The name of the default Window Manager. See also window manager.

See login account.

The setting used when you create a new object in IRIS Showcase. For example, when you select blue from the color palette and Helvetica from the text gizmo, you change the active setting. Graphics objects you draw are blue; text you type is Helvetica.

The portion of the video signal having the chrominance or luminance information; also, all video lines not in the vertical blanking signal that contain the chrominance or luminance information. See also chrominance, composite video, horizontal blanking, luminance, and video waveform.

The only window that recognizes input (activity) from the keyboard and mouse; only one window is active at a time. Make a window active by placing the cursor within its boundaries.

See network administrator, system administrator

A rendering technique that assigns to pixels the color of the primitive being rendered, regardless of whether that primitive covers all of the pixel's area or only a portion of the pixel's area. This results in jagged edges, or jaggies. In video systems, aliasing results when an image is sampled that contains frequency components above the Nyquist limit for the sampling rate. See also Nyquist limit.

This IRIS Showcase command lets you line up objects. You can align objects to one another, to a grid, or sequentially.

The fourth color component of a pixel, specifying its opacity, translucency, or transparency. The alpha component is typically used to control color blending, and in video systems, is treated as a separate signal output. By convention, OpenGL alpha corresponds to the notion of opacity rather than transparency, meaning that an alpha value of 1.0 implies complete opacity, and an alpha value of 0.0 complete transparency.

Overlaying one image on another so that some of the underlying image may or may not be visible. See also keying.

A bank of memory that stores alpha values; the values are 8 bits per pixel.

A register that stores an alpha value.

See alpha.

A rendering technique that assigns pixel colors based on the fraction of the pixel's area that's covered by the primitive being rendered. Antialiased rendering reduces or eliminates the jaggies that result from aliased rendering.

Average Picture Level, with respect to blanking, during active picture time, expressed as a percentage of the difference between the blanking and reference white levels. See also blanking level.

Clipping of primitives against planes in eye coordinates; the planes are specified by the application using glClipPlane().

In video systems, an unnatural or artificial effect that occurs when the system reproduces an image; examples are aliasing, pixellation, and contouring.

ASCII text is characters onlynot the size, the font, the style, the color, or the format of the characters. When you save a file as ASCII text, you save only the characters.

The ratio of the width to the height of an image. For example, the standard aspect ratio for television is 4:3. Maintaining the original aspect ratio of an image prevents it from being distorted.

The user who is automatically logged in to the system each time it is powered up.

See face.

The portion of the horizontal pedestal that follows the horizontal synchronizing pulse. In a composite signal, the color burst is located on the back porch, but is absent on a YUV or GBR signal. See also blanking level, video waveform.

To copy a set of files and directories from your hard disk to a tape or other storage media.

A tape that contains a copy of a set of files and directories that are on your hard disk. A full backup tape contains a copy of all files and directories, including IRIX, that are on your hard disk.

Occasionally, a part of a hard disk on a workstation may lose its ability to store information. When this happens, the piece of disk that has malfunctioned is known as a bad block. IRIX provides a facility to allow your workstation to skip over bad sections of disk and continue to use the rest of the disk.

The speed (calculated as bits per second) at which the computer sends information to a serial device, such as a modem or terminal. A part of line settings. See also line setting

A component videotape format developed by Sony® that uses a Y/R-Y/B-Y video signal and 1/2-inch tape.

Advanced form (Superior Performance) of Betacam using special metal tape and offering longer recording time (90 minutes instead of 30 minutes) and superior performance.

Binary digit. A state variable having only two possible values: 0 or 1. Binary numbers are constructions of one or more bits.

A rectangular array of bits. Also, the primitive rendered by the glBitmap() command, which uses its bitmap parameter as a mask.

A region of memory that contains the pixels representing an image. The pixels are arranged in the sequence in which they are normally scanned to display the image.

A rectangular array of bits mapped one-to-one with pixels. The framebuffer is a stack of bitplanes.

Active video signal that has only black in it. The black portion of the video signal, containing color burst. See also color burst.

In the active video portion of the video waveform, the voltage level that defines black. See also horizontal blanking and video waveform.

The signal level at the beginning and end of the horizontal and vertical blanking intervals, typically representing zero output
(0 IRE). See also video waveform and IRE units.

Combining two color components into one, usually as a linear interpolation between the two components. The alpha value helps determine how the components are combined. See also alpha; for video-related terms, see also key and frame.

A group of digits, characters, or words that are held in one section of an input/output medium and handled as a unit. Within the IRIX filesystem, a block of disk space consists of 512 bytes.

The boot block is the first block of each filesystem. A filesystem block is 512 bytes. The boot block is read for instructions when the system is booted. These instructions are for the hardware and are not used by the operating system.

The networking protocol that provides the service for booting a computer over a network connection. BOOTP is essential to diskless workstation operation.

A window with no title bar or borders.

In the horizontal blanking part of the video signal, the portion between the end of the horizontal sync pulse and the beginning of the color burst. See also horizontal blanking and video waveform.

Vertical synchronizing pulses in the center of the vertical interval. These pulses are long enough to be distinguished from other pulses in the signal; they are the part of the signal actually detected by vertical sync separators.

In PAL signals, a four-field burst blanking sequence that assures that burst phase is the same at the end of each vertical interval.

A group of bitplanes that store a single component (such as depth or green) or a single index (such as the color index or the stencil index). Sometimes the red, green, blue, and alpha buffers together are referred to as the color buffer, rather than the color buffers.

See color burst.

The ability of the output subcarrier to be locked to input subcarrier, or of output to be genlocked to an input burst.

In the RS-170A standard, burst phase is at field 1, line 10; in the European PAL standards, it is at field 1, line 1. Both define a continuous burst waveform to be in phase with the leading edge of sync at these points in the video timing. See also vertical blanking interval, and video waveform.

On a mouse, a button is a switch you press with a finger. In a window on your screen, a button is a labeled rectangle you click using the cursor and mouse.

One of the color difference signals used on the NTSC and PAL systems, obtained by subtracting luminance (Y) from the blue camera signal (B). This signal drives the horizontal axis of a vectorscope. Color mixture is close to blue; phase is 180 degrees opposite of color sync burst; bandwidth is 0.0 to 0.5 MHz. See also luminance, R-Y signal, Y signal, and Y/R-Y/B-Y.

God's programming language.

Type C, or 1-inch reel-to-reel videotape machine; an analog composite recording format still used in some broadcast and postproduction applications.

Chrominance; the color portion of the signal. For example, the Y/C video format used for S-VHS has separate Y (luminance) and C (chrominance) signals. See also chrominance.

Component Analog Video; a generic term for all analog component video formats, which keep luminance and chrominance information separate. D1 is a digital version of this signal. See also component video.

The digital interface standard developed by the CCIR (Comité Consultatif International de Radiodiffusion, or International Radio Consultative Committee) based on component color encoding, in which the luminance and chrominance (color difference) sampling frequencies are related in the ratio 4:2:2: four samples of luminance (spread across four pixels), two samples of CR color difference, and two samples of CB color difference. The standard, also referred to as 4:2:2, sets parameters for both 525-line and 625-line systems.

A flat metallic disc that contains information you can view and copy onto your own hard disk; you cannot change or add to its information. CD-ROM is short for compact-disc: read-only memory.

A computer network where a central server controls services and information; the server is maintained by one or more individuals called network administrators. On a centralized network that uses NIS, this server is called the NIS master, and all other systems on the network are called NIS clients. See also distributed network, network administrator, NIS, NIS client, NIS domain, and NIS master.

To press the left mouse button to bring up a pop-up menu, move the cursor to highlight the command you want, then release the button.

See chrominance.

Overlaying one video source on another by choosing a key color. For example, if chroma keying is on blue, video source A might show through video source B everywhere the color blue appears in video source B. A common example is the TV weather reporter standing in front of the satellite weather map. The weather reporter, wearing any color but blue, stands in front of a blue background; keying on blue shows the satellite picture everywhere blue appears. Because there is no blue on the weatherperson, he or she appears to be standing in front of the weather map.

A 3.58 MHz (NTSC) or 4.43 MHz (PAL) subcarrier signal for color in television. SECAM uses two frequency-modulated color subcarriers transmitted on alternate horizontal lines; SCR is 4.406 MHz and SCB is 4.250 MHz.

In an image reproduction system, a separate signal that contains the color information. Black, white, and all shades of gray have no chrominance and contain only the luminance (brightness) portion of the signal. However, all colors have both chrominance and luminance.

