Graphic effects: What Is Anisotropic Filtering?Posted on March 22nd, 2009 No comments
Anisotropic filtering (AF) is a graphic algorithm of improving the surface texture of an object. Where anti-aliasing is a method of making the edges of an object smoother, the anisotropic filtering is a method of enhancing the way how the objects looks inside, it concerns to all spaces between the edges. Every 3D objects that are used to build a game environment are textured. Texture is no more than a “coat of paint” that covers all those flat polygons to make them look like skin, wood, metal or bricks in the wall. Anisotropic filtering is a technology that became an standard effect in graphics cards in the early 90’s. Now the anisotropic filtering is widely used in graphics hardware.
Types of anisotropic filtering(AF)
There are three types of anisotropic filtering (AF). We can differentiate three methods of AF - bi-linear, tri-linear and full anisotropic. The anisotropic filtering is very powerful method, but it also uses lots of GPU performance. Settings that are available for anisotropic filtering are from 2x to 16x. When the level of anisotropic filtering is higher it provides more clear and sharp texture details, but it effects with more GPU usage. Modern nVidia graphic card such as Geforce 285 or even older models like Geforce 8800 handles 16x anizotropic filtering in resolution 1280 x 900 with no problem. For Geforce 285 even 1680 x 1050 is not a challenge, that because of use higher-quality AF algorithm. You can feel the difference between Anizotropic Filtering ON and OFF. Just take a look how anizotropic filtering looks like in action. These examples are a screenshots from 3DMark06 - the graphic benchmark tool. You can open those examples in a new window or tab, switching between them you can see the true difference.
3DMark06 Anisotropic Filtering (AF) OFF:
3DMark06 Anisotropic Filtering (AF) ON:
In short, anisotropic filtering is used when the generated textures are away from the viewer. It gives a smoother border between High resolution textures close to the viewer and lower resolution textures which are used away from “your eyes”. It is very useful for the textures in games with the far horizon. Of Course the textures resolution decreases looking further.
Anisotropic filtering vs. graphic cards performance
Anisotropic filtering can have an effect on games performance, even more when it’s used together with Anti Aliasing (AA). Companies building graphic cards such as nVidia are developing this filtering method to gain the best performance. To speed up AF, Nvidia specialists have initiated a special algorithms that makes Anizotropic Filtering calculations faster. Unfortunately it effects the lower amount of AF varies depending on the angle of the surface. The newest cards from nVidia use a higher-quality AF algorithm that have no problem with it but it results in a more round pattern.