tracking systems, and to visually see the Display Surface configuration.

[T]

thread

In computer science: a portion of a program that can run independently and concurrently with other portions of the same program.

triple-buffered data

It is sometimes wise to use triple buffered data, so that one thread is not writing to the data as it is being read by a different thread.

tracker

A tracker is a positional device used to tell where something is in space.

Some background: In a PC desktop environment the mouse is usually the only tracking system available, with tracking done in 2 space (x,y coordinates). This kind of device is usually not popularly desired by immersive VR enthusiests, but is quite effective in entertainment applications such as Id Software's Quake (the very popular keyboard/mouse combination is even sold as an add-on to console systems such as SegaDreamcast and Playstation2).

In VR a tracker gives you position information usually in 3 space (x,y,z coordinates). Generally the VR tracker is attached to the body or held in the hand to let the computer know where you are in space thereby allowing the VR system to "track" you. Some popular VR tracking devices are the Wand or Glove, both of which typically use both digital (button) input and positional (tracking) input.

Almost always tracking input is used in conjunction with button input, as seen in many devices such as Wand, Glove, and even the Mouse.

[U]

[V]

vector

In mathematics: a quantity, such as a velocity, completely specified by a magnitude and a direction; a one-dimensional array; an element of a vector space.

VR

Virtual Reality

VR Juggler

An extremely scalable and flexible virtual reality toolkit.

Virtual Platform

A piece of software that allows you to write a virtual reality application that can be scaled to to any system configuration.

[W]

[X]

[Y]

[Z]

Sources: Dictionary.com