Chrominance is derived from the I and Q signals in the NTSC television system and the U and V signals in the PAL television system. See also luminance.

Also called the chroma, or C, signal. The high-frequency portion of the video signal (3.58 MHz for NTSC, 4.43 MHz for PAL) color subcarrier with quadrature modulation by I (R-Y) and Q (B-Y) color video signals. The amplitude of the C signal is saturation; the phase angle is hue. See also color subcarrier, hue, and saturation.

A group of all printers of a given type. You define the types of printers. For example, all printers in a given room might be grouped as a class, or all laser printers might be a class.

To hold the mouse still, then press and immediately release a mouse button.

The computer from which OpenGL commands are issued. The computer that issues OpenGL commands can be connected via a network to another computer that executes the commands, or commands can be issued and executed on the same computer. See also server.

An application that has connected to the video daemon to perform video requests.

The main memory (where program variables are stored) of the client computer.

The coordinate system that follows transformation by the projection matrix and that precedes perspective division. View-volume clipping is done in clip coordinates, but application-specific clipping is not.

Elimination of the portion of a geometric primitive that's outside the half-space defined by a clipping plane. Points are simply rejected if they are outside. The portion of a line or of a polygon that's outside the half-space is eliminated, and additional vertices are generated as necessary to complete the primitive within the clipping half-space. Geometric primitives and the current raster position (when specified) are always clipped against the six half-spaces defined by the left, right, bottom, top, near, and far planes of the view volume. Applications can specify optional application-specific clipping planes to be applied in eye coordinates.

A test pattern used by video engineers to determine the quality of a video signal, developed by the Society of Television and Motion Picture Engineers (SMPTE). The test pattern consists of equal-width bars representing black, white, red, green, blue, and combinations of two of the three RGB values: yellow, cyan, and magenta. These colors are usually shown at 75% of their pure values.

The segment of the horizontal blanking portion of the video signal that is used as a reference for decoding color information in the active video part of the signal. The color burst is required for synchronizing the phase of 3.58 MHz oscillator in the television receiver for correct hues in the chrominance signal.

In composite video, the image color is determined by the phase relationship of the color subcarrier to the color burst. The color burst sync is 8 to 11 cycles of 3.58 MHz color subcarrier transmitted on the back porch of every horizontal pulse. The hue of the color sync phase is yellow-green.

Also called burst and burst flag. See also color subcarrier and video waveform.

Signals used by color television systems to convey color information so that the signals go to zero when the picture contains no color; for example, unmodulated R-Y and B-Y, I and Q, U, and V.

In NTSC and S-Video, a two-frame sequence that must elapse before the same relationship between line pairs of video and frame sync repeats itself. In PAL, the color-frame sequence consists of four frames.

A single value that represents a color by name, rather than by value. OpenGL color indices are treated as continuous values (for example, floating-point numbers) while operations such as interpolation and dithering are performed on them. Color indices stored in the framebuffer are always integer values, however. Floating-point indices are converted to integers by rounding to the nearest integer value.

An OpenGL context is in color index mode if its color buffers store color indices, rather than red, green, blue, and alpha color components.

A table of index-to-RGB mappings that's accessed by the display hardware. Each color index is read from the color buffer, converted to an RGB triple by lookup in the color map, and sent to the monitor.

The collection of colors you can use in IRIS Showcase.

A space defined by three color components, such as R, G, and B.

A portion of the active portion of a composite video signal that carries color information, referenced to the color burst. The color subcarrier's amplitude determines saturation; its phase angle determines hue. Hue and saturation are derived with respect to the color burst. The color subcarrier's frequency is defined as 3.58 MHz in NTSC and 4.43 MHz in PAL. See also color burst.

Process that improves the accuracy of extracting color and brightness portions of the signal from a composite video source.

Options that let you specify how you want to run an IRIX command. See the man page for a command for a list of the available command line options.

Opposite hue and phase angle from a primary color. Cyan, magenta, and yellow are complementary colors for red, green, and blue, respectively.

A single, continuous (for example, floating-point) value that represents an intensity or quantity. Usually, a component value of zero represents the minimum value or intensity, and a component value of one represents the maximum value or intensity, though other normalizations are sometimes used. Because component values are interpreted in a normalized range, they are specified independent of actual resolution. For example, the RGB triple (1, 1, 1) is white, regardless of whether the color buffers store 4, 8, or 12 bits each.

Out-of-range components are typically clamped to the normalized range, not truncated or otherwise interpreted. For example, the RGB triple (1.4, 1.5, 0.9) is clamped to (1.0, 1.0, 0.9) before it's used to update the color buffer. Red, green, blue, alpha, and depth are always treated as components, never as indices.

A color encoding method for the three color signals—R, G, and B; Y, I, and Q; or Y, U, and V—that make up a color image. See also RGB, YIQ, and YUV.

A video signal in which luminance and chrominance are sent as separate components to yield a signal with a higher color bandwidth than that of composite video. Examples of component video signals are:

- RGB (basic signals generated from a camera)

- YIQ (used by the NTSC broadcasting standard)

- Y/R-Y/B-Y (used by Betacam and M-II recording formats and SECAM broadcasting standard)

- YUV (subset of Y/R-Y/B-Y used by the PAL broadcasting standard)

Separating these components yields a signal with a higher color bandwidth than that of composite video.

Figure Gl-3 depicts video signals for one horizontal scan of a color-bar test pattern. The RGB signals change in relation to the individual colors in the test pattern. When a secondary color is generated, a combination of the RGB signals occurs. Because only the primary and secondary colors are being displayed at 100% saturation, the R, G, and B waveforms are simply on or off. For more complex patterns of color, the individual R, G, and B signals are varying amplitudes in the percentages needed to express that particular color.

See also chrominance, composite video, luminance, RGB, YIQ, and YUV.

A color encoding method or a video signal that contains all of the color, brightness, and synchronizing information in one signal. The chief composite television standard signals are NTSC, PAL, and SECAM. See also NTSC, PAL, and SECAM.

Nonconvex. See convex.

A test that you run to make sure a particular device (such as the keyboard, mouse, or a drive) is set up and working properly.

A system file you can change to customize the way your system behaves. Such files are also called customization files.

Hardware at the end of a cable that lets you fasten the cable to an outlet, port, or another connector.

The window that appears as a stowed icon each time you log in; IRIX reports all status and error messages to this window.

A complete set of OpenGL state variables. Note that framebuffer contents are not part of OpenGL state, but that the configuration of the framebuffer is.

A polygon is convex if no straight line in the plane of the polygon intersects the polygon more than twice.

The smallest convex region enclosing a specified group of points. In two dimensions, the convex hull is found conceptually by stretching a rubber band around the points so that all of the points lie within the band.

In n-dimensional space, a set of n linearly independent vectors anchored to a point (called the origin). A group of coordinates specifies a point in space (or a vector from the origin) by indicating how far to travel along each vector to reach the point (or tip of the vector).

A process or program that requires a great deal of calculation or operation on the part of the CPU is considered CPU-intensive. For example, a program that calculates the value of pi to one million places is considered CPU-intensive. The speed of the CPU bus and the clock rate of the CPU itself are the limiting factors on the speed of a CPU-intensive program.

Also known as cross-color, hanging dots, dot crawl; moving colors on stationary objects. This undesirable artifact is caused by high bandwidth luminance information misinterpreted as color information. Hanging dots are a by-product of the comb filters (used to help separate the color and brightness information) found in most modern television receivers. This artifact can be reduced or eliminated by using S-Video or a component video format.

A type of transition in which one video clip is faded down while another is faded up.

The process of eliminating a front face or back face of a polygon so that it isn't drawn.

A matrix that transforms coordinates in one coordinate system to coordinates of another system. There are three current matrices in OpenGL: the modelview matrix transforms object coordinates (coordinates specified by the programmer) to eye coordinates; the perspective matrix transforms eye coordinates to clip coordinates; the texture matrix transforms specified or generated texture coordinates as described by the matrix. Each current matrix is the top element on a stack of matrices. Each of the three stacks can be manipulated with OpenGL matrix-manipulation commands.

A window coordinate position that specifies the placement of an image primitive when it's rasterized. The current raster position, and other current raster parameters, are updated when glRasterPos() is called.

The directory within the filesystem in which you are currently located when you are working in a shell window.

The small red arrow on the screen that echoes the movements of the mouse. It changes shape depending on its location on the screen.

To remove objects or text from the page and place them in a cut buffer.

Digital recording technique for component video; also known as CCIR 601, 4:2:2. D1 is the best choice for high-end production work, where many generations of video are needed. D1 can be an 8-bit or 10-bit signal. See also CCIR 601.

