Microsoft DirectX 9.0

DirectX Glossary

alpha In computer graphics, the measure of a pixel's opacity. A pixel with the maximum alpha value is opaque, one with a value of zero is transparent, and one with an intermediate value is translucent.
alpha blend Method for combining two images that uses both pixel colors and alpha values to determine the color of the resulting pixel. This allows an image to be rendered on top of another image, with a blend of both images showing. When blending two pixels, the color components of both pixels are first scaled by their alpha values. Then, the bottom pixel is scaled by the inverse of the top pixel alpha value and added to the top pixel to form the final blended color.
alpha channel Opacity of an image defined by an alpha value per pixel, interleaved with the color components (for example, ARGB), an alpha value per pixel stored in a separate alpha surface, or a constant alpha value for the entire surface.
alpha color component Portion of a 32-bit color that determines its opacity. In this case, the alpha value per pixel is interleaved with the color components (for example, ARGB). Less commonly, this term refers to an image with an alpha value per pixel stored in a separate alpha surface.
alpha constant Level of opacity (alpha value) applied to an entire surface.
alpha edge blend Particular use of alpha blending (and alpha channel information) to reduce aliasing by blending edges, based on pixel coverage information.
ambient Description of a light source that illuminates everything in a scene, regardless of the orientation, position, and surface characteristics of the objects in the scene. Because it illuminates a scene with equal strength everywhere, the position and orientation of the frame that an ambient light source is attached to are inconsequential. Multiple ambient light sources are combined within a scene.
anisotropic filtering Mipmap filtering mode that compensates for anisotropic distortion.
anisotropy Distortion visible in the image of a 3-D object whose surface is oriented at an angle with respect to the viewing plane. The anisotropy is measured as the elongation (length divided by width) of a screen pixel that is inverse-mapped into texture space.
ARGB Alpha (opacity), red, green, and blue components of a pixel. Each color is represented in memory by data in BGRA order.
array object Group of objects organized into an array. Array objects make it simpler to apply operations to the entire group. The Component Object Model (COM) interfaces that enable you to work with array objects contain the GetElement and GetSize methods. These methods retrieve a pointer to an element in the array and the size of the array, respectively.
articulation A series of adjustments applied by a synthesizer to the pitch, volume, and other parameters of an instrument sound to make it more realistic.
ASP.NET HTML controls HTML elements exposed to the server so you can program them. HTML server controls expose an object model that maps very closely to the HTML elements that they render.
attach To connect multiple DirectDrawSurface objects into complex structures, such as those needed to support 3-D page flipping with z-buffers. Attachment is not bidirectional, and a surface cannot be attached to itself. Emulated surfaces (in system memory) cannot be attached to non-emulated surfaces. Unless one surface is a texture map, the two attached surfaces must be the same size.
attached Physically connected to the system. A device may be installed but not currently attached.
attack Period at the beginning of a force-feedback effect when the magnitude is reaching its basic or sustain level.
back buffer Nonvisible surface to which bitmaps and other images can be drawn while the front buffer displays the currently visible image.
back clipping plane Far boundary of a viewing frustum beyond which objects are not rendered. See also "front clipping plane."
bank select A MIDI controller that enables instruments to be chosen from different groups or banks, each identified by a 2-byte code.
billboard Primitive inserted into a 3-D scene that is oriented so that one face is toward the viewer. A texture, usually an animated sprite, is applied to the billboard to give the appearance of a 3-D object in the scene.
billboarding 2-D technique of simulating the appearance of a 3-D object in a scene. An application inserts a primitive, typically rectangular, into the scene, orients it so that one face is toward the viewer, and applies a texture or a set of textures. The texture or set of textures gives the appearance of an animated 3-D object.
bit block transfer (bitblt or blit) A graphics function that moves blocks of bits from one bitmap to another in the most efficient manner supported by the hardware.
bitblt Bit block transfer (bitblt). A graphics function that moves blocks of bits from one bitmap to another in the most efficient manner supported by the hardware.
blend factor Description of how each color component is blended in texture blending.
blend mode Algorithm used to determine how a texture is blended with the colors of the surface to which the texture is applied.
blending stage One step in a texture cascade. A blending stage includes one texture and a set of texture-blending operations that are used when blending multiple textures.
blit Bit block transfer. Sometimes called bitblt.
bob A technique for displaying interlaced video. In bob mode, each field is displayed individually. The gaps between scan lines are filled using interpolation.
