1x anisotropic filtering is basically no anisotropic filtering. So that's an option to disable it.
Topic on Talk:The Last of Us Part I
Sorry, it is still some form of AF, even if it is minor. So still sadly no way to FULLY disable it :( So, if we want to stick to the facts, then the note is currently correct.
No, it's not. The number there is by how much the sampler increase the number of texture fetches along an axis in case when the polygon isn't parallel to the screen - which is what AF does. 1X means that there is no increase and thus no AF.
https://developer.arm.com/documentation/102449/0100/Texture-filtering seems to suggest otherwise. As I'm not 100% sure, I'm asking this in the PCGW Discord :)
Asked it in the PCGW Discord's #articles channel and it indeed still applies AF: 1x (8 texels), 2x (16 texels), 4x (32 texels), 8x (64 texels) and 16x (128 texels). 1x thus does not equal Off and the game allowing only 1x as the lowest value with no option to turn it completely off thus warrant the "always on" value here. Regarding texels: "A “texel,” or texture element, is the smallest unit within a texture map." (https://www.intel.com/content/www/us/en/gaming/resources/what-is-anisotropic-filtering.html)
It's the same as off. AF 1x gives you the same filtering as just bilinear because it doesn't increase the sampling of blf/tlf - hence why it's "1x".
You can test it yourself instead of asking some Discord channels: https://nvworld.ru/utilities/aftest/ - here setting AF 1x is exactly the same as using linear filtering for minification.
As Mrtnptrs said, AF 1x does not equal Bilinear. Just because you can't see the difference between bilinear and 1x AF, it does not mean there's no difference.
What? If you can't see the difference then there is no difference. It's that simple. And AF 1x equals no AF (whether that means bilinear or something else depends on other texture filtering settings). Here's Unity docs stating this very clearly as an example: https://support.unity.com/hc/en-us/articles/210606003-How-does-the-Anisotropic-Textures-Quality-Setting-affect-each-texture-s-Aniso-Level- Here's another Unity related discussion which state this as clear as possible: https://forum.unity.com/threads/making-sense-of-anisotropic-settings.797085/ Don't make things up, please.
I think the sources you provided are Unity's internal-settings-specific and not talking about AF as a whole. But to make this fully clear, I took images of the exact same scene (right after loading a save game to have exact same character and camera position) of in-game 1x AF vs 0x AF forced through the control panel. I see a very very minor difference: the 1x-ingame seems to have a very minor difference/improvement regarding texture filtering compared to 0x-forced. Still, this difference is extremely minor, which is to be expected. Hopefully this answers your question.
Ok, I'll try one last time.
"A texture's maximum degree of anisotropy is specified independent from the texture's minification and magnification filter (as opposed to being supported as an entirely new filtering mode). Implementations are free to use the specified minification and magnification filter to select a particular anisotropic texture filtering scheme. For example, a NEAREST filter with a maximum degree of anisotropy of two could be treated as a 2-tap filter that accounts for the direction of anisotropy. Implementations are also permitted to ignore the minification or magnification filter and implement the highest quality of anisotropic filtering possible."
"...For example, a NEAREST filter with a maximum degree of anisotropy of two could be treated as a 2-tap filter that accounts for the direction of anisotropy..."
Which means that a degree of anisotropy 1 (1x) is equal to 1-tap filter - meaning that there is no supersampling happening and thus no anisotropic filtering.
https://registry.khronos.org/OpenGL/extensions/EXT/EXT_texture_filter_anisotropic.txt
"A maxAnisotropy value of 1.0 or lower disables anisotropic filtering."
https://developer.apple.com/documentation/scenekit/scnmaterialproperty/1395402-maxanisotropy
Now as to why you see differences between in-game 1x and CPL forced to no AF is a different matter. I'll take a look at the game a bit later.