Digital recording technique for composite video. As with analog composite, the luminance and chrominance information is sent as one signal. A D2 VTR offers higher resolution and can make multiple generation copies without noticeable quality loss, because it samples an analog composite video signal at four times the subcarrier (using linear quantization), representing the samples as 8-bit digital words. D2 is not compatible with D1.

Developed by Panasonic, a 1/2-inch tape version of D2. More often called DX.

Programs that are run automatically by the system for a specific purpose. For example, timed, the time daemon checks the current time on the system against a master clock on another system.

A magnetic tape from which you can read and to which you can copy audio and digital information.

A signal that a modem carrier tone has been detected. The DCD signal is sent on pin 8 of an RS-232 cable.

A type of serial interface. DCE devices transmit data on pin 3 and receive on pin 2. See null modem.

A type of serial interface. DTE devices transmit data on pin 2 and receive on pin 3. The serial ports for IRIS workstations and servers are configured as DTE. Most terminals are also configured as DTE. See null modem.

A signal that the terminal is ready to give and receive information. This signal is sent on pin 9 of a 9-pin cable and pin 20 on an RS-232 cable.

Hardware or software that converts, or decodes, a composite video signal into the various components of the signal. For example, to grab a frame of composite video from a VHS tape deck and store it as an RGB file, it must be decoded first. Several Silicon Graphics video options have on-board decoders.

The printer to which the system directs a print request if you do not specify a printer when you make the request. You set the default printer using the Print Manager.

A set of behaviors that Silicon Graphics, Inc., specifies on every system. You can later change these specifications, which range from how your screen looks to what type of drive you want to use to install new software. For example, when you run IRIS Showcase, the Master gizmo opens by default. You can change the default settings using the Preferences gizmo.

To permanently remove an object from an IRIS Showcase page. Once you've removed them, you can't retrieve objects by choosing Paste.

Generally refers to the z window coordinate.

A rendering technique that assigns color based on distance from the viewpoint.

The printer where a file is printed.

A series of tests that check all hardware components of your system.

The ASCII terminal connected to the port labeled 1 on the I/O panel of a server. Error messages and diagnostics information produced by the power-on diagnostics appear on the screen of this terminal.

An extra password required by a workstation from users who are accessing the system through a modem connected to an external phone line. This password is required before the login process can begin. It provides an added level of security against intruders.

A container in the filesystem in which you can store other directories and files.

The window you see when you open a file folder (directory) icon. You control its display through the Directory View menu and WorkSpace Preferences form.

A program or process that requires large amounts of data to be read from or written to the hard disk is considered disk-intensive. For example, a program that saves its entire working buffer to the disk once per second is considered disk-intensive. The limiting factor on the speed of disk-intensive programs is the time required for the disk access.

A section of the hard disk that stores information about the contents of the rest of the disk.

Any disk (hard, CD-ROM, or floppy) can access either because it is physically attached to your workstation with a cable, or it is available over the network using NFS. See also NFS.

The percentage of space on your disk that contains information.

A named list of OpenGL commands. Display lists are always stored on the server, so display lists can be used to reduce network traffic in client-server environments. The contents of a display list may be preprocessed, and might therefore execute more efficiently than the same set of OpenGL commands executed in immediate mode. Such preprocessing is especially important for computing intensive commands such as glTexImage().

A computer network that has no automated central control of services or information. Each system's administrator must work with the network administrator to keep each system's network information up to date. See also centralized network.

A technique for increasing the perceived range of colors in an image at the cost of spatial resolution. Adjacent pixels are assigned differing color values; when viewed from a distance, these colors seem to blend into a single intermediate color. The technique is similar to the halftoning used in black-and-white publications to achieve shades of gray.

A group of hosts on a network whose hostnames have the same suffix. See also NIS domain.

The common suffix found in all hostnames that are in the same domain on a network. See also NIS domain.

OpenGL contexts with both front and back color buffers are double-buffered. Smooth animation is accomplished by rendering into only the back buffer (which isn't displayed), then causing the front and back buffers to be swapped.

To hold the mouse still, then press and release it twice, very rapidly. When you double-click an icon, it opens into a window; when you double-click the Window menu button (in the upper left corner of a window), the window closes.

To press and hold down a mouse button, then move the mouse. This drags the cursor to move icons or to highlight menu items.

In the context of the Video Library, a target or consumer of video signals.

The area in which you draw or place objects.

A hardware device that lets you access information on various forms of media, such as hard, floppy, and CD-ROM disks, and magnetic tapes.

See SCSI address.

The icon onto which you drag files when you want to delete them. The dumpster icon appears in your home directory and the WorkSpace window.

In IRIS Showcase, you edit an object when you want to alter its individual elements—letters and words in a Text object, and points in a Graphics object.

The process in which data is examined, created, and modified. In video, the part of the postproduction process in which the finished videotape is derived from raw video footage. Animation is a subset of editing.

A single component or index.

Device that combines the R, G, and B primary color video signals into hue and saturation for the C portion of a composite signal. Several Silicon Graphics video options have on-board encoders.

When you set all the preferences for the shell, commonly used applications, the window manager, and the system in general, together those settings are called the environment. Usually, when speaking of the environment, only the shell settings are included.

You can save your IRIS Showcase files as EPS and import them into other programs that accept EPS files.

Pulse of one half the width of the horizontal sync pulse, transmitted at twice the rate of the horizontal sync pulse, during the portions of the vertical blanking interval immediately before and after the vertical sync pulse. The equalizing pulse makes the vertical deflection start at the same time in each interval, and keeps the horizontal sweep circuits in step during the portions of the vertical blanking interval immediately before and after the vertical sync pulse.

The OpenGL process of generating object-coordinate vertices and parameters from previously specified Bézier equations.

Exceptional or noteworthy condition produced during video processing, such as loss of sync, dropping of frames or fields, and synchronization with other applications.

A term applied to use of the video data stream and controls on a pathway. A pathway in exclusive-use mode is available for writing of controls only to the client that requested the exclusive use, yet any application may read the controls on that pathway.

An OpenGL command is executed when it's called in immediate mode or when the display list that it's a part of is called.

To use NFS software to make all or part of your filesystem available to other users and systems on the network.

A piece of hardware attached to the workstation with a cable.

The coordinate system that follows transformation by the modelview matrix and that precedes transformation by the projection matrix. Lighting and application-specific clipping are done in eye coordinates.

One side of a polygon. Each polygon has two faces: a front face and a back face. Only one face or the other is ever visible in the window. Whether the back or front face is visible is effectively determined after the polygon is projected onto the window. After this projection, if the polygon's edges are directed clockwise, one of the faces is visible; if directed counterclockwise, the other face is visible. Whether clockwise corresponds to front or back (and counterclockwise corresponds to back or front) is determined by the OpenGL programmer.

To modify the opacity and/or volume of a clip. A faded-up clip is unaffected, a clip faded down to 50% has 50% less opacity or volume, and a faded-down clip is completely transparent or completely turned off.

An area in a window in which you can type text.

One of two (or more) equal parts of information in which a frame is divided in interlace scanning. A vertical scan of a frame carrying only its odd-numbered or its even-numbered lines. The odd field and even field make up the complete frame. See also frame and interlace.

A filter that corrects flicker by averaging pixel values across successive fields. See also flicker.

The blanking signals at the end of each field, used to make the vertical retrace invisible. Also called vertical blanking. See also vertical blanking and vertical blanking interval.

A container in which you store information such as text, programs, or images you create using an application.

See filesystem.

A hierarchical data structure that holds and organizes files in directories. Filesystems are designed so that users can find their files and organize them conveniently. Directories can contain other directories and files; files cannot contain directories or other files. The root (/) directory is at the top of the hierarchy.

To process a clip with spatial or frequency domain methods. Each pixel is modified by using information from neighboring (or all) pixels of the image. Filter functions include blur (low-pass) and crisp (high-pass).

Refers to coloring a primitive with a single, constant color across its extent, rather than smoothly interpolating colors across the primitive. See Gouraud shading.

The effect caused by a one-pixel-deep line in a high-resolution graphics frame that is output to a low-resolution monitor, because the line is in only one of the alternating fields that make up the frame. This effect can be filtered out by field averaging. See also field and frame.

A rendering technique that can be used to simulate atmospheric effects such as haze, fog, and smog by fading object colors to a background color based on distance from the viewer. Fog also aids in the perception of distance from the viewer, giving a depth cue.

