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Written by: David "Spunk" Grampa - January 30, 2000
Last updated by: Dan "Tweak Monkey" Kennedy - December 13, 2002
If you think of any terms to add to this dictionary, please e-mail us!
Introduction - Tweak3D's 3D dictionary was created to define common audio and video terms that you might find on this web site and others of the type. Each definition is written in common English, some even having similes, metaphors, and simple analogies, in such a way that most people can understand what the terms mean (even the really confusing ones!). So don't hesitate thinking you won't even understand this all, read on!
A3D (Aureal3D) - An API optimized to create 3D positional sound and Doppler Effecting using only two speakers, unlike other forms of 3D sound applicable hardware/software that use four or more was the selling point of Aureal's A3D. Interestingly enough, it was made using algorithms initially developed by NASA. It is a program that allows you to hear sound in games, programs, etc, in 3D not only using a "which side is it coming from" (3D positional sound) technique, but also a "how far away is it technique" (Doppler Effecting). For example, when you are close to a sound in a 3D game, the pitch is higher, and when you are further away, the pitch is lower. In real life this is caused by the spreading out of sound waves over a certain distance. The only major difference to the nearly industry standard 3D sound is the Doppler Effect.
AC-3 - A technical term for Dolby Digital 5.1 Surround Sound, this is an algorithm that encodes sound into five separate channels and sends each to a different speaker. This is the technology that gives DVD movies realistic positional sound, and uses a digital input for a receiver (usually coaxial or optical). The concept is simple and requires many channels to create the effect that sounds are coming from all around. The standard left/right channels are in place, as is a center channel, subwoofer, and surround channels (five speakers, one subwoofer).
Accelerated Graphics Port (also AGP) - An expansion bus (a nice little slot on the motherboard which allows for expansion of a PC or customization of it when first being built) that was specifically developed by Intel for video cards, AGP is the current standard for video adapters. Most newly released high-performance video cards are available in only an AGP configuration, but some lower-end cards are available in PCI form. What is the difference between AGP and PCI? Sheer speed, AGP can send the CPU information at up to four times faster (266MHz, MHz stands for megahertz, just a term used to express how fast information is processed and sent in the computer world) than the former PCI standard expansion bus for video cards. Layman's terms: most video accelerators and video cards come in two different flavors, AGP and PCI. AGP is faster than PCI, giving an AGP board or video accelerator, a boost in terms of speed and performance over its PCI precedent. New PCs will certainly include AGP support, though early Pentium II and older motherboards did not have the luxury.
Accelerator - Any card or chip that is an extension of a computer is called an accelerator. Basically, it is a piece of hardware that processes specific information separately, freeing up how much information the CPU must process. Examples of information that can be processed separately include video, sound, and DVD decoding. Although most of the information processed by an accelerator must still take a visit to the CPU, substantial increase in speed, quality, and performance of specific information is present with an accelerator. The two most popular types of accelerators are video and sound accelerators, most oftenly referred to as a video card and sound card. Every modern PC today has a video accelerator, whether it be 2D, or 2D and 3D. Whether integrated or add-in, a video accelerator is a video accelerator.
Accuview - NVIDIA's anti-aliasing technology that claims improved performance and visual quality by using different sample positions. This mode also supports anisotropic filtering.
Algorithm - In short, an algorithm is a way of doing something. The term is used most often in Computer Science to explain how certain operations and programs should function. Algorithms may also include a pre-determined path in which variables are not present and don't need a definition. For example, the algorithm to find the hypotenuse of a right triangle is (a*a) + (b*b) = (c*c). So the square root of a squared plus b squared equals the length squared of the longest side of the triangle, the hypotenuse. By the way, that equation is the Pythagorean Theorem.
Algorithmic Procedure Texturing - A method of rendering imagery with virtually unlimited detail is called algorithmic procedure texturing. Simple enough, but for those that are already lost, it is an algebraic formula that allows an image or picture you see on screen to have an almost unlimited detail level. In fact, it is only limited to hardware capabilities.
Alpha-Blending - The ability to give an image, or pixel at the smallest level, a attribute that will determine whether the image will appear solid (opaque), invisible (transparent), or semi-transparent is known as alpha-blending. When used in conjunction with polygons, this method can be used to create glass, water,or anything else that is virtually 'see-through'. It is an effect that make games or other 3D environments appear to be more realistic.
Anisotrophic Filtering - An advanced form of texture filtering, anisotropic filtering has obvious benefits. Other texture filtering techniques can cause an object to become too smooth or blurred which is not ideal in most situations. Anisotrophic filtering blends a texture three dimensionally. Instead of just averaging a central pixel's color and those pixels around it (forming a square), anisotrophy averages a pixel and the pixels around it (forming the original shape), which is ideal for most polygons. All this improvement over trilinear filtering comes at a price though, and until recently most video adapters could not use anisotropic filtering without large performance hits.
Anti-aliasing - Now a standard with 3D acceleration, anti-aliasing smoothes the edges of diagonal lines across your screen that result from not high-enough of a resolution. For example, when you are looking down a hallway in Quake III, the floor and walls might look realistic, but the diagonal edge at the ceiling will appear jagged. Although filtering aids in elimination of some jagged edges, anti-aliasing is the most effective method of fixing such mistakes in a 3D environment. The most common types of anti-aliasing are super-sampling and multi-sampling.
API - Stands for Application Programming Interface, or just Application Interface. A standard piece of coding in an Operating System that programmers can link to and write forinstead of rewriting the entire bit of code. What does this have to do with 3D? A lot more than you would think. Imagine a game was written with its own unique code for displaying 3D. this would make the game virtually incompatible with most 3D accelerators because the code was not written to tell that specific 3D hardware what to do. 3D accelerators can be written to run with an API (that was written to run with a game, that was also written to run with that API). And also vice versa. In layman's terms, almost all games and 3D accelerators have a common language. The most popular 3D APIs are OpenGL and Direct3D. Just about any new 3D game imaginable is written with one of these APIs in mind, and almost every 3D accelerator supports these APIs. Glide was 3dfx's proprietary API, which for years was the standard for 3D gaming on the PC, since 3dfx Voodoo Graphics cards were the standard at the time for gaming enthusiasts.
API Extension - First see application programming interface, second an API extension is more of a personalized or 'added to' existing API making it more or less optimized for the specific hardware/software that it was written for. Two that come to mind are Creative Labs' EAX which works in conjunction with Microsoft's DirectSound3D, and 3dfx's optimized 3dfx OpenGL - an application extension of the plain old OpenGL API.
Aspect Ratio - The width to height ratio of a display area or image. This is found by taking an images height, and dividing it by its width and then simplifying the fraction. The common screen resolution of 800x600 simplifies down to an aspect ratio of 4:3, since 800/200 is 4, and 600/200 is 3.
Artifact - The results of poor texture compression technology are called artifacts. When you see a compressed texture where parts of it seem 'sponged' on, this is considered an artifact of the image. This is also apparent in 2D images with high compression, such as a JPEG image file that has been compressed to save disk space.
Auto Texture Compression - This is a graphics accelerator's ability to automatically compress a texture's file size, making graphics display faster without much loss in image quality. The result is less texture memory consumption, which can result in higher resolution textures with the same texture memory.