bounds checking Process of checking that an on-screen image is displayed within the bounds of the screen.
bump mapping Technique for simulating the appearance of rough surfaces in 3-D scenes. Variations in depth are stored in a texture and applied to a primitive, using standard texture-blending techniques.
camera Direct3DRMFrame object used by the viewport to define the viewing position and direction. The viewport renders only what is visible along the positive z-axis of the camera frame, with the up direction in the direction of the positive y-axis.
camera space Frame of reference in which the viewer is at the origin, looking in the direction of the positive z-axis. Objects are transformed from world space to camera space by using the view transformation.
chordmap A scheme of chord progressions, arranged in a flowchart along a time line.
client/server session Microsoft?DirectPlay?session in which only the server stores the session's complete state, and each client has only a subset of the session's state. Each client receives only the information that is relevant to that computer from the server. When one computer changes something, it propagates the change to the server. The server then determines which clients it must inform of the change. See also "peer-to-peer session."
clip list Series of rectangles that describes the visible areas of the surface. The clip list cannot be set if a window handle is already associated with the DirectDrawClipper object.
clipper DirectDrawClipper object.
codec An abbreviation for compressor/decompressor. Software or hardware used to compress and decompress digital media.
collision detection Process for determining if any pixels for two images share the same location on the screen. See also "hit detection."
color key A color value used for pixel selection that enables transparent or translucent effects. When using a hardware blitter in graphics, for example, all the pixels of a rectangular area are blitted, except the value that was set as the color key. This creates nonrectangular sprites on a surface. In Microsoft DirectShow? an overlay surface is displayed in the region of the primary surface that contains the color key. In video production, color keys are used to combine two video signals. Also called a chroma key.
color space Model for representing color as three or more coordinates. Color-space models map color components onto a Cartesian coordinate system in three or more dimensions. A color space may use any of several types of color encoding and visualizing. The two most common types of color space models are RGB and YUV.
color table Array of n color values (normally RGB triples).
color-space conversion Technique for converting a color in one color space to another color space. Typically, this conversion is from YUV colors from a video source to RGB for display.
complex surface Collective term for several DirectDrawSurface objects, all of which are attached to a root surface. The complex-surface structure can be destroyed only by destroying the root.
composition A collection of tracks and (optionally) other compositions. At rendering time, the sources in a composition are composited into a single image.
control segment Musical segment that controls certain aspects of playback. Normally it is the primary segment, but a secondary segment can be designated as the control segment.
culling Removing a face from the list of faces to render. Faces can be culled using a number of techniques including: back face, view frustum, and occlusion culling.
curve In Microsoft DirectMusic? a continuous series of events with a start and end value, such as volume fade.
dark light Light source that removes illumination from a scene Dark light is created by specifying negative values for the colors of the light.
DCI Display Control Interface. Defined by the Intel and Microsoft corporations, DCI is an interface that offers improved graphics performance as a result of direct video memory access.
dead zone Area within the physical range of an axis where the axis is considered to be at the center.
deadband Zone around the offset of a force-feedback axis at which a condition is not active.
decal Texture that is rendered directly, as a visual. Decals are rendered into a viewport-aligned rectangle.
deinterlace To combine the interlaced fields in a video frame so that, during playback, the lines of the video frame are painted sequentially.
delta frame A video frame that contains only the changes from the previous frame. In contrast, a key frame contains all the data necessary to construct that frame.
destination color key Color that (in the case of blitting) is replaced or (in the case of overlays) is covered on the destination surface.
device window Visible application window that Microsoft DirectDraw?uses for display. Applications can have a device window for each display device attached to a given computer. See also "focus window."
DIB sequence In DirectShow Editing Services, a series of device-independent bitmap (DIB) files rendered in a sequence as video frames.
directional Description of a light source that is attached to a frame but appears to illuminate all objects with equal intensity, as if it were at an infinite distance from the objects. Directional light has orientation but no position, and it is commonly used to simulate distant light sources, such as the sun.
DirectPlay address Data format that DirectPlay uses to pass addressing information between lobby servers, applications, DirectPlay, and service providers. A DirectPlay address is a sequence of variable-length data chunks tagged with a globally unique identifier (GUID) that supplies all the address information needed by DirectPlay. Examples of address information are: the network address of a server, the network address of a player, the e-mail name of a player, and the network address of a session.