A group of graphical character representations usually used to display strings of text. The characters may be roman letters, mathematical symbols, Asian ideograms, Egyptian hieroglyphics, and so on.

A window that contains buttons you click and/or editable fields you fill in.

The host that forwards mail from one domain to another.

Fragments are generated by the rasterization of primitives. Each fragment corresponds to a single pixel and includes color, depth, and sometimes texture-coordinate values.

The result of a complete scanning of one image. In television, the odd field (all the odd lines of the frame) and the even field (all the even lines of the frame) make up the frame. In motion video, the image is scanned repeatedly, making a series of frames.

All the buffers of a given window or context. Sometimes includes all the pixel memory of the graphics hardware accelerator.

A condition on the digitized video signal where the digitizing is stopped and the contents of the signal appear frozen on the display or in the buffer. Sometimes used to capture the video data for processing or storage.

Signal cycles per second.

Placing of harmonic frequencies of C signal midway between harmonics of horizontal scanning frequency Fh. Accomplished by making color subcarrier frequency exactly 3.579545 MHz. This frequency is an odd multiple of H/2.

See face.

The portion of the video signal between the end of active video and the falling edge of sync. See also back porch, horizontal blanking, and video waveform.

The view volume warped by perspective division.

Color mixture close to green, with a bandwidth 0.0 MHz to 0.5 MHz. Usually formed by combining B-Y and R-Y video signals.

A function applied to colors stored in the framebuffer to correct for the nonlinear response of the eye (and sometimes of the monitor) to linear changes in color-intensity values.

Synchronizing with another video signal serving as a master timing source. The master timing source can be a composite video signal, a video signal with no active video (only sync information), or, for video studio, a device called house sync. When no master sync is available, VideoFramer, for example, can be set to “free run” (or standalone) mode, so that it becomes the master timing device to which other devices sync. See also line lock.

The object-coordinate vertices and parameters that describe an object. Note that OpenGL doesn't define a syntax for geometric models, but rather a syntax and semantics for the rendering of geometric models.

Geometric model.

A point, a line, or a polygon.

IRIS Showcase groups sets of related commands and tools into gizmos. For example, all the tools that control paragraph formatting are in the Text Ruler gizmo. You access gizmos from the Gizmos menu.

Smooth interpolation of colors across a polygon or line segment. Colors are assigned at vertices and linearly interpolated across the primitive to produce a relatively smooth variation in color. Also called smooth shading.

An object you create using one of the 14 drawing tools available in IRIS Showcase.

Monochrome or black-and-white, as in a monitor that does not display color.

Rows of uniformly spaced vertical and horizontal dots you see in the IRIS Showcase drawing area. You can align objects to a grid.

A collection of users who can set more relaxed permissions on files owned by one another.

Each pixel of an image in client memory is represented by a group of one, two, three, or four elements. Thus, in the context of a client memory image, a group and a pixel are the same thing.

Number of complete horizontal lines, including trace and retrace, scanned per second.

A plane divides space into two half-spaces.

The protocol that controls the flow of information between a workstation and a printer. A hardware handshake uses only cable wires and pins to control the flow. A software handshake (also called xon-xoff flow control) uses a combination of pins, wires, and software.

When a new filename is linked to an existing file, the link made by default is a hard link. A hard link must be within the same filesystem as the original file. See symbolic link.

High-definition television. Though there is more than one proposal for a broadcast standard for HDTV, most currently available equipment is based on the 1125/60 standard, that is, 1125 lines of video, with a refresh rate of 60 Hz, 2:1 interlacing (same as NTSC and PAL), and aspect ratio of 16:9 (1920 x 1035 viewable resolution), trilevel sync, and 30 MHz RGB and luminance bandwidth.

An 8 mm recording format developed by Sony; accepts composite and S-Video signals.

To change the color of an item on the screen by positioning the cursor over it (locate-highlight) or by positioning the cursor over it and pressing a mouse button.

The directory into which IRIX places you each time you log in. It is specified in your login account; you own this directory and, typically, all its contents.

A set of n+1 coordinates used to represent points in n-dimensional projective space. Points in projective space can be thought of as points in euclidean space together with some points at infinity. The coordinates are homogeneous because a scaling of each of the coordinates by the same nonzero constant doesn't alter the point to which the coordinates refer. Homogeneous coordinates are useful in the calculations of projective geometry, and thus in computer graphics, where scenes must be projected onto a window.

The period when the electron beam is turned off, beginning when each scan line finishes its horizontal path (scan) across the screen.

Also known as the horizontal retrace interval, the period when a scanning process is moving from the end of one horizontal line to the start of the next line. This portion of the signal is used to carry information other than video information. See also video waveform.

The portion of the horizontal blanking part of the video signal composed of the sync pulse together with the front porch and breezeway; that is, horizontal blanking minus the color burst. See also video waveform.

The lowest portion of the horizontal blanking part of the video signal; it provides a pulse for synchronizing video input with output. Also known as h sync. See also horizontal blanking and video waveform.

Any system connected to the network.

The name that uniquely identifies each host (system) on the network.

An optional, alternate hostname for a host (system) on the network.

See hue-saturation-intensity.

Hue-saturation-value. See hue-saturation-intensity.

The designation of a color in the spectrum, such as cyan, blue, magenta. Sometimes called tint on NTSC television receivers. The varying phase angles in the 3.58 MHz (NTSC) or 4.43 MHz (PAL) C signal indicate the different hues in the picture information.

A tristimulus color system based on the parameters of hue, saturation, and intensity (luminance). Also referred to as HSI or HSV.

A circular series of line settings such as different baud rates.

Color video signal transmitted as amplitude modulation of the 3.58 MHz C signal (NTSC). The hue axis is orange and cyan. This signal is the only color video signal with a bandwidth of 0 to 1.3 MHz.

A small picture that represents a stowed or closed file, directory, application, or IRIX process.

A rectangular array of pixels, either in client memory or in the framebuffer.

See bitplane.

A bitmap or an image.

Manipulating an image by changing its color, brightness, shape, or size.

Execution of OpenGL commands when they're called, rather than from a display list. No immediate-mode bit exists; the mode in immediate mode refers to usage of OpenGL, rather than to a specific bit of OpenGL state.

To insert another file into IRIS Showcase. You can insert ASCII text files, images, 3D models, PICT files, and other IRIS Showcase files.

A single value that's interpreted as an absolute value, rather than as a normalized value in a specified range (as is a component). Color indices are the names of colors, which are dereferenced by the display hardware using the color map. Indices are typically masked, rather than clamped, when out of range. For example, the index 0xf7 is masked to 0x7 when written to a 4-bit buffer (color or stencil). Color indices and stencil indices are always treated as indices, never as components.

Plural of index.

An inode is a 128-byte data structure that the filesystem uses to store information about a file. The information in an inode includes the owner and access permissions, the size of the file, its file type, and the location of the information on the hard disk. There is one inode per file in the filesystem. The maximum number of files in a filesystem is limited by the number of inodes in that filesystem.

Only one window at a time recognizes mouse movement and typing. The window that does is said to have the input focus.

The software tool for installing system software, software options, and maintenance releases from Silicon Graphics, Inc.

A technique that uses more than one vertical scan to reproduce a complete image. In television, the 2:1 interlace used yields two vertical scans (fields) per frame: the first field consists of the odd lines of the frame, the other, the even lines. See also field and frame.

The number that uniquely identifies each host (system) on the network.

A scale for measuring analog video signal levels, normally starting at the bottom of the horizontal sync pulse and extending to the top of peak white. Blanking level is 0 IRE units and peak white level is 100 IRE units (700 mv). An IRE unit equals 7.14 mv (+100 IRE to -40 IRE = 1v). IRE stands for Institute of Radio Engineers, a forerunner of the IEEE.

Silicon Graphics' proprietary graphics library, developed from 1982 through 1992. OpenGL was designed with IRIS GL as a starting point.

Any graphics workstation manufactured by Silicon Graphics, Inc.

Silicon Graphics, Inc.'s, version of the UNIX operating system. See system software.

Tasks that IRIX carries out to keep the system running correctly or to complete an explicit command. Each process has a unique process ID number.

Artifacts of aliased rendering. The edges of primitives that are rendered with aliasing are jagged rather than smooth. A near-horizontal aliased line, for example, is rendered as a set of horizontal lines on adjacent pixel rows, rather than as a smooth, continuous line.

The text editor that comes as a standard utility on every IRIS system.

To line up text with the left and right margins.

A standard unit for measuring the information storage capacity of disks and memory (RAM and ROM); 1024 bytes make one kilobyte
(1 kB).

