Anisotropic filtering is a technique used in the 3-D computing field to enhance the image quality of textures on rendered surfaces which are sloped relative to the viewer. This is achieved by eliminating aliasing, which is responsible for the jagged or pixilated quality of some graphics. In addition to its anti-aliasing qualities, this filtering also reduces blurring of sloped textures, an improvement over previous types of filtering known as bilinear and tri linear filtering. An important distinction of anisotropic filtering as compared to other anti-aliasing methods is that it affects only the textures on a shape, but not the shape itself.
Anisotropic filtering works by monitoring a given texture on a pixel-by-pixel basis, and mapping a pattern based on the projected shape of the texture at each pixel.
An anisotropic filtering technique includes defining pixel elements in two dimensions and defining at least one object having three dimensional surfaces in a three-dimensional model space and storing texel elements in two dimensions defining a texture map bearing a relationship to the three dimensional surfaces of the at least one object. Each pixel element to be texture mapped is divided into a group of sub-pixel elements and the sub-pixel elements are separately texture mapped. The resultant textures of the sub-pixel elements are averaged to obtain a texture for their respective pixel element.
In 3D computer graphics, anisotropic filtering (abbreviated AF) is a method of enhancing the image quality of textures on surfaces that are at oblique viewing angles with respect to the camera where the projection of the texture (not the polygon or other primitive on which it is rendered) appears to be non-orthogonal (thus the origin of the word: "an" for not, "iso" for same, and "tropic" from tropism, relating to direction; anisotropic filtering does not filter the same in every direction). Anisotropic filtering is relatively intensive (primarily memory bandwidth and to some degree computationally, though the standard space-time tradeoff rules apply) and only became a standard feature of consumer-level graphics cards in the late 1990s. Anisotropic filtering is now common in modern graphics hardware and is enabled either by users through driver settings or by graphics applications and video games through programming interfaces.
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