DirectX Media Object (DMO) A COM object that processes multimedia data streams from buffers allocated by the client.
dither Method to display a range of colors with a limited palette. Each pixel on the source image is represented by multiple pixels (usually a 2x2 square) on the destination image. From a distance, the eye blends the multiple pixels into one color that has more shades than the original palette. The technique results in a better visual appearance than the removal of low precision bits. See a standard graphics reference for details. Dithering is a supported option by DXSurface and Microsoft DirectX?Transform objects.
DLS Downloadable sounds. A standard for synthesizing wave sounds from digital samples stored in software. The DLS level 1 and level 2 standards are published by the MIDI Manufacturers Association.
DMO DirectX Media Object. A COM object that processes multimedia data streams from buffers allocated by the client.
downloadable sounds (DLS) A standard for synthesizing wave sounds from digital samples stored in software. The DLS level 1 and level 2 standards are published by the MIDI Manufacturers Association.
downsample To reduce the sampling rate of a signal.
downstream In a filter graph, the direction in which digital media samples travel.
emissive property Material property that determines whether a material emits light. The emissive property of a material is one of two properties that determines how the material reflects light. See also "specular property."
emissive setting See "emissive property."
enable frame Frame to which a light applies.
envelope In force feedback, a set of values that defines the shape of an effect by modifying the magnitude at the beginning (attack) and end (fade). In audio, a set of values that defines the shape of the amplitude or pitch of a sound. Downloadable sounds (DLS) level 1 defines a four-segment envelope: attack, decay, sustain, and release (ADSR). DLS level 2 defines six segments: delay, attack, hold, decay, sustain, and release (DAHDSR).
even field Second field, comprising a video frame in an odd/even field set. Also known as field 2.
execute buffer Fully self-contained, independent packet of information that describes a 3-D scene. An execute buffer contains a vertex list followed by an instruction stream. The instruction stream consists of operation codes, and the data that is operated on by those codes.
face Single polygon in a mesh.
fade Period between the central, or sustain, portion of a force-feedback effect and its end.
falloff Light attenuation between a spotlight's inner and outer cones.
field A portion of an interlaced video frame. With interlaced video, the scan lines of even-numbered fields fall spatially halfway between the scan lines of odd-numbered fields.
field polarity Quality determining whether a field is an even field or an odd field. In odd fields, the trailing edge of the vertical refresh (VREF) does not occur during a scan line. In even fields, the trailing edge of the VREF occurs during a scan line.
flimmering Shimmering appearance on 3-D primitives that results from a poor separation of z-values when doing decaling. Some pixels from the back texture are rendered onto the front texture and vice versa.
flip Process of swapping the addresses associated with the back and front buffer. This effectively swaps the image in the back buffer to the front buffer, thus displaying the image.
flipping chain Series of surfaces attached to each other that can be flipped. See also "flip."
flipping surface Any piece of memory that can be flipped. See also "flip."
focus window Application window, visible or not visible, that DirectDraw uses to hook window messages. The focus window's message handler receives input messages forwarded by DirectDraw. Applications can have only one focus window. See also "device window."
frame Invisible box that provides a frame of reference for objects in a scene. Objects can be placed in a scene by specifying their spatial relationship to a relevant reference frame. Visual objects take their positions and orientations from frames. In a movie or animation, a single image.
front buffer Rectangle of memory that is translated by the graphics adapter and displayed on the monitor or other output device.
front clipping plane Near boundary of a viewing frustum. Any object closer to the camera than the front clipping plane is not rendered. The height of the front clipping plane defines the field of view. See also "clipping plane."
gamma The curve in the function that maps changes in voltage to changes in brightness on a phosphor screen. The change in voltage needed to produce a specified change in brightness is not constant across voltage levels.
genlocking Process of synchronizing one video signal with another. Because they are synchronized, the genlocked signal can be mixed with the original signal, enabling dissolves, wipes, and other transition effects.
grid Subdivision of a beat. The number of grids per beat is part of the DirectMusic time signature.
groove level A value given to music during style playback. The groove level determines which patterns can be selected at any given time. The author assigns a range of groove levels to each pattern.
group In DirectPlay, a logical collection of players. DirectPlay supports groups within a session. By creating a group of players, an application can send a single message to the group, and all players in the group receive the message. A group is the means by which a network's multicast capabilities are exposed to the application. Groups can be used to organize players in a session. A player can belong to more than one group. DirectPlay provides methods for administering groups and their membership. In DirectShow, a top-level collection of compositions and tracks, all representing the same multimedia type. Each group produces a separate stream in the rendered project.