Combining proportional amounts of two frames, pixel by pixel, with optional opacity. This process resembles taking two panes of glass with images on them and placing one pane on top of the other. The opacity of the top pane determines the parts of the bottom pane that show. Usually, keying is a real-time continuous process, as in the “over the shoulder” graphics in TV news programs. The alpha component of each pixel, which defines its opacity, determines how the images are combined. Combining images based on the alpha component is often called alpha keying or luma keying. See also compositing and mixing.

To start up an application, often by double-clicking an icon.

The amount of space between lines of text or between paragraphs. Leading is measured in points. Each point is 1/72nd of an inch.

The portion of the video waveform after active video, between the sync threshold and the sync pulse. See also video waveform.

A light on a piece of hardware that indicates status or error conditions.

Signal amplitude.

The process of computing the color of a vertex based on current lights, material properties, and lighting-model modes.

A straight region of finite width between two vertices. (Unlike mathematical lines, OpenGL lines have finite width and length.) Each segment of a strip of lines is itself a line.

The result of a single pass of the sensor from left to right across the image.

The blanking signal at the end of each horizontal scanning line, used to make the horizontal retrace invisible. Also called horizontal blanking.

The number of horizontal scans per second, normally 15,734.26 times per second for NTSC color systems. The line frequency for the PAL 625/50H system is 15,625 times per second.

Input timing derived from the horizontal sync signal, and implying that the system clock (the clock being used to sample the incoming video) is an integer multiple of the horizontal frequency and that it is locked in phase to the horizontal sync signal. See also video waveform.

A set of line characteristics, such as expected rate of transmission (baud rate).

The process of combining a group of signals through addition or subtraction; for example, RGB signals into luminance and chrominance signals.

A mechanism for associating one piece of information with another. In IRIS Showcase you can link an object to another object, page, program, or file.

A pointer to a file or directory that exists in another location in the filesystem. When you make a linked copy of a file, you are not creating another instance of the file; you are creating another location from which you can access the original file.

Video delivered at a nominal frame rate appropriate to the format.

The physical workstation whose keyboard and mouse you are using. All hardware connected to that workstation, and all software that resides on that hardware or its removable media, are also part of your local work area.

An IRIS Showcase command that prevents you from accidentally moving or editing an object.

To give the system your login name so you can start a session on the IRIS system.

To end a session on the IRIS system.

A logical volume is a number of areas on one or more hard disks that the system considers as one filesystem. The fact that the areas of disk space are not contiguous is hidden from the user. See also striping.

A database of information about each user that, at the minimum, consists of login name, user ID, and home directory.

A name that uniquely identifies a user to the system.

The window you see after powering on the system, before you can access files and directories. The window contains one icon for each login account on the system.

See luminance.

The perceived brightness of a surface. Typically refers to a weighted average of red, green, and blue color values that gives the perceived brightness of the combination. For video systems, luminance is the video signal that describes the amount of light in each pixel. See also chrominance and Y.

A second-generation recording format based on a version of the Y/R-Y/B-Y video signal. Developed by Panasonic, MII is also marketed by other video manufacturers. Though similar to Betacam, it is nonetheless incompatible.

A software release that contains bug fixes to system software and software options. Occasionally, a maintenance release contains feature enhancements or support for new hardware.

An online document that describes how to use a particular IRIX command.

Numerical lookup of pixel data that modifies each pixel without using neighboring pixels. This large category of video editing functions includes clip/gain, solarization, and histogram equalization.

Plural of matrix. (See indices.)

A two-dimensional array of values. OpenGL matrices are all 4×4, though when they are stored in client memory they're treated as 1×16 single-dimension arrays.

The process of converting analog color signals from one tristimulus format to another, for example, RGB to YUV. See also tristimulus color system.

A standard unit for measuring the information storage capacity of disks and memory (RAM and ROM); 1024 kilobytes make one megabyte (1 MB).

A program is said to be memory intensive if it uses a great deal of memory and performs frequent changes to the data in memory so that the system cannot swap out the data to allow other processes to use the memory. For example, word processing applications with many open files use a great deal of memory.

A list of operations or commands that the IRIS can carry out on various objects on the screen.

To shrink a window and display it as a stowed icon on the screen. Minimized applications continue to run.

In video editing, combining two clips frame by frame, pixel by pixel. Usually, a linear interpolation between the pixels in each clip is used, with which you can, for example, perform a cross-fade. Other operations include averaging, adding, differencing, maximum (non-additive mix), minimum, and equivalence (white where equal, else black). See also compositing and keying.

The characteristics of the terminal interface. A part of line settings. The TTY line and the terminal must be working in the same mode before communication can take place.

The 4×4 matrix that transforms points, lines, polygons, and raster positions from object coordinates to eye coordinates.

The device that displays the image in the framebuffer.

A technique that simulates what you get on a piece of film when you take a picture of a moving object, or when you move the camera when you take a picture of a stationary object. In animations without motion blur, moving objects can appear jerky.

To make a filesystem that is stored on a local or remote disk resource accessible from a specific directory on your workstation.

The directory on your workstation from which you access information that is stored on a local or remote disk resource. Most mount point directories are left empty because information in that directory is unavailable while the filesystem is mounted there.

A hardware device you use to communicate with windows and icons. You move the mouse to move the cursor on the screen, and you press its buttons to initiate operations. An optical mouse must always be on the mouse pad for the IRIS system to interpret its movements; a mechanical mouse works on any clean, flat surface.

For an optical mouse, this is the rectangular, metallic surface that reads the movements of the mouse. For a mechanical mouse, this is a clean, soft rectangular surface that makes the mouse's track ball roll efficiently.

A file you create and view on your workstation screen.

A test pattern consisting of sets of vertical lines with closer and closer spacing; used for testing horizontal resolution of a video system.

A system that can run several processes (such as running applications, printing files, and updating files) simultaneously.

A system that several users can work on simultaneously and maintain private files.

A connection between two or more computers that allows each to transfer data to and from the others.

A group of computers and other devices (such as printers) that can all communicate with one another electronically to transfer and share information.

The individual(s) responsible for setting up, maintaining, and troubleshooting the network, and for supplying setup information to system administrators of each system.

A networking software option that lets you access files and directories that reside on the disks of other workstations as if they resided on a local disk in your own workstation. NFS stands for Network File System.

A networking software option that lets you control network information and services from a central server called the NIS master. NIS stands for Network Information Service. See also centralized network, NIS client, NIS domain, and NIS master.

A system on a centralized network— other than the NIS master—that runs NIS. The NIS client receives services and information from the NIS master.

The unique name of a network (or subnetwork) that runs NIS. All hostnames in the NIS domain have the NIS domain name as their suffix.

The server that stores the complete database of information about all the hosts (systems) and users on a centralized NIS network. The NIS master periodically updates host information on all other systems on the network (NIS clients); its user information is always available to every host. The network administrator is responsible for setting up, maintaining, and troubleshooting the NIS master.

A polygon is nonconvex if there exists a line in the plane of the polygon that intersects the polygon more than twice.

A three-component plane equation that defines the angular orientation, but not position, of a plane or surface.

Divide each of the components of a normal by the square root of the sum of their squares. Then, if the normal is thought of as a vector from the origin to the point (nx', ny', nz'), this vector has unit length.

factor = (nx² + ny² + nz²)^1/2

nx' = nx / factor

ny' = ny / factor

nz' = nz / factor

Same as normal.

A form that appears on screen when the system requires that you confirm an operation you just requested, or when an error occurs.

A color television standard or timing format encoding all of the color, brightness, and synchronizing information in one signal. Used in North America, most of South America, and most of the Far East, this standard is named after the National Television Systems Committee, the standardizing body that created this system in the U.S. in 1953. NTSC uses a total of 525 horizontal lines per frame, with two fields per frame of 262.5 lines each. Each field refreshes at 60 Hz (actually
59.94 Hz).

A type of cable that reverses the wires on which information is sent and received. Some devices receive and send information on opposite wires, and you must switch these wires to use the devices properly.

Non-Uniform Rational B-Spline. A common way to specify parametric curves and surfaces.

The highest frequency of input signal that can be correctly sampled without aliasing. The Nyquist limit is equal to half of the sampling frequency.

An object-coordinate model that's rendered as a collection of primitives.

Coordinate system prior to any OpenGL transformation.

Everything you place on the page in an IRIS Showcase file is considered an object—the graphics you draw, text you type, and images and 3D models you import.

