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August 1998
A Glossary of Graphic Accelerator Board Terms
AGP: An extension of the PCI bus that overcomes the limitations of PCI for handling large amounts of 3D graphics data. Has a bandwidth of 133 MHz.
Alpha Blending: A visual effect that mixes two textures on the same object.
Anti-Aliasing: The process of smoothing graphics in order to achieve a higher quality image on-screen.
Bilinear Filtering: Averages the four nearest texels (textured pixels) to generate a higher picture quality. Used by some graphics accelerator manufacturers to make textures appear smoother and without blockiness.
Bus: Most commonly means the data pathway that connects a processor to memory or other peripheral buses, such as PCI and AGP that connect to the system.
Color Depth: The amount of colors displayable on your monitor.
Controller: A device that manages the flow of data between a computer and a peripheral. Specific devices like graphic accelerator board use their own kinds of controllers. Often referred to as a chip.
Device Driver: A program that lets peripheral devices communicate with computers. Graphic accelerator boards come with their own device drivers that can support extra features of the board.
Direct3D: Microsoftıs Direct3D is part of the larger DirectX standard. Direct3D is a type of API (Application Programming Interface) that sends 3D application instructions to the hardware that will display it. 3D developers write instructions to Direct3D, which then translates them to the graphics accelerator card. To take advantage of the API, both the application and the graphics card must support Direct3D.
Frame Buffer: The memory on a graphics card that stores rendered frames not being displayed on screen. They are then converted by the RAMDAC and displayed.
Fogging: Used to hide the background of a scene, usually a landscape, behind a layer of fog, requiring the mixing of the texturesı color values with a monochrome color, such as white.
Gouraud Shading: Giving the effect of shading to 3D objects by dividing surfaces into small triangles and applying different shades of color.
Lighting: Applying lighting to a scene to accentuate curves or create ambiance.
Memory bandwidth: Generally, bandwidth refers to data-carrying capacity and is expressed in Hertz (Hz) but itıs also common to use bits instead. In the case of RAM, bandwidth is a function of its rated speed and the size of its data path.
Mip Mapping: To improve the quality of mapped 3D textures, three copies or MIP levels of the same texture are made in different sizes to fit an object. There are three forms of MIP mapping, tile-base, per-pixel and tri-linear.
Palletized Textures: Using a method of palletized textures that assigns a Color Look-Up-Table (or CLUT) to each texture in a scene. More memory efficient than using the normal 16-bit color value.
PCI (Peripheral Component Interface): Most Pentium system use the self-configuring PC local bus called PCI. Designed by Intel, PCI has gained wide acceptance a few year ago beating out the older VESA local bus spec. It has a 33-66 MHz bandwidth - smaller than AGP.
RAMDAC (Random Access Memory Digital to Analogue Converter): Embedded in the controller that sits on a graphics accelerator board; translates the digital representation of a screen-full of information into an analog signal that the monitor can display. The faster the RAMDAC (measured in MHz), the higher the screen refresh rates that the card will support at a given resolution.
Refresh Rate: The measurement of times per second a monitor screen is repainted. This is measured in hertz (Hz). A slow refresh rate will cause the screen to flicker.
Rendering: The process of producing bitmapped images from a view of 3-D models in a 3-D scene. A camera is placed at a location, pointing in a given direction. Animation is a series of such renderings, each with the scene slightly changed.
Resolutio: The number of horizontal pixels times the number of vertical lines. This gives you the total number of pixels that can be displayed by your monitor.
SDRAM (Synchronous Dynamic Random Access Memory): Faster than standard DRAM. SDRAM incorporates new features that allow it to keep pace with bus speeds as high as 100 MHz.
SGRAM (Synchronous Graphics Random Access Memory): SGRAM contains the speed-enhancing features of SDRAM and adds graphics capabilities that enhance 3D graphics performance. Like SDRAM, SGRAM can work in sync with system bus speeds up to 100 MHz.
Texel: A texture element like its cousin the pixel, a texel is the base unit of a graphic. While pixels are the basic elements in any graphic, texels are their equivalent in a texture map.
Texture Mapping: Applying two-dimensional textures to 3D objects or scenes to make them appear more realistic. Perspective-correct texture mapping is the use of textures that are designed to fit with an object as a viewerıs perspective of the object changes.
Transparency: Lets the background show through selected parts of an image. The designer can designate one color in the imageıs palette as transparent. When the image is displayed, areas using that color reveal whatever is underneath.
Trilinear Filtering: Like its less sophisticated cousin, bilinear texture filtering, trilinear filtering is a complex technique used by 3D graphics cards to make movement through rendered landscapes realistic even in fast-moving games.
Z-Buffering: When two object are intersecting each other the z-buffer determines which portions of the intersecting objects are visible.
--Liz Levy
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