Anisotropic filtering is one of the more arcane terms you’ll encounter in a game’s settings menu. However, its impact isn’t hard to see: it reduces blurriness and visual artifacts in the distance. And compared to many other graphics settings, its impact on your FPS can be minor.
In this article, we’ll walk through the basics of what anisotropic filtering is, how it works, and how it differs from other forms of texture filtering.
How Does Anisotropic Texture Filtering Work?
Textures are two-dimensional images that fit over the surface of a three-dimensional object. They can add color, detail, and the impression of depth to a game when placed over in-game geometry (e.g. any in-game 3D objects that are viewable on-screen) or the user interface (e.g. a “heads-up display” of health bars, quick items, and so on).
Most game settings menus have a “Texture Quality” option that changes the resolution of the textures being used, with higher resolutions providing better-looking surfaces but using more of your graphics card’s VRAM.
Anisotropic filtering differs from the texture quality setting. Rather than switching out one texture for a higher-resolution version, it modifies the appearance of the texture to account for viewing angle.
As a general rule, enabling anisotropic filtering makes games look sharper with a relatively low performance cost.
But what does it actually do? Anisotropic filtering improves the appearance of textures viewed at oblique angles, rather than straight-on. That might sound abstract, but the onscreen impact can be dramatic.
Distant points on the surface of a cobblestone road, for example, can look blurry in-game without texture filtering. That’s because game engines use lower-quality substitutes for textures that take up small amounts of onscreen space, like cobblestones sitting a long way down the road. These rendering techniques cause artifacts and distortions of perspective that can be fixed with anisotropic filtering.
When filtering is turned on, the textures are modified to match the player’s viewing angle, creating a more defined vanishing point and a crisper appearance for objects farther from the “camera.” Unlike older filtering techniques, which treat textures as if they are perpendicular to the camera, anisotropic filtering modifies the textures to account for perspective.
This image demonstrates the visual improvements of anisotropic texture filtering:
The benefits of texture filtering are even more apparent when the player is in motion. Without filtering, obvious “bands” in quality appear on the ground as closer textures transition to farther textures. With filtering, textures appear smoother and the lines are more subtle.
What Anisotropic Filtering Setting Should You Use?
Configuring anisotropic filtering isn’t a simple on/off choice. Settings menus typically let you decide whether to set a value of x2, x4, x8, or x16.
These values change the sample rate. When set to x4, anisotropic filtering collects four samples per texel to decide the texture’s appearance. (A “texel,” or texture element, is the smallest unit within a texture map.) A value of x16, taking 16 samples, provides the greatest benefit to textures viewed at the steepest angles.
The improvement from 8x to 16x anisotropic filtering can be slight, as demonstrations like this Gamespot video show. Its visual impact can also vary greatly in different games. Though you may see diminishing returns with higher sample rates, it’s always worth testing x16 filtering to test whether you can detect the difference or notice an FPS drop.
How Does Anisotropic Filtering Differ from Bilinear and Trilinear Filtering?
Bilinear and trilinear filtering are older forms of texture filtering. Texture filtering helps map texels to onscreen pixels more accurately.
Bilinear filtering is a basic form of filtering that can smooth out a texture’s appearance and reduce blockiness.
Trilinear filtering improves on bilinear filtering by addressing the lines that appear in the distance as higher-quality textures are replaced by lower-quality substitutes.
Both bilinear and trilinear filtering are isotropic (or “uniform in orientation”) filtering techniques that assume texels are square within the rendered space. Anisotropic filtering allows different values on different axes, rather than uniform values. That means it allows for non-square applications of textures, such as in rectangular or trapezoidal shapes, with more lifelike results for textures viewed at steep angles.
Using bilinear or trilinear filtering can result in a blurrier image than anisotropic filtering. If your PC is struggling with x16 anisotropic filtering, it’s worth trying out lower values like x4 before falling back on the earlier forms of filtering.
How Do You Enable Anisotropic Filtering?
Most modern games allow anisotropic filtering out of the box. You can find it in the graphics settings menu under “Anisotropic Texture Filtering,” “Texture Filtering,” or “AF,” then set to a preferred value (like x8 or x16).
To improve the look of older games that don’t offer texture filtering in the settings menu, you can often apply texture filtering through your graphics card’s software. Try opening the 3D settings within the control panel of your graphics card software, then create a profile for the game you’re playing and enable anisotropic filtering within that.
When to Use Anisotropic Filtering
Anisotropic filtering can have a significant visual impact for a relatively small performance hit, especially compared to options like texture or shadow quality.
However, both the visual benefits of anisotropic filtering and its impact on FPS vary greatly with different games and different PCs. It’s always worth testing out different values, such as x4 or x8, to see what works best with your system.
Upgrading your GPU is a great way to unlock new levels of graphical fidelity in your favorite games. If you’re struggling to run anisotropic filtering at your preferred settings, consider upgrading to a system with an Intel® Arc™ GPU. Using Intel® Deep Link technology, Intel® GPUs and CPUs work together to boost gaming performance, battery life, and content creation. Read more here.