HAL The hardware abstraction layer (HAL) consists of hardware and device driver mechanisms that insulate applications from device-specific implementation details. If a capability requested by an application is not implemented by the current hardware, the capability is emulated by the software.
hardware blitter Hardware component, built into the display adapter, that performs efficient blit operations.
HEL Hardware emulation layer. The HEL provides software-based emulation of features that are not present in hardware.
HID Human Interface Device. A universal serial bus (USB) class representing devices that enable a human to control a computer.
hit detection See "collision detection."
host In DirectPlay, a virtual player whose identifier (ID) is DPID_SYSMSG. The host manages system messages and messages sent to all players in a session.
host byte order On an Intel x86 computer, the byte order for the system, or host, is little endian. Network byte order is always big endian.
HREF In a video stream, the horizontal refresh (HREF) is active to signal that the display is to begin a new scan line. See also "VREF."
HRTF Head-related transfer function. A mathematical representation of the effect of the listener's physiology on the pitch and timing of sounds arriving from different directions.
index palette DirectDrawPalette object whose entries are indexes into another palette object.
intelligent connect An algorithm used by the filter graph manager to build graphs and connect filters. If an output pin is specified, the filter graph manager renders the data from that pin by using default renderers. If two filters are specified, the filter graph manager attempts to connect them. It will insert intermediate filters if necessary.
interlace To display a video frame in two fields. One field contains the even lines of the frame, the other field contains the odd lines. During playback, the lines in one field are displayed first, then the lines in the second field are displayed.
interleaving The arrangement of video frames and audio samples in a file, such that video data alternates with audio data at regular intervals.
IPX service provider Service provider that uses Windows Sockets to communicate over a local area network (LAN) using the Internetwork Packet Exchange (IPX) protocol. The service provider supports only non-guaranteed messaging. A single computer can host only one DirectPlay session using IPX.
IRE scale International Radio Engineers scale. A scale of values ranging from 0 to 100 that defines the brightness level of a broadcast video signal. The spectrum of low-to-high IRE values describes increasing brightness levels of a video signal. At 7.5 IRE brightness, the black cut-off threshold for a National Television System Committee (NTSC) signal, the electron guns of an NTSC display device are cut off and do not display images.
kernel mode The operational state of a processor that enables full, unprotected access to a system. A driver or thread running in kernel mode has access to system memory and hardware.
key frame A video frame containing all the data needed to construct an image without reference to previous frames.
latency A delay in response. For example, in Microsoft DirectSound? it is the interval between the time at which a sound buffer plays and the time that the speakers actually reproduce the sound. In DirectPlay, it is the time that it takes for a packet to reach a specified destination. In DirectShow, it is the amount of time it takes a filter to process a sample.
LED Light-emitting diode.
letterbox A video display format in which black bars appear above and below the video image while it is played. The letterbox format maintains the original aspect ratio of an image when it is displayed in a window with a different aspect ratio.
light map Texture or group of textures that contain lighting information for a 3-D scene.
lobby client Lobby management routines associated with the user's computer, including launching applications, updating the user interface, and communicating with the lobby server.
lobby provider Client component (dynamic-link library) supplied by the developer of a lobby server. It implements communication functions with the lobby server, as requested by DirectPlay.
lobby server Lobby management routines associated with a remote server. The lobby server coordinates all the information about the users who are connected to a specific application.
lobby session Connection to a lobby server on which clients and the server have not been specifically written to interoperate.
lobby-aware application Application that, at a minimum, supports being launched from a lobby.
locked audio A video format in which the number of audio samples in a specified number of frames is fixed. In unlocked audio, the number of samples in a set of frames may vary, although the average equals the stated sample rate.
lookahead To use data from later in the stream to process the current data. For example, the next key frame is used to calculate a delta frame.
Mach bands Bands of color that are not smoothly blended across a 3-D primitive.
material Property that determines how a surface reflects light. A material has two components: an emissive property (whether it emits light) and a specular property, whose brightness is determined by a power setting.
medium Structure that identifies a hardware data path between two devices on the host system. They can be devices on the same card, such as a crossbar and a tuner on a TV card; devices on separate cards; or external devices. Kernel-mode filters based on the Windows Driver Model can use mediums instead of media types to determine pin connections.
mesh Set of faces, each of which is described by a simple polygon.
mipmap Also known as MIP map (Latin: multum in parvo, translated as "much in little"). A sequence of textures, each of which is a progressively lower-resolution, prefiltered representation of the same image. A higher-resolution image is used when a visible object is close to the viewer. As the object moves farther away (and gets smaller), lower-resolution images are used.
mix-in buffer In DirectSound, a buffer that receives data from other DirectSound buffers rather than directly from the synthesizer.
mixing In DirectSound, the process of combining sound buffers that are playing, and writing the result to the primary sound buffer, which supplies audio data to the sound hardware. There is no limit to the number of buffers that can be mixed, except the available processing time.