In the context of a video signal, the relative coordinates from the upper left corner of the video image where signal sampling begins.

An IRIS Showcase setting that determines whether objects are opaque or see-through.

To double-click an icon, or to select an icon then choose “Open” from a menu to display a window that contains the information that the icon represents.

OpenGL is a graphics library—a software interface to graphics hardware—based on IRIS GL and developed by Silicon Graphics with an industry consortium known as the OpenGL Architecture Review Board. This interface consists of about 120 distinct commands (plus associated constants and variables), which you use to specify the objects and operations needed to produce interactive 3D applications. The term OpenGL can also refer to the hardware-independent specification for the OpenGL graphics library.

Nonperspective projection, as in some engineering drawings, with no foreshortening.

To scan a little beyond the display raster area of the monitor so that the edges of the raster are not visible. Television is overscanned; computer displays are underscanned.

The user who created a particular file or directory and who can specify which other users of the system can access the file.

Each page in an IRIS Showcase file can have a separate page of notes associated with it. You create page notes using the Page Notes command.

A color television standard or timing format developed in West Germany and used by most other countries in Europe, including the United Kingdom but excluding France, as well as Australia and parts of the Far East. PAL uses a total of 625 horizontal lines per frame, with two fields per frame of 312.5 lines per frame. Each field refreshes at 50 Hz. PAL encodes color differently from NTSC. PAL stands for Phase Alternation Line or Phase Alternated by Line, by which this system attempts to correct some of the color inaccuracies in NTSC. See also NTSC and SECAM.

The elements between carriage returns. A paragraph can be one character, one word, or several pages.

The leading, tab settings, margin settings, and justification for a paragraph. In an IRIS Showcase file, you control these with the Text Ruler gizmo.

A hardware device that requires a parallel cable connection to communicate with the workstation.

An outlet on the workstation to which you connect external parallel devices.

A value passed as an argument to an OpenGL command. Sometimes one of the values passes by reference to an OpenGL command.

A relative term that refers to a directory that contains another directory. If directory A contains directory B, then A is the parent directory of B.

A combination of letters and/or numbers that only you know that allows you access to a system. A password is an optional element of your login account. If you specify a password for your account, you must type it after you type your login name before the system lets you access files and directories.

A list of directories the system searches when trying to find a file or run a program. You can add directories to and delete directories from your path.

The list of directories that leads you from the root (/) directory to a specific file or directory in the filesystem.

In the Video Library, a connection of sources and drains that provide useful processing of video signals. Pathways have controls and video streams. Pathways can be locked for exclusive use, and are the target of events generated during video processing. See also exclusive use and event.

The collection of patterns that you can use in IRIS Showcase.

See setup and video waveform.

A hardware device that adds more functionality to the basic workstation, such as a tape drive. See also external device.

The information attached to each directory and file that specifies which users can access it and to what degree.

A system setting that specifies the default permissions that the system assigns to newly created files and directories. The owners of those files and directories can later change the permissions.

The division of x, y, and z by w, carried out in clip coordinates.

An IRIS Showcase command that prevents you from accidentally moving an object.

Picture element. Either the smallest addressable spatial element of the computer screen, or the smallest reproducible element in analog video. A pixel can have red, blue, and green color values, an alpha component, and other information associated with it. (Pixels are referred to as having a color component even if they're gray-scale or monochrome.) The bits at location (x, y) of all the bitplanes in the framebuffer constitute the single pixel (x, y). In OpenGL window coordinates, each pixel corresponds to a 1.0x1.0 screen area. The coordinates of the lower left corner of the pixel named x,y are (x, y), and of the upper right corner are (x+1, y+1). See also alpha value and component video.

A two-dimensional piece of memory, any number of bits deep. See also bitmap.

An exact location in space, which is rendered as a finite-diameter dot.

A unit for measuring font size and leading. One point is 1/72nd of an inch.

A near-planar surface bounded by edges specified by vertices. Each triangle of a triangle mesh is a polygon, as is each quadrilateral of a quadrilateral mesh. The rectangle specified by glRect*() is also a polygon.

To bring to the foreground, that is, to the top of the stack, a window or object that is in the background, or lower in the stack. Windows on the screen and objects in the IRIS Showcase drawing area can overlap one another. You can pop a window so it appears on top of other windows; you can pop an object so it appears on top of other objects. See push.

An outlet to which you attach cable connectors.

The processes that occur before release of the finished video product, including editing, painting (2D graphics) production, and 3D graphics production.

The cable that connects the workstation to a grounded electrical outlet.

To turn off the power switches on the workstation chassis and the monitor. You should power off the system only after using the system shutdown procedure. See shut down.

To turn on the power switches on the workstation chassis and the monitor.

Red, green, and blue. Opposite voltage polarities are the complementary colors cyan, magenta, and yellow.

A point, a line, a polygon, a bitmap, or an image. (Note: Not just a point, a line, or a polygon!)

A tool that you use to set up printer software and monitor jobs that you send to the printer. You access it through either the System toolchest or the System Manager, where it is called the Printer tool.

The 4×4 matrix that transforms points, lines, polygons, and raster positions from eye coordinates to clip coordinates.

The interface for communicating with the system after it is powered up, but before it is booted up and running IRIX.

A character or word that the system displays in an IRIX shell that indicates the system is ready to accept commands. The default prompt for regular user accounts is %; the default prompt for the root account is #.

To put to the background, that is, lower in the stack, a window or object that is in the foreground, or the top of the stack. Windows on the screen and objects in the IRIS Showcase drawing area can overlap each other. You can push a window so it hides behind other windows; you can push an object so it appears below other objects. See pop.

The color video signal that modulates 3.58 MHz C signal in quadrature with the I signal. Hues are green and magenta. Bandwidth is 0.0 MHz to 0.5 MHz. See also C signal, I signal, YC, and YIQ.

A polygon with four edges.

The magnitude of the error introduced in a signal when the actual signal is between levels, resulting from subdividing a video signal into distinct increments, such as levels from 0 to 255.

A list of print jobs waiting to be printed on a particular printer.

To stop running an application.

A color difference signal obtained by subtracting the luminance signal from the red camera signal. It is plotted on the 90 to 270 degree axis of a vector diagram. The R-Y signal drives the vertical axis of a vectorscope. The color mixture is close to red. Phase is in quadrature with B-Y; bandwidth is 0.0 MHz to 0.5 MHz. See also luminance, B-Y (B minus Y) signal, Y/R-Y/B-Y, and vectorscope.

The scanning pattern for television display; a series of horizontal lines, usually left to right, top to bottom. In NTSC and PAL systems, the first and last lines are half lines.

A logical or arithmetic operation on a pixel value.

To convert a projected point, line, or polygon, or the pixels of a bitmap or image, to fragments, each corresponding to a pixel in the framebuffer. Note that all primitives are rasterized, not just points, lines, and polygons.

A quadrilateral whose alternate edges are parallel to each other in object coordinates. Polygons specified with glRect*() are always rectangles; other quadrilaterals might be rectangles.

The process of causing two frames to coincide exactly. In component video cameras or displays, the process of causing the three color images to coincide exactly, so that no color fringes are visible.

A workstation you can access across the network; it is not physically connected to your workstation. All hardware connected to that workstation, and all software that resides on that hardware or its removable media, are also part of that remote work area.

Conversion of primitives specified in object coordinates to an image in the framebuffer. Rendering is the primary operation of OpenGL—it's what OpenGL does.

A physical button on the workstation that, when pressed, cuts off then immediately restores power to the workstation. Pressing the reset button does not turn off power to the option slot devices. Never press the reset button while IRIX is running, unless all attempts to shut down the system using software fail. See also shut down.

Number of horizontal lines in a television display standard; the higher the number, the greater a system's ability to reproduce fine detail.

To copy files that once resided on a hard disk from another disk or a tape back onto the hard disk.

Red, green, blue—the basic component set used by graphics systems and some video cameras in which a separate signal is used for each primary color.

The technical specification for NTSC color television. Often (incorrectly) used to refer to an RGB signal that is being sent at NTSC composite timings, for example, a Silicon Graphics computer set to output 640 x 480. The timing is correct to display on a television, but the signal is still split into red, green and blue components. This component signal would have to go through an encoder to yield a composite signal (RS-170A format) suitable for display on a television receiver.

Red, Green, Blue, Alpha.

An OpenGL context is in RGBA mode if its color buffers store red, green, blue, and alpha color components, rather than color indices.

The standard IRIX login account reserved for use by the system administrator. This account's home directory is the root (/) directory of the filesystem; the user of the root account has full access to the entire filesystem (that is, can change and delete any file or directory). The user of this account is sometimes referred to as the superuser.

