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Inside Macintosh: Apple Game Sprockets Guide /


Glossary

3D See three-dimensional. See also spatial.

3D sound component See localization component.

3D sound source A part of the virtual audio environment provided by SoundSprocket that emits sounds. Defined by the SSpSourceReference data type. Compare listener.

Apple Game Sprockets A collection of system software components that provide capabilities (such as three-dimensional sound filtering or machine-to-machine communication) specifically intended to facilitate the development of games for Macintosh computers.

ambient Of a sound, to appear to be emanating from all directions. Compare binaural, localized.

angular attenuation The loss of a sound's volume due to a change in the angle between the sound source orientation and the vector between the source and the listener. Compare distance attenuation, reverberation attenuation, room reflectivity attenuation.

angular attenuation cone A cone that determines the direction of maximum sound intensity and the amount of attenuation that occurs as the angle between the orientation vector and the source-to-listener vector increases toward a predefined limit.

attenuation The loss of sound volume caused by some physical action on the sound (such as its traveling over a distance or reverberating off a wall). See also angular attenuation, distance attenuation, reverberation attenuation, room reflectivity attenuation.

axis element A continuous control element with or without a meaningful center--for example, a joystick or a gas pedal. See also button element, directional pad element.

back buffer The buffer DrawSprocket draws into while another image buffer is being displayed.

bilinear interpolation Bilinear interpolation averages the pixels and determines a pixel value that falls between the two original pixels.

binaural Of a sound, recorded with a localized effect. Compare ambient, localized.

blanking window A window with which DrawSprocket completely covers the display, hiding the desktop, menu bar, and other system resources, and providing a uniform background color for the game to draw over.

button element A two-state element. See also axis element, directional pad element, movement element.

camera placement structure A data structure that contains information about the placement (that is, the location, orientation, and direction) of a camera. Defined by the TQ3CameraPlacement data type.

Cartesian coordinate system A system of assigning planar positions to objects in terms of their distances from two mutually perpendicular lines (the x and y coordinate axes), or of assigning spatial positions to objects in terms of their distances from three mutually perpendicular lines (the x, y, and z coordinate axes). Compare polar coordinate system.

component A piece of code that provides a defined set of services to one or more clients. Applications, system extensions, and other components can use the services of a component. See also localization component, sound output device component.

context A combination of resolution and pixel depth associated with a particular display.

context attributes structure A data structure that DrawSprocket uses to pass and receive information about a context.

coordinate system Any system of assigning planar or spatial positions to objects. Compare Cartesian coordinate system, polar coordinate system.

dB See decibel.

decibel (dB) A unit of loudness, equal to 20 times the common logarithm of the ratio of the pressure produced by a sound wave to a pre-established reference pressure.

direct device A graphics device whose pixels directly specify the color with which they are to be drawn. Compare indexed device.

directional pad element A nine (sometimes five) state element. It has an idle position and eight (or four) states corresponding to directions. See also axis element, button element, movement element.

dirty rectangle An area of the back buffer that has been invalidated so that DrawSprocket knows it has been changed.

distance attenuation The loss of a sound's volume as it travels over the distance from the sound source to the listener. Compare angular attenuation, reverberation attenuation, room reflectivity attenuation.

Doppler effect The perceived change in the frequency of a sound caused by motion of the listener relative to the source of the sound.

Doppler shift The magnitude of the perceived change in the frequency of a sound due to the Doppler effect.

double buffering A way to emulate hardware page flipping in software. The game draws to a back buffer and then transfers the completed offscreen image to the hardware display.

DrawSprocket The component of Apple Game Sprockets that gives video games access to and control over display and device-access features.

echo See reverberation.

element A building block that corresponds to a device control and consists of a kind, a label, and a unique human readable identifier.

element event structure A data structure used to pass element event data during game play. Defined by the ISpElementEvent data type.

fault-tolerance That quality or capability of network system services that handles and recovers from unexpected network problems and failures transparently to the applications using the services, and that adapts well to the current conditions under which it is operating, shielding the applications as well as possible from these difficulties.

forward-pointing vector See orientation.

host The application that is sponsoring or controlling a game. A host application may also support a player in the same application.

gamma fade Alters the pixel intensity mapping to produce a fading effect. This type of fade is based on a gamma table, which accounts for nonlinearities in the display's color response.

group A set or logical collection of players currently participating in a game sharing a common element, such as team members or players with scores over 1000. A player may belong to more than one group.

human readable identifier A string that a game can display to identify an element for the user.

identity matrix Any n n square matrix with elements aij such that aij = 1 if i = j and aij = 0 otherwise. A point or vector that is transformed by the identity matrix remains unchanged.

indexed device A graphics device whose pixel colors are specified indirectly, through a color lookup table. Compare direct device.

InputSprocket A part of Apple Game Sprockets through which games can communicate with joysticks and other game-oriented input devices.

invalid-rectangle list A list of the rectangular areas in the back buffer that must be redrawn to the screen the next time the buffers are swapped.

kind A four-character sequence that identifies the type of data an element produces. Compare label.

label A four-character sequence that identifies the suggested use for an element. Compare kind.

listener (1) The part of the virtual audio environment provided by SoundSprocket that perceives sounds. Defined by the SSpListenerReference data type. (2) The user who is listening to the sounds produced using SoundSprocket.

listener unit The unit of measurement associated with a particular listener. By default, the listener unit is the meter, but you can change the listener unit by calling the SSpListener_SetMetersPerUnit function.

localization component A sound component that provides 3D filtering for the sounds passed to it.

localized Of a sound, to appear to be emanating from a specific location in space. Compare ambient, binaural.

medium See sound medium.

message A complete set of information transmitted among players in a game. Messages may be broken into packets by NetSprocket for actual transmission over the network.

monophonic sound Sound consisting of a single channel. Compare stereo sound.

multichannel sound See stereo sound.

need structure A data structure that describes the requirements the game has for input. Defined by the ISpNeed data type.