Mode X Hybrid display mode derived from the standard VGA Mode 13. This mode allows the use of up to 256 KB of display memory (rather than the 64 KB allowed by Mode 13) by using the VGA display adapter's EGA multiple video plane system.
model coordinates Coordinates that are relative to a local origin. See also "model space" and "world coordinates."
model space Frame of reference (used by model coordinates) that uses vertices relative to a single 3-D model's local origin.
motif In DirectMusic, a type of pattern played explicitly by an application to mark an event.
multipass texture blending Repeated rendering of a 3-D primitive while blending on a texture with each pass. This technique is widely used to achieve a variety of special effects.
multiplexer (MUX) A filter that combines multiple input streams into one output stream.
music value In DirectMusic, a note in a pattern within a style whose pitch is defined only when it is transposed to the current chord according to the current play mode and subchord level.
MUX Multiplexer.
nagling Algorithm that causes the Transmission Control Protocol/Internet Protocol (TCP/IP) service provider to buffer small data packets into larger ones before sending. Nagling prevents a TCP/IP protocol server from transmitting many very small packets by requiring the server to wait either until it has accumulated enough small data packets to combine them into a single large packet or until it has received an acknowledgment of the prior packet. Nagling can reduce message overhead (and decrease required bandwidth), but also causes a delay before small data packets are sent (increasing latency).
National Television Standards Committee (NTSC) The dominant television standard in the United States and Japan. NTSC delivers 30 interlaced frames per second at 525 lines of resolution.
nonregistered parameter number (NRPN) An identifier for a device-specific parameter that can be accessed through a MIDI controller. Nonregistered parameters can be used for different functions by different manufacturers.
normal vector Imaginary ray extending perpendicularly from a surface that defines the face's orientation.
NRPN Nonregistered parameter number.
NTSC National Television Standards Committee.
odd field First field comprising a video frame in an odd/even field set.
off-screen surface Conceptually rectangular area in memory that is generally used to store bitmaps to be blitted to a back buffer before being displayed. Commonly used to store sprites.
opcode Operation code that defines how to interpret the vertices in an execute buffer or how to change the state of the system.
overdraw Average number of times that a screen pixel is written to.
overlay surface Conceptually rectangular area in memory whose stored image information covers the image information of the primary surface to which it is applied. Overlays are assumed to be on top of all other screen components.
overlay z-order Determines the order in which overlays clip each other, enabling a hardware sprite system to be implemented under DirectDraw.
page flipping See "flip."
PAL Phase Alternate Line.
palette Set of colors used by an object or application. In DirectX, a DirectDrawPalette object.
palette index Integer index into the palette table array that is used to select a particular color.
palettized surface Collection of numbers where each number represents a pixel. Also called a color-indexed surface. Also, a DirectDrawSurface object that uses an attached palette to contain color information.
pan scan A digital video disc (DVD) display format in which a 16x9 video is cropped for display in a 4x3 window, by using parameters defined by the video author.
pan value Relative volume, measured in hundredths of decibels, between the left and right audio channels.
parallel point Description of a light source that illuminates objects with parallel light, but the orientation of the light is taken from the position of the parallel point light source. For example, two meshes on either side of a parallel point light source are lit on the side that faces the position of the source.
pattern In DirectMusic, a musical figure, one or more measures long, consisting of a basic sequence of music values for each instrument part.
PChannel Performance channel.
