What Is Anisotropic Filtering?

Anisotropic Filtering (Anisotropic Filtering) is used to filter and deal with the texture errors caused when the 3D object surface is tilted due to the change of viewing angle. The traditional bilinear and trilinear filtering techniques refer to "Isotropy" (isotropic), and the vector values in all directions are consistent, just like squares and cubes.

Anisotropic filtering

Anisotropic Filtering (Anisotropic Filtering) is used to filter and deal with the texture errors caused when the 3D object surface is tilted due to the change of viewing angle. The traditional bilinear and trilinear filtering techniques refer to "Isotropy" (isotropic), and the vector values in all directions are consistent, just like squares and cubes.

Chinese name

Anisotropic filtering

Foreign name

Anisotropic Filtering

Use

Filtering and processing when the perspective changes

Form

Bilinear and trilinear filtering technology

The principle of trilinear filtering is the same as that of bilinear filtering. It remembers the relative relationship between adjacent pixels and each other, and then draws it when the perspective changes. It is just that the acquisition range of trilinear filtering is larger, the calculation is more accurate, and the picture is more delicate.

Of course it takes up more resources. The filtering unit of Anisotropic Filt technology is not "boxy", its typical unit is rectangular, and it can also be transformed into trapezoid and parallelogram. A pixel on the screen can contain information of different texture units in one direction. This requires a "non-regular polygon" filter unit to ensure accurate perspective relationships and transparency. Otherwise, if there is a lot of information on the texture part on a certain axis, or if the image and texture in a certain direction have an inclination, then the final texture will become funny and the proportion will be out of proportion. The situation is even worse when the viewing angle is 90 degrees, or when processing the edge textures of objects.

Anisotropic filtering is the latest type of filtering method (relative to isotropic 2/3 linear filtering). It requires sampling 8 or more square pixels around the mapped points, and then maps the pixels to the pixels. For many 3D acceleration cards, anisotropic filtering with more than 8 pixel samples is almost impossible, because it requires more pixel fill rates than trilinear filtering. But for 3D games, anisotropic filtering is a very important feature, because it can make the picture more realistic, and it will naturally be slower than trilinear filtering.

Non-equivalence in Need for Speed 14

Results before processing:

Processed results:

After entering the advanced settings of the graphics card settings, you can see the adjustment of the anisotropic filtering in the sub-options of the 3D option. You can set from level 0 to level 16. The consumption of the graphics card will gradually increase. It will decrease accordingly. For low-to-mid-end graphics card users, there may be noticeable stuttering and dropped frames when playing games.

The figure below shows the comparison of before and after effects using anisotropic filtering in a classic 3D tunnel animation. It can be seen that when anisotropic filtering is not performed, the far side of the tunnel is relatively blurred; after adding anisotropic filtering, details such as plaster between the bricks are clearly visible ^[1] .

No effect of anisotropic filtering

Add the effect of anisotropic filtering