What Is Anisotropic Filtering - Graphics Explained

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Anisotropic filtering is a method in 3D computer graphics to improve the image quality of textures on computer graphics surfaces. With respect to the camera, the graphics are at an oblique viewing angle where the projection of the texture appears to be non-orthogonal. It eliminates the overlay effect, reduces blurriness, and preserves details at extreme viewing angles.

It is relatively intensive. In the late 1990s, it became a standard feature of consumer graphics cards. This is now common in modern graphics hardware. What Is Anisotropic Filtering, It can be enabled by video games through programming interfaces or by graphical applications, or by users via controller settings.

How Demanding Is Texture Filtering?

Settings vary in 2x, 4x, 8x, and 16x anisotropic filtering. These settings determine the maximum stability angle at which AF will filter the texture. 8x is twice as much as 4x, etc. The higher setting, the more VRAM will be used. Texture filtering is generally a much less demanding graphics solution, typically causing a 0 to 4% drop in frame rate depending on the settings used.

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Anisotropic Filtering

Trilinear filtering helps, but the ground still looks blurry. That is why we use anisotropic filtering, which greatly improves texture quality at steep angles.

To understand this, imagine a square window with a brick wall just behind it as our texture. The light shines through the window, creating a square shape on the wall. With bilinear and trilinear filtering, the texture is always sampled in the same way.

If the model is also directly in front of us, perpendicular to our view, that’s fine, but what if it’s tilted outwards? If we’re still testing a square, we’re doing it wrong and everything looks blurry. Now imagine the texture of a brick wall with your back to the window. This is the region where we should sample for this pixel, and as a rough analogy, anisotropic filtering is taken into account. Scale the MIP maps in one direction according to the angle at which we are viewing the 3D object.

This is a difficult concept to grasp, and I must admit that my analogy does little to explain the actual implementation.

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Screen Space Ambient Occlusion (SSAO)

SSAO efficiently estimates the environmental impacts of interception in real-time. It was developed by Vladimir Kaylin of Crytek and was first used in Crysis. The advantage of AO over traditional shading is that it takes into account the blocking of light and therefore creates shadows that give additional depth to the scene.

Basic SSAO is generally processed at half resolution and uses 16 occlusion samples per pixel. Unfortunately, rendering at low resolutions often causes unwanted flickering that is very difficult to hide in all situations. Therefore, SSAO +, an improvement over SSAO, boils down to the original solution. Therefore, more versions of SSAO were introduced.

The first was HBAO, which is processed at full resolution but uses only 4 samples per pixel, leading to much faster resolution. HBAO + improves with samples per pixel, enabling accurate shading twice as slow as HBAO.

Another technology, HDAO, is optimized specifically for GPUs but is used much less frequently in games than HBAO.

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AMD Catalyst Control Center

Open the AMD Catalyst Control Panel

Found in the Windows Control Panel.

Go to the Image Quality / Anisotropic Filtering tab.

Uncheck the “Use application settings” box.

Set the option to the desired sharpness level.

Apply the changes.

Nvidia Control Panel

Open the NVidia Control Panel

Found in the Windows Control Panel.

Go to the 3D Settings / Manage 3D Settings tab on the left sidebar.

Select the game in ‘Program to customize’.

Alternatively, manually select the executable using the ‘Add’ button.

Change the ‘Anisotropic Filtering’ option to the desired level of sharpness.

Apply the changes.

AMD Radeon software

Open the AMD Radeon software application.

Click Games.

Click Add, go to the game installation folder and select the game executable.

In the Radeon Software window, click the game icon.

Click Anisotropic Filtering Mode and select Override Application Settings.

For Anisotropic Filtering Level, select the quality.

Implementation of texture filtering in Unity

In Unity, Texture Filtering is set in the Project Quality settings.

To set the texture filtering settings for a texture to a unit:

  • Go to Edit.
  • Select Project Settings.
  • Select Quality to open the Project Quality Settings panel.
  • From this window choose the Anisotropic Texture drop-down menu.
  • Select the option by texture.

Then, for each texture, select it in the Properties section of the Project window to bring up the Texture Inspector window. When the window is open, set both the filter mode and the anisole level for that texture.

How to Optimize Anisotropic Filtering

Try the following optimization steps:

  • Start using a maximum anisotropy of two and then assess whether it provides sufficient quality. More samples can improve quality, but they also produce diminishing returns that are often not worth the cost of performance.
  • Consider using 2x bilinear AF instead of isotropic trilinear filtering. 2x bilinear is sharper and has better image quality in high anisotropy regions.
  • Use AF and trilinear filtering only for the objects that benefit most from it.

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Measures to Avoid Anisotropic Filtering

Arm recommends that you:

  • Do not use high levels of maximum anisotropy without reviewing the performance. 8x bilinear AF costs eight times more GPU computational power than a simple bilinear filter.
  • Do not use Trilinear AF without reviewing performance. 8x Trilinear AF costs 16 times more than a simple bilinear filter.

Anisotropic filtering on screen –

Anisotropic filtering can affect the frame rate. From the video card, it takes up video memory. However, the effect will vary from computer to computer. Without this filter, the texture is distorted when the in-game camera views the texture from an oblique angle.

Many ways

The fastest way is to take a point on an object and find the closest texel to that position. The resulting point then gets its color from that texel. This is sometimes called nearest neighbor filtering. This works quite well but can cause visual artifacts when objects are viewed from small, large, or awkward angles.

Anti-aliasing means thinking of pixels and texels as blocks in a grid that together form an image and using the area that a texel covers as a weight in a pixel. Since it is computationally expensive, many methods have been invented: MIP mapping, supersampling, anisotropic filtering.

Mip mapping stores multiple copies of the texture in a smaller resolution. Each MIP map has a quarter of the resolution of the previous MIP map. This speeds up texture mapping on small polygons.

In bilinear filtering, the four texels closest to the screen coordinate are sampled and the weighted average is used as the final color. In trilinear filtering, bilinear filtering is performed for the two closest MIP map levels and the results of both MIP maps are averaged. This removes the mipmap transition lines from the rendered image.

Both bilinear and trilinear filtering do not take into account the angle at which the texture is oriented towards the screen. This produces blurry results for textures that are angled back from the screen.

Anisotropic filtering takes up to 16 samples depending on the angle of the textured polygon. More texels are sampled at the recurring end than at the near end. It gives accurate results regardless of the orientation of the texture towards the screen.

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