PCM Pulse code modulation.
peer-to-peer session DirectPlay session in which the session's complete state is replicated on all the computers in the session. The session description data (the list of players and groups and the names and remote data associated with each session) are duplicated on every computer. When one computer changes something, it is immediately propagated to all the other computers. This is the default mode of communication for DirectPlay. See also "client/server session."
performance In DirectMusic, an object that manages the flow of data from the source to the synthesizer, and controls global values, such as timing, tempo, and master volume.
performance channel (PChannel) A MIDI channel in a particular channel group on a particular port. In DirectMusic, a set of parameters used to play one or more parts in a segment. Each performance channel has its own instrument, pan, volume, and transposition settings, and belongs to a single audiopath.
perspective correction Technique of applying a texture map to a polygon that is angled away from the camera, interpolating so that the texture is stretched onto the polygon appropriately for the apparent depth of the polygon. Microsoft Direct3D?supplies perspective correction automatically.
phase alternate line (PAL) The dominant television standard in Europe and China. PAL delivers 25 interlaced frames per second at 625 lines of resolution.
pick To search for visuals in a scene, given a 2-D coordinate in a viewport.
PID Physical interface device. A universal serial bus (USB) class that enables humans to feel force feedback from a computer.
pitch Distance, in bytes, between an address that represents the beginning of a bitmap line and the beginning of the next line. Do not confuse memory pitch and memory width because not all display memory is laid out as one linear block. For example, with rectangular memory, the pitch of the display memory could include the width of the bitmap plus part of a cache. See also "width" and "stride."
player Single participant in a DirectPlay session. Each player is associated with a player ID that enables messages to be exchanged among players.
player ID Unique number that is assigned to each participant in a DirectPlay session when the participant is created. The application can exchange messages among players by using player IDs. The host is always assigned the DPID_SYSMSG player ID.
PNG Portable Network Graphics. A nonproprietary bitmap format using lossless compression.
point light Light source that radiates equally in all directions from its origin.
point list Simplest 3-D primitive. A collection of unconnected points in 3-D space.
power In the specular property of a material, value that determines the sharpness of specular highlights. A value of 5 gives a metallic appearance, and higher values give a more plastic appearance.
preroll To capture or play a number of video frames or a portion of audio data before encoding or rendering begins, in order to allow the source device to stabilize. Also used as a noun to describe the portion of the data to be prerolled.
primary buffer A sound buffer in which all data is mixed for the final time and then passed to the rendering device.
primary surface Memory containing the image being displayed on the screen.
projection space Frame of reference containing vertices after they are modified from their world space locations by the projection transformation. Projection space is a homogeneous cuboid space in which all vertices in a scene have x-coordinates and y-coordinates that range from -1.0 to 1.0, and a z-coordinate that ranges from 0.0 to 1.0. Projection space is sometimes referred to as post-perspective homogeneous space.
projection transformation Application of a matrix to vertices to change them from camera space to projection space.
pulse code modulation (PCM) A technique for digitizing audio into an uncompressed format by assigning a value to the amplitude of the signal at fixed intervals.
quality control Mechanism for adjusting the rate of data flow in response to run-time conditions.
quaternion Fourth element added to the [x, y, z] values that define a vector. Quaternions define a 3-D axis and a rotation around that axis.
reference clock A clock that provides a common reference time with which filters can be synchronized.
reference count Control for a COM object. When an object is created, its reference count is set to 1. Every time an interface is bound to the object, its reference count is incremented; when the interface connection is destroyed, the reference count is decremented. The object is destroyed when the reference count reaches 0. All interfaces to that object are then invalid.
reference time An absolute time established by a reference clock in the filter graph.
region In downloadable sounds (DLS), range of notes for which a particular digital sample is used in synthesizing an instrument's timbre.
registered parameter number (RPN) An identification number for a registered parameter that has been assigned a function by the MIDI Manufacturers Association and can be accessed through controllers.
RGBA Red, green, blue, and alpha (opacity) components of a pixel. Each color is represented in memory by data in ABGR order.
RHW Transformed vertices in homogeneous space. The (x,y,z) data has already been divided by w (multiplied by the reciprocal of w).
rolloff The attenuation of sound over distance.
root frame Frame in Direct3D that has no parent frame; it is at the top of a hierarchy of frames. The root frame contains the entire set of objects that make up a scene. See also "scene."
