Anisotropic filtering

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Anisotropic filtering (from the Greek: aniso not equal, tropos direction) is a method used in graphics processing in, for example, 3D games, in order to maintain the impression of sharpness in distant textures . This blurring occurs above all at flat viewing angles, while almost orthogonal viewing directions can be treated sufficiently well with other methods (e.g. mipmapping ).

The difference between trill-linear filtering and anisotropic filtering becomes particularly well visible at an acute viewing angle.

Among other things, there is:

The advantage of the anisotropic is that, depending on the object and viewing angle, it processes the textures and thus filters them "inconsistently".

Another advantage is that the anisotropic filter makes the transitions between the different texture levels smoother and thus their change is not so noticeable.

However, the method requires a large memory bandwidth and can therefore slow down the application significantly.

There are several implementations of anisotropic filters:

  • Footprint Assembly - often as anisotropic filtering referred
  • Integral image , summed area tables (only suitable for texture improvement at full 90 ° angle)
  • RIP mapping (no real anisotropic filtering)
An example of an anisotropic mipmap: the actual image at the top left is surrounded by filtered, linearly transformed copies of lower resolution. In contrast to the normal mipmap , the aspect ratios are not retained.

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