Glossary

2D	Two-dimensional graphics, expressed in either real-world units (miles, meters, etc.) or in device coordinates x and y.
3D	Three-dimensional graphics expressed in either real-world units (miles, meters, etc.) or in device coordinates x, y, and z.
AGP	Accelerated Graphics Port. A dedicated slot for graphics, AGP provides wider bandwidth for data transmission and communicates directly with main memory.
Alpha Blending	Additional information for each pixel for creating transparent materials.
Anti-Aliasing	Anti-aliasing is used to make jagged edges appear smooth. The most common technique is to make a smoother transition from the color of the line, or edge, to the color of the background. This will result in edge blurring to some extent.
API	An Applications Programmer's Interface (API) is a specification which provides a standard set of functions which software vendors must support for their products in order to take advantage of 3D hardware acceleration. Because it is not a given that every system will have a 3D hardware accelerator installed inside, the 3D APIs must also provide a software only solution for 3D in the form of a software 3D driver.
Applications	A computer program written for a specific purpose, such as word processing or page layout.
Back Buffer	Image region formed in the background of the frame buffer during double buffering.
Back Face Culling	Method used to calculate the hidden faces of a 3D object.
Bi-linear Filtering	Low end game consoles (and competing PC graphics chips) tend to use nearest neighbor sampling to map texture-map pixels (or texels) to image pixels. This results in various forms of aliasing, as small movements cause full pixel changes in the image. Bi-linear filtering greatly reduces this phenomenon, by using a weighted average of the four nearest texels in computing the image pixel. The resulting quality difference is dramatic.
Binary	Having two states. In computers, binary is 0/1 (zero and one). Used to code data for computation.
Buffer	A temporary storage area, often used to compensate for speed differences between system components. Often, additional memory is reserved for temporarily holding data that’s being transferred between a CPU and a peripheral (such as disk, printer, or image display). Buffers are specially useful to compensate for differences in data-flow rates, for providing a place for data to reside when events are asynchronous (for example, data being written to a display controller might have to wait while the graphics processor completes its current operation), and to hold data still (as in a video frame buffer). Some buffer memory is part of the addressable memory of the CPU; some buffer memory is part of the peripheral.
Bus	A communication line consisting of a parallel data path within the computer system that’s shared by system components. Usually described by the width of the parallel lines available, typical computer buses are 8-, 16-, or 32-bits wide.
CAD	Computer aided design, or computer aided drafting.
CPU	Central processing unit. The primary processor in a computer.
Chip	An integrated circuit.
Color	The individual components of white light as perceived by the human eye. Color monitors use the three basic components of color to which the human eye responds: red, green, and blue. The final color seen on the screen is created by mixing these primary colors.
Computer Graphics	The overall discipline of creating or manipulating graphic images and pictorial data with computers. These can be used for CAD, animation, design, architecture, scientific imaging, business graphics, etc. Computer graphics systems are usually interactive, displaying images on a computer screen as they’re being created or manipulated.
DCC	Digital Content Creation (DCC). The production of professional visualizations for the digital media sector and entertainment industry.
DRAM	Abbreviation of Dynamic Random Access Memory. Non-permanent memory for read and write operations.
Double Buffering	Imagine the old animation trick of drawing a cartoon character on the corner of a page of paper, and altering the drawing slightly on following pages of paper. When the sheaf of paper is complete and the pages flipped rapidly, the cartoon character gives the illusion of smooth motion. Double buffered 3-D animation on the PC works in much the same way, with the next position of the character fully drawn before the page is flipped. Viewing 3-D animations without double buffering would be like looking at the animated cartoon if the character were being redrawn with every flip of the page, the animation would appear to "flicker". Double buffering requires having two areas reserved on the frame buffer of the 3-D graphics card; both regions need to be the size of the visible screen and one buffer.
EDO-RAM	Extended Data Output Random Access Memory (Hyper Page Mode). Very common in graphics boards, as the most recent data persists in memory. Allows for a speed advantage.
Flipping	The image generated in the back buffer is displayed.
Frame Buffer	A dedicated memory area in a computer or in a separate dedicated board, for temporary storage of pixel data to be displayed in one frame on a monitor. The depth of the frame buffer is determined by the number of bits stored for each pixel, which determines the dynamic range or number of colors and intensities that can be displayed.
Front Buffer	Visible image page in double buffering.
Fogging	Fogging uses blending to mix a computer pixel color with a fog color dependent on some depth related function.
Gouraud Shading	Gouraud shading (or smooth shading), is an algorithm which draws smooth shadows across the face of an object. The effect of this algorithm is to cause the viewer's eyes to extrapolate depth information and curvature information from the surface of the object. Gouraud shading works by reading the color information at the three coordinates of a triangle and interpolating the intensities in red, green and blue smoothly between the three coordinates. Gouraud shading is the most popular algorithm used to draw 3D objects on a 2D screen today. Most objects can be represented in 3D, by using the Gouraud shading algorithm, with amazing realism.
HiColor (High Color)	15 bpp or 16 bpp (bits per pixel) graphics color mode. (32,768 or 65,536 colors)
Interactive	Interactivity describes the behavior of an application program which a user can act on the output of the application to immediately add to, change, or remove that output.
MIP Mapping	MIP mapping uses some clever methods to pack texture image data into memory. To use mip mapping, you provide all sizes of a texture in powers of 2 between the largest size and a 1 x 1 map. The smaller maps are typically filtered and averaged-down versions of the largest map.