RPN Registered parameter number.
saturation In input and force feedback, adjustment to an axis range so that minimum or maximum values are retrieved or set before the physical extremities are reached. If the maximum value in a range is 1,000 and the maximum saturation point is set to 900, the maximum value is reached after 90 percent of the travel in that direction.
scene Entire set of objects that make up a virtual environment, including visible objects, sounds, lights, and frames. In Direct3D, the entire set of objects is contained in a root frame.
screen space Frame of reference that relates 2-D coordinates to locations in the frame buffer. Screen space coordinates typically display on a monitor. The origin, or (0,0) is defined at the upper left corner. Y increases in the downward direction; X increases to the right. You use a viewport transformation matrix to convert points from projection space to screen space.
script In DirectMusic, a file containing variables and routines that can be accessed from within an application.
secondary sound buffer Object that manages a single sound or audio stream and plays it to the primary sound buffer.
segment state An object created each time a segment is played. It is used to get information about the state of playback and the audiopath for that instance of the segment being played.
send A sound effect for a buffer that is applied by sending the sound data to a second buffer.
service provider Dynamic-link library used by DirectPlay to communicate over a network. The service provider contains all the network-specific code required to send and receive messages. Online services and network operators can supply service providers to use specialized hardware, protocols, communications media, and network resources.
session In DirectPlay, instance of several applications on remote computers communicating with each other. Before an application can start communicating with other computers, it must be part of a session. An application can enumerate all the existing sessions on a network and join one of them, or it can create a new session and wait for other computers to join it. Once the application is part of a session, it can create a player and exchange messages with all the other players in the session.
sink An object that manages the distribution of data from the synthesizer through buses to DirectSound buffers.
sink-in buffer A DirectSound buffer that receives data directly from the synthesizer rather than from other DirectSound buffers.
smart recompression In DirectShow Editing Services, the decompression and recompression of source data only when the data must be altered in some way before being written to the destination file.
sound buffer Object that manages DirectSound audio data.
source color key Color that (in the case of blitting) is not copied to or (in the case of overlays) not visible on the destination.
specular property Material property that determines how a point of light on a shiny object corresponds to the reflected light source. The specular property of a material is one of two properties that determines how a material reflects light. See also "emissive property."
spotlight Light source that emits a cone of light. Only objects within the cone are illuminated. The cone produces light of two degrees of intensity, with a central brightly lit section that acts as a point source, and a surrounding dimly lit section that merges with the surrounding deep shadow.
sRGB Color space defined by Microsoft.
static buffer A secondary sound buffer that contains an entire sound. Typically it is filled with data only once. See also "streaming buffer."
sticky focus In DirectSound, ability to play sound buffers when the owning application does not have the input focus. For example, a DirectSound application could continue to play a sound buffer while the user is working in another application.
stream time The current time minus the previous start time. Stream time is defined only in a running filter graph.
streaming buffer A secondary sound buffer that contains only part of a sound. Its data must be refreshed as it is playing. See also "static buffer."
stretching Blitting an image into a destination with different dimensions. This operation is supported directly by some hardware.
stride Synonymous with pitch. See also "width."
style In DirectMusic, a collection of musical patterns and other data that can be used to create a dynamic score. A style defines a basic melody and rhythm with variations, motifs, and embellishments, contains a time signature and a tempo, and can contain one or more bands.
subtype A GUID value that describes the specific format of data digital media stream.
surface Memory that represents visual images. This is often display memory but it can also be system memory. See also "complex surface," "off-screen surface," "overlay surface," and "primary surface."
sustain Period during which the basic magnitude of a force-feedback effect is attained, after the attack and before the fade.
swap chain A collection of one or more back buffers that can be serially presented to the front buffer.
synchronization point A media sample that can be decoded without requiring the decompressor to examine any other samples. One example is a key frame.
system message In DirectPlay, message from the player ID DPID_SYSMSG. All system messages begin with a DWORD value.
TCP/IP Transmission Control Protocol/Internet Protocol. A protocol developed by the Department of Defense for communications between computers. It is built into the UNIX system and has become the standard for data transmission over networks, including the Internet.
TCP/IP service provider Service provider that uses Microsoft Windows?Sockets to communicate over the Internet or LAN, using the TCP/IP protocol. The User Datagram Protocol (UDP) TCP/IP service provider uses DirectPlay packets for nonguaranteed and guaranteed messaging. Using TCP/IP protocol, a single computer can host multiple DirectPlay sessions.
tearing A visual artifact that occurs when one displayed video frame contains parts of two different source video frames. It is usually caused by improper synchronization between video rendering and the graphics display.
template In DirectMusic, a segment that can be used in combination with a chordmap to compose a new segment at run time.
tessellating Breaking an image into small square regions for processing or output.
texel Single element in a texture. When a texture has been applied to an object, the texels rarely correspond to pixels on the screen. Applications can use texture filtering to control how the system interpolates between texels to create pixels in a scene.
texture Rectangular array of pixels that is applied to a visual object in Direct3D.