The directory at the top of the filesystem hierarchy.

To read the value of a signal at evenly spaced points in time; to convert representational data to sampled data (that is, synthesizing and rendering).

The number of times per second (measured in kHz, where
1 kHz = 1000 times per second) the system reads the file when outputting audio. The greater the sampling rate, the larger the file and the better the quality of the audio output.

Color intensity; zero saturation is white (no color) and maximum saturation is the deepest or most intense color possible for that hue. In signal terms, saturation is determined by the ratio between luminance level and chrominance amplitude. See also hue.

To change the size of an image.

To convert an image to an electrical signal by moving a sensing point across the image, usually left to right, top to bottom.

A scheme is a pre-packaged collection of colors and fonts that users can apply to application windows. Having all applications on a workstation use schemes allows users to conveniently customize their environment. The schemes are designed with an eye to effective use of color, taking into account both usability and aesthetic considerations. Multiple schemes are provided to address issues such as red-green colorblindness, monochrome X-terminals, and user preference for light or dark text. A user changes the scheme for the desktop simply by selecting the new scheme from a control panel.

The portion of the monitor that displays information.

A number from one to seven that uniquely identifies a SCSI device to a system. No two SCSI devices that are physically connected to the same workstation can have the same SCSI address.

A cable that connects a SCSI device to a SCSI port on a workstation.

A hardware device that uses the Small Computer System Interface (SCSI) protocol to communicate with the system. Hard disk, floppy disk, CD-ROM, and tape drives are all SCSI devices.

Sequentiel Couleur avec Memoire, the color television system developed in France and used there as well as in eastern Europe, the Near East and Mideast, and parts of Africa and the Caribbean.

To position the cursor over an icon then click the (left) mouse button. Once an icon is selected, it is the object of whatever operation you select from a menu.

A method of aligning objects in IRIS Showcase that lets you create uniform spacing between the bottom of one object and the top of another or the right edge of one object and the left edge of another.

A hardware device that requires a serial cable connection to communicate with the workstation.

An outlet on the workstation to which you connect external serial devices.

The computer on which OpenGL commands are executed. This might differ from the computer from which commands are issued. See client.

A system that other systems on the network access to use its disk space, software, or services.

The person who is responsible for keeping the server system up and running. This person is often also a site administrator.

The difference between the blackest level displayed on the receiver and the blanking level. A black level that is elevated to 7.5 IRE instead of being left at 0.0 IRE is the same as the lowest level for active video. Because the video level is known, this part of the signal is used for black-level clamping circuit operation. Setup is typically used in the NTSC video format and is typically not used in the PAL video format; it was originally introduced to simplify the design of early television receivers, which had trouble distinguishing between video black levels and horizontal blanking. Also called pedestal. See also video waveform.

The process of interpolating color within the interior of a polygon, or between the vertices of a line, during rasterization.

A window into which you type IRIX commands. The syntax of the commands depends on the type of shell you are using, such as the C shell or Bourne shell.

A program that issues and interprets a sequence of IRIX commands.

A cable with a protective covering that reduces the possibility of interference with radio, television, and other devices.

To change the order in which windows are stacked on the screen.

To safely close all files, log out, and bring the workstation to a state where you can safely power it off. Choose “System Shutdown” from the System toolchest menu to do this.

A small printed circuit board with several chips that contain additional megabytes of random-access memory (RAM).

OpenGL contexts that don't have back color buffers are single-buffered. You can use these contexts for animation, but take care to avoid visually disturbing flashes when rendering.

A matrix that has no inverse. Geometrically, such a matrix represents a transformation that collapses points along at least one line to a single point.

The person responsible for maintaining systems and the network at a site. A site is the area covered by the local network of systems.

An artifact usually caused by mid-frequency distortions in an analog system that results in the vertical edges of the picture spreading horizontally.

A signal specified by the Society of Motion Picture and Television Engineers for facilitating videotape editing; this signal uniquely identifies each frame of the video signal. Program originators use vertical blanking interval lines 12 through 14 to store a code identifying program material, time, frame number, and other production information.

A software product from Silicon Graphics, Inc., other than the standard system software that comes on your system disk.

In the context of the Video Library, a provider of video input signals.

A generic term for a directory or program that holds and meters jobs or data for future use. A spool directory is typically a temporary holding place for data that is bound for another place. For example, the printing command lp(1) uses spooling to dispatch each print job when the previous one is complete.

The SASH is a minimum-functionality operating system that allows you to access files and install software. Typically, the SASH is used to install the IRIX operating system.

A workstation that is not connected to a network.

The electrical discharge resulting from the accumulation of electric charge on an insulated body. When your body touches metal parts (including printed circuit boards) of computer equipment, there is the potential for you to feel an electrical shock (electrostatic discharge, or ESD) which could damage the equipment. To prevent this, always wear a wrist strap when working with internal parts of a workstation.

A one- or two-dimensional binary pattern that defeats the generation of fragments where its value is zero. Line stipples are one-dimensional and are applied relative to the start of a line. Polygon stipples are two-dimensional and are applied with a fixed orientation to the window.

The method of minimizing disk access time when creating logical volumes. On a striped volume, the workstation lays out the filesystem in stripes and allocates information alternately between the stripes. The principle at work is that the seek time for the disks is shorter because successive read and write operations will take place on different stripes and a different head will be used for each read or write operation. See logical volume.

A portion of a video signal that carries a specific signal, such as color. See also color subcarrier.

A unit derived from a pixel by using a filter for sizing and positioning.

The second (512-byte) block of each filesystem. It provides information about the size of the filesystem and a map to the free space on the disk.

An alternate name for the user of the root login account. See also system administrator.

Video format in which the Y (luminance) and C (chrominance) portions of the signal are kept separate. Also known as YC.

When a workstation is running many programs at once, it might run short of available memory. When this happens, sections of program that are not immediately being executed are written out to a special area of the disk, where they can be easily retrieved. That area of disk is known as “swap space” and the action of moving pages of program in and out is known as “swapping” or “paging.”

When a new filename is linked to an existing file with the ln -s command, the link generated is “symbolic.” Symbolic links can exist across filesystem boundaries. The drawback to symbolic links is that not all programs can follow the link back to the original file, as with a “hard link.” See hard link.

The part of the television video signal that ensures that the display scanning is synchronized with the broadcast scanning. See also video waveform.

A vertical or horizontal pulse (or both) that determines the display timing of a video signal. Composite sync has both horizontal and vertical sync pulses, as well as equalization pulses. The equalization pulses are part of the interlacing process.

The lowest part of the horizontal blanking interval, used for synchronization. See also video waveform.

All the hardware and software that makes up an IRIS workstation or server.

The tasks associated with setting up, maintaining, and troubleshooting a networked or standalone IRIS system.

The person responsible for setting up, maintaining, and troubleshooting an IRIS system. The system administrator uses the root login account to perform most administrative tasks. See superuser.

When the IRIX operating system fails and the system does not accept keyboard or mouse input.

The physical disk that contains the standard IRIX operating system software—the software that makes your workstation run.

A set of tools used by the system administrator to set up and manage an IRIS system. You access the System Manager through the System toolchest.

See dialup password.

The standard IRIX operating system software and Silicon Graphics tools that come on the system disk and on the tape or CD-ROM that you use in the event of a system crash.

The toolchest in the upper left-hand corner of the screen labeled System. You can start system tools such as IRIS WorkSpace and System Manager using its menu.

The standard networking software included in the system software.

A one-page file that gets inserted on each new page you add. Templates help regulate the format of your documents.

A display and keyboard, or a printer and keyboard, for entering programs and data to a computer and for receiving output from a computer

Selectable settings that define the way a terminal operates.

To send a signal through a transmission line accurately, there must be an impedance at the end that matches the impedance of the source and of the line itself. Amplitude errors, frequency response, and pulse distortions and reflections (ghosting) occur on a line without proper termination. Video is a 75 Ohm system; therefore a 75 Ohm terminator of .5% to .25% accuracy must be installed at the end of the signal path.

Reduction of a portion of an analytic surface to a mesh of polygons, or of a portion of an analytic curve to a sequence of lines.

A texture element. A texel is obtained from texture memory and represents the color of the texture to be applied to a corresponding fragment.

A Text object is a block of text you create using one of IRIS Showcase's text tools.

A one- or two-dimensional image that's used to modify the color of fragments produced by rasterization.