OpenGL	3D software interface (3D API). Implemented in Windows NT and available for Windows 95. Based on Iris GL from Silicon Graphics and licensed from Microsoft.
PCI bus	Abbreviation for Peripheral Component Interconnect bus. An advanced bus system, i.e. a system of parallel data lines to transfer information between individual system components, especially to expansion boards.
Perspective Corrected	Games today tend to use relatively large triangles, and employ texture maps to give the appearance of much more detail than would otherwise be possible. While maintaining correct perspective in the texture mapping process is compute-intensive, the alternative approaches result in visible distortion and swimming textures, which are distracting in mild doses and nauseating in larger ones.
Pixel	A combined term for picture element, the smallest unit of a video display. Also known as a pel. Pictures on the screen are made up of hundreds of thousands of pixels, combined to form images. A pixel is the smallest segment of a raster line that can be discretely controlled by the display system, and also the coordinate used for defining the horizontal spatial location of pixel within an image. Pixels on a monitor are the illuminated dots of glowing phosphor, the smallest element of a digital image. A pixel size can be no smaller than the spot a monitor can create. In a color monitor, spots consist of a group of triads. Triads are composed of three different phosphors: red, green, and blue. The phosphors are laid along side each other. Pixels can vary in size and shape depending on the monitor and graphics mode. The number of dots on the screen are measured in width-by-height fashion.
Pixel Clock	The pixel clock or pixel frequency indicates the number of pixels drawn per second in MHz (million pixels per second).
RAM	Abbreviation for Random Access Memory. Chip memory of a computer or expansion board that can be read from and written to (unlike ROM = Read Only Memory.)
RAMDAC	The RAMDAC converts digital signals to analog signals on a graphics board. VGA monitors are only capable of processing analog signals.
Real-Time	A recording, or playing speed that shows things as they occur, between 24-30 frames per second.
Rendering	Process of calculating the representation of as 3D scene in which the position and color of each point in space is determined. The depth information is held in the Z buffer. The color and size information is held in the frame buffer.
RGB	An additive color system in which the resultant color is a function of the intensity of each primary (red, green, and blue). The best known device that uses the RGB system is the color monitor.
Resolution	The number of pixels, represented by bits in the display memory, also known as addressable resolution. A display memory can be organized by pixels (bits) in the x axis (pixels per line) by the number of pixels in the y axis (lines) and by the number of memory planes in depth. A standard VGA display memory is 640 pixels across by 480 pixels (or lines) down, and typically 8 bits deep. The higher the resolution, the greater the detail and the more information that can be stored. Not all stored information can be displayed.
Shading	or rendering is a way to define the colors on curved surfaces in order to give an object a natural appearance. To achieve this, the surfaces are subdivided into many small triangles. The three most important 3D shading methods differ in the algorithm used to apply colors to these triangles. Flat Shading. The triangles are uniformly colored. Gouraud Shading. The color shades on a triangle are calculated by interpolating the vertex colors, resulting in a smooth appearance of the surface. Phong Shading. The color shades on a triangle are calculated by interpolating the normal vector.
Single Buffer	In contrast to double buffering, the single mode draws the new image in the visible portion of the video memory, causing interactive 3D displays to flicker.
Texture Mapping	The process of wrapping an image (bitmap) around an object. (e.g. a wallpaper/video on a wall). Even a video can be used as a texture map.
Transparency	In computer graphics, color is very often described in terms of RGB values, or red, green, and blue values. In 16-bit color, for example, there are 16 bits of data to describe color, with 5 bits allocated to red, 6 bits to green and 5 bits to blue. Alpha is an additional color component that is used to blend colors. Alpha can also be thought of as a transparency value, it defines whether a color can be seen through or not. The most important use of alpha in 3D graphics is to create irregular shaped objects with very few polygons.
Tri-linear Filtering	Textured objects can be viewed, like any other objects in a scene, at different distances form the viewpoint. In a dynamic scene, for example, as a textured object moves farther from the viewpoint, the texture map must decrease in size along with the size of the projected image. To accomplish this, the graphics engine filters the texture map down to an appropriate size for mapping onto the object, without introducing visually disturbing artifacts. To avoid such artifacts, most graphics programs allow the specifying of a series of pre-filtered texture maps of decreasing resolutions, called mip maps. Then, the graphics program a utomatically determines which texture map to use based on the detail in the texture map of the image that’s drawn on the screen—as the image of the object gets smaller, the size of the texture map decreases.
TrueColor	Graphics mode with 16.7 million colors (24 or 32 bits per pixel). In this mode, the color information saved in the display memory is not translated by a look-up table, but passed directly to the D/A converter. This means that the full color information must be saved for each pixel.
VESA	Video Electronicx Standards Association. A consortium for the standardization of computer graphics.
VRAM	Abbreviation of Video Random Access Memory. Memory chip for fast graphics boards.
Z-buffering	Just as the frame buffer contains all of the color information for every pixel on the screen, the z-buffer, or depth buffer, contains all of the depth information associated with all of the pixels on the screen. And just as more bits per pixel for color in the frame buffer corresponds to more colors available on the desktop, the bits per pixel in the z-buffer correspond to more units of depth available in the scene. Typically a z-buffer is at least 16-bits per pixel deep. 3D hardware accelerators need to have a local z-buffer on the graphics card to avoid heavy two-way traffic over the system bus. The z-buffer can be implemented in either DRAM or VRAM.