NetSprocket A part of Apple Game Sprockets that provides streamlined, high-performance networking capabilities for multi-user games.

normal (a.) Perpendicular. (n.) A normalized vector.

normalized vector A vector whose length is 1.

opaque For a data structure, not publicly defined. You must use functions to get and set values in an opaque data structure.

orientation A vector that indicates the direction of a listener or a sound source. For a listener, the orientation is the unit vector beginning at the midpoint of the line connecting the two ears and pointing straight out through the listener's nose. Compare up vector.

origin In Cartesian coordinates, the point (0, 0) or (0, 0, 0). The coordinate axes intersect at the origin.

overlay An image that appears over the back buffer and is automatically applied just before the back buffer is swapped.

page flipping Drawing done to an offscreen video page located in VRAM that can be displayed by the video controller in rotation with other VRAM pages.

pixel depth Number of bits per pixel.

player A logical entity associated with each person who is participating in a networked game session.

play state The state of a context; it can be one of active, paused, or inactive.

polar coordinate system A system of assigning planar positions to objects in terms of their distances (r) from a point (the polar origin, or pole) along a ray that forms a given angle (q) with a coordinate line (the polar axis). The polar origin has the polar coordinates (0, q), for any angle q. Compare Cartesian coordinate system.

polar origin The point in a plane from which the polar axis radiates. Also called the pole.

pole See polar origin.

polyphonic sound See stereo sound.

position (1) Of a listener, the midpoint of the line connecting the two ears. (2) Of a sound source, the center of the bounding box.

private See opaque.

QuickDraw3D A graphics library developed by Apple Computer, Inc., that you can use to create, configure, render, and interact with models of three-dimensional objects. You can also use QuickDraw3D to read and write three-dimensional data.

reference distance The distance, in meters or listener units, from a listener to the point at which a sound was recorded.

resolution The horizontal and vertical timing of a display mode.

reverb See reverberation.

reverberation The bouncing of a sound off walls or other objects.

reverberation attenuation The amount of reverberant signal, in decibels (dB), to mix into the output sound. Compare angular attenuation, distance attenuation, room reflectivity attenuation.

room reflectivity attenuation The loss of a sound's volume as it bounces off walls. Compare angular attenuation, distance attenuation, reverberation attenuation.

room size The distance, in listener units, between two reverberant walls spaced equidistant from the listener. A room size of 0.0 indicates that no reverberation is to occur.

rotate To reposition an object by revolving (or turning) each point of the object by the same angle around a point or axis.

sound Anything perceived by the ear.

sound channel A path that sound data traverses from an application to the sound output device. A sound channel is associated with a queue of sound commands and with other information about the audio characteristics of the sound data. See also sound channel record.

sound channel information selector A value of type OSType that determines the kind of information to get or set for a sound channel.

sound channel record A structure that represents a sound channel. Defined by the SndChannel data type.

sound component A component that works with the Sound Manager to manipulate audio data or to communicate with a sound output device. See also localization component, sound output device component.

sound component chain A chain of sound components that links a sound source to a sound output device.

sound component link structure A structure that represents a link in the sound component chain of a sound channel. Defined by the SoundComponentLink data type.

Sound Manager The part of the Macintosh system software that manages the production and manipulation of sounds on Macintosh computers.

sound medium A substance through which sound can travel.

sound output device Any hardware device (such as a speaker or sound synthesizer) that produces sound.

sound output device component A sound component that communicates with a sound output device.

SoundSprocket A part of the Apple Game Sprockets that provides three-dimensional sound filtering and other sonic capabilities for Macintosh computers.

sound source See 3D sound source. (Do not confuse with sound sources as defined by the Sound Manager.)

source See 3D sound source.

source mode A feature of a listener that determines the type of filtering that is applied to a source sound.

spatial Contained completely in three dimensions (for example, a box).

standard temperature and pressure (STP) A temperature of 20 C and a barometric pressure of 760 mm.

stereo sound Sound that simultaneously consists of two or more channels. Also called polyphonic sound or multichannel sound. Compare monophonic sound.

STP See standard temperature and pressure.

three-dimensional Appearing to exist in three dimensions.

transformation matrix A matrix that defines the transformation to be applied to a listener or a sound source.

transform matrix See transformation matrix.

transparency mask The transparent areas of an overlay that allow the back buffer to show through.

movement element An element that produces data given both as x-y data and as directional data, allowing the game to use whichever data is suitable. See also axis element, button element, directional pad element.

triple buffering Adding a extra buffer to the back buffer queue so that the game can continue drawing into the extra buffer while the first back buffer is being drawn to the display.

underlay An image that is used as a background for your back buffer and is automatically applied just before the back buffer is drawn into.

unit cube A box whose three defining edges have a length of 1.

unit vector See normalized vector.

up vector A vector that indicates which direction is up. Compare orientation.

vector A pair of or three of floating-point numbers that obeys the laws of vector arithmetic. Compare normal.

virtual audio environment The combination of a single listener and one or more 3D sound sources.

virtual source A reflection of a real sound source. Defined by the SSpVirtualSourceData data type.


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© Apple Computer, Inc.
2 JUL 1996




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