The process of applying an image (the texture) to a primitive. Texture mapping is often used to add realism to a scene. As an example, you could apply a picture of a building facade to a polygon representing a wall.

The 4×4 matrix that transforms texture coordinates from the coordinates that they're specified in to the coordinates that are used for interpolation and texture lookup.

Applying images to 3D objects to give additional realism to displayed renderings.

In a digital circuit, the signal level that is specified as the division point between levels used to represent different digital values. For example, the sync threshold is the level at which the leading edge of sync begins. See also video waveform.

Analog artifacts caused by nonuniform motion of videotape or of the tape head drum. Time-base errors usually cause horizontal display problems, such as horizontal jitter.

See SMPTE time code.

Frame-by-frame alignment of all video inputs to one sync pulse, so that all frames start at the same time. This alignment is necessary because cable length differences cause unequal delays. See time-base errors.

The window that contains the five toolchests. It appears in the upper left corner of the screen.

A device that converts a component video signal to a different component video signal, for example, RGB to Y/R-Y/B-Y, or D1 to RGB.

A microphone, video camera, or other device that can convert sounds or images to electrical signals.

A warping of space. In OpenGL, transformations are limited to projective transformations that include anything that can be represented by a 4×4 matrix. Such transformations include rotations, translations, (nonuniform) scalings along the coordinate axes, perspective transformations, and combinations of these.

A polygon with three edges. Triangles are always convex.

A system of transmitting and reproducing images that uses three color signals, for example, RGB, YIQ, and YUV.

An abbreviation for teletypewriter, the term covers the area of access between the IRIX system and peripheral devices, including the system console.

The physical wire through which access to the computer is made. See port.

One of the chrominance signals of the PAL color television system, along with V. Sometimes referred to as B-Y, but U becomes B-Y only after a weighting factor of 0.493 is applied. The weighting is required to reduce peak modulation in the composite signal.

Sony trademark of its 3/4-inch composite videotape format. SP U-Matic is an improved version using metal tape.

To scan a television screen so that the edges of the raster are visible. See also overscan.

A multiuser, multi-tasking operating system from AT&T on which Silicon Graphics Inc.'s, IRIX operating system is based.

To make a filesystem that is accessible from a specific directory on your workstation temporarily inaccessible. See mount.

Hardware that you add to the basic IRIS system that increases performance, such as additional memory (SIMMs) or faster graphics boards.

A number that uniquely identifies a user to the system.

One of the chrominance signals of the PAL color television system, along with U. Sometimes referred to as R-Y, but V becomes R-Y only after a weighting factor of 0.877 is applied. The weighting is required to reduce peak modulation in the composite signal.

A specialized oscilloscope that demodulates the video signal and presents a display of R-Y versus B-Y for NTSC (V and U for PAL). Video engineers use vectorscopes to measure the amplitude (gain) and phase angle (vector) of the primary (red, green, and blue) and the secondary (yellow, cyan, and magenta) color components of a television signal.

A point in three-dimensional space.

The portion of the video signal that is blanked so that the vertical retrace of the beam is not visible.

The blanking portion at the beginning of each field. It contains the equalizing pulses, the vertical sync pulses, and vertical interval test signals (VITS). Also the period when a scanning process is moving from the lowest horizontal line back to the top horizontal line.

Plural of vertex. See indices.

Video signal amplitude.

See drain.

The signal from a video device, such as a camera, VCR, or other scanning image sensor.

The main components of the video waveform are the active video portion and the horizontal blanking portion. Certain video waveforms carry information during the horizontal blanking interval.

The origin of either the eye- or the clip-coordinate system, depending on context. (For example, when discussing lighting, the viewpoint is the origin of the eye-coordinate system. When discussing projection, the viewpoint is the origin of the clip-coordinate system.) With a typical projection matrix, the eye-coordinate and clip-coordinate origins are at the same location.

The volume in clip coordinates whose coordinates satisfy the three conditions:

-w ≤ x ≤ w

-w ≤ y ≤ w

-w ≤ x ≤ w

Geometric primitives that extend outside this volume are clipped.

In the active video portion of the video waveform, the 1.0-volt (100 IRE) level. See also video waveform.

A character, usually an asterisk (*), that you use alone to specify all files and directories that are available, or with a few other letters to specify a group of files and directories that have a common element in their names. For example, to specify all files and directories that begin with the letters “ch”, you would type: ch*

A subregion of the framebuffer, usually rectangular, whose pixels all have the same buffer configuration. An OpenGL context renders to a single window at a time.

A portion of the screen that you can manipulate that contains text or graphics.

When referring to line segments or polygon edges, window-aligned implies that these are parallel to the window boundaries. (In OpenGL, the window is rectangular, with horizontal and vertical edges). When referring to a polygon pattern, window-aligned implies that the pattern is fixed relative to the window origin.

The coordinate system of a window. It's important to distinguish between the names of pixels, which are discrete, and the window-coordinate system, which is continuous. For example, the pixel at the lower left corner of a window is pixel (0, 0); the window coordinates of the center of this pixel are (0.5, 0.5, z). Note that window coordinates include a depth, or z, component, and that this component is continuous as well.

The system program that draws and controls windows. It lets you create and manipulate windows — move them, resize them, and close them.

A representation of an object that contains line segments only. Typically, the line segments indicate polygon edges.

The main window for working with icons and customizing your view of the filesystem. You place files and directories from all over the filesystem here for easy access; placing them in the WorkSpace does not change their actual location in the filesystem.

The physical hardware that contains the CPU and graphics boards, a system disk, and a power supply. You connect it to a monitor, keyboard, and mouse to configure a working system. It is also sometimes referred to as the chassis.

A window system used by many of the systems on which OpenGL is implemented. GLX is the name of the OpenGL extension to the X Window System.

A protocol that uses a combination of hardware and software signals to control the flow of information between a workstation and a printer. It is also referred to as a software handshake.

Luminance, corresponding to the brightness of an image. See also luminance and Y/R-Y/B-Y.

A color space (color component encoding format) based on YIQ or YUV. Y is luminance, and the two chroma signals (I and Q or U and V) are combined into a composite chroma called C, resulting in a two-wire signal. C is derived from I and Q as follows:

C - I cos(2\xb9 fsct) + Q sin(2\xb9 fsct)

where fsc is the subcarrier frequency. YC-358 is the NTSC version of this luminance/chrominance format; YC-443 is the PAL version. Both are referred to as S-Video formats.

A color space (color component encoding format) used in decoding, in which Y is the luminance signal and I and Q are the chrominance signals. The two chrominance signals I and Q (in-phase and quadrature, respectively) are two-phase amplitude-modulated. The I component modulates the subcarrier at an angle of 0 degrees, and the Q component modulates it at 90 degrees. The color burst is at 33 degrees relative to the Q signal.

The amplitude of the color subcarrier represents the saturation values of the image; the phase of the color subcarrier represents the hue value of the image.

Y = 0.299R + 0.587G + 0.114B
I = 0.596R - 0.275G - 0.321B
Q = 0.212R - 0.523G + 0.311B

A name for the YUV color component encoding format that summarizes how the chrominance components are derived. Y is the luminance signal and R-Y and B-Y are the chrominance signals. R-Y (red minus Y) and B-Y (blue minus Y) are the color differences, or chrominance components. The color difference signals R-Y and B-Y are derived as follows:

Y = 0.299R + 0.587 + 0.114B

Y/R-Y/B-Y has many variations, just as NTSC and PAL do. All component and composite color encoding formats are derived from RGB without scan standards being changed. The matrix (amount of red, green, and blue) values and scale (amplitude) factors can differ from one component format to another (YUV, Y/R-Y, B-Y, SMPTE Y/R-Y, B-Y).

A color space (color component encoding format) used by the PAL video standard, in which Y is the luminance signal and U and V are the chrominance signals. The two chrominance signals U and V are two-phase amplitude-modulated. The U component modulates the subcarrier at an angle of 0 degree, but the V component modulates it at 90 degrees or 180 degrees on alternate lines. The color burst is also line-alternated at +135 and -135 degrees relative to the U signal. The YUV matrix multiplier derives colors from RGB via the following formula:

Y = .299R + .587 G + .114 B
CR = R - Y
CB = B - Y

In this formula, Y represents luminance; red and blue are derived from it: CR denotes red and (V), CB denotes blue. V corresponds to CR; U corresponds to CB c. The U and V signals are carried on the same bandwidth. This system is sometimes referred to as Y/R-Y/B-Y.

Note: The name for this color encoding method is YUV, despite the fact that the order of the signals according to the formula is YVU.