texture blending Technique of combining the colors of a texture with the colors of the surface to which the texture is applied.
texture coordinates Coordinates that determine which texel in each texture is assigned to each vertex in an object.
texture filtering Process of mapping texel colors from one or more textures onto the pixels that comprise the image of a 3-D primitive.
texture mapping Application of a texture to an object. Because a texture is a flat image and the object is often not, the texture must be mapped to the surface of the object, using texture coordinates and wrapping flags. See also "texture coordinates" and "wrap."
texture stage Contains a texture and operations that can be performed on the texture. As used in DirectX, a texture stage takes two arguments and performs a blending operation on them.
thrashing Removing textures used in the current frame to reclaim texture memory for subsequent frames.
throttling Restricting the number of messages to avoid sending them faster than the underlying transport can deliver them.
time code A digital signal applied to a stream. The signal assigns a number to every frame of video, representing hours, minutes, seconds, and frames.
time stamp The time on a media sample indicating when it was recorded or when it should be scheduled for playback.
timeline In a DirectShow Editing Services video-editing project, the root node that contains all the other objects.
track In DirectShow, a collection of nonoverlapping sources with a common media type (audio or video).
transform filter A filter that receives data from an upstream filter, processes it, and then delivers it to the next filter in the graph.
trans-in-place filter A filter that can modify data without copying it to a new buffer.
transport A mechanism for moving data from one point to another. In a filter, the transport moves media samples across pins. In an external device such as a digital video (DV) camcorder, the transport channels data from the device to a computer, or from the computer to the device.
unit vector Vector with a magnitude (length) of 1.0.
Universal Serial Bus (USB) A serial bus with a bandwidth of 1.5 megabits per second (Mbps) for connecting peripherals to a PC.
upsample To increase the number of audio samples or pixels, through a process such as interpolation.
USB Universal Serial Bus.
VBI Vertical blanking interval.
velocity In music, the speed at which a MIDI key is pressed. This is roughly equivalent to the dynamic level at which the note is played in some instrumental timbres. In 3-D sound, for purposes of calculating Doppler shift, velocity is the speed at which a sound source or listener is considered to be moving.
vertex Point in 3-D space.
vertical blanking interval (VBI) In broadcast video, small period of time that elapses between video frames during which a display device refreshes its display for the next frame.
vertical refresh (VREF) In a video stream, the VREF is active to signal that the display is to begin a new screen. See also "HREF."
video frame Single image in a video stream, comprised of one odd field and one even field. See also "field."
view space See "camera space."
view state Accumulation of all a control's property values.
view transformation Application of a matrix to a model's vertices to change its orientation from world space to view space.
viewing frustum 3-D volume in a scene positioned relative to the viewport's camera. Objects within the frustum are visible. For perspective viewing, the viewing frustum is the volume of an imaginary pyramid that is between the front clipping plane and the back clipping plane. For orthographic viewing, the viewing frustum is cubic.
viewport Rectangle that defines how a 3-D scene is rendered into a 2-D window. A viewport also defines an area on a device into which objects are rendered.
virtual device driver (VxD) Software that manages a hardware or software system resource. These drivers are described using three letters, beginning with V and ending with D. The middle letter indicates the type of device, such as D for display, P for printer, T for timer, or x when the type of device is not under discussion.
virtual track In DirectShow Editing Services, any object that can be contained in a composition.
VREF Vertical refresh.
VxD Virtual device driver.
WAV A file format in which Windows stores sounds as waveforms. Such files have the extension .wav.
weave A method to display interlaced video. In weave mode, alternating fields are combined into a single image.
width Distance between two addresses in memory that represent the beginning of a line and the end of the line of a stored bitmap. This distance represents only the width of the bitmap in memory. It does not include any extra memory required to reach the beginning of the next line of the bitmap, such as a cache in rectangular memory.
world coordinates Coordinates that are relative to the origin of a scene. See also "model coordinates" and "world space."
world space Frame of reference used by world coordinates that declares vertices relative to a single origin within a 3-D scene.
world transformation Application of a matrix to a model's vertices to change its orientation from model space to world space.
wrap Procedure used to calculate texture coordinates for a face or mesh. The basic wrapping types are flat, cylindrical, spherical, and chrome.
z-buffer Buffer that stores a depth value for each pixel in a scene. Pixels with a small z-value overwrite pixels with a large z-value.
z-fighting See "flimmering."

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