eli5: What is Antisotropic Filtering and what does increasing or decreasing the stat do?

Question

Its a stat I’ve seen in all video games in the graphics section, along with another filtering one I can’t recall. What does it do?

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Answer 1

Okay, let’s start at the basics. Texture mapping is a way to distort a texture (a picture) so it fits onto 3 different shape. So for a wall in a game, we have a square distorted into a trapezium shape.

Now, if you go right down to the pixel level, we need to choose which pixel on the texture to map each screen pixel to. We do some calculations and find the middle of a pixel maps onto a certain point on the texture.

We call the pixels that make up a texture “texels”. We can pick the nearest texel. This was what the early graphics hardware did. It gives that coarse blocky look you see in 90s games.

An improvement is linear filtering. You pick the 4 nearest texels, and blend depending on distance. It looks a little better.

Ideally what we want to do is pick all the texels that map to a pixel.

We can approximate with “mipmapping”. Here we have lots of copies of the texture at different sizes (“Mip levels”). We choose the one with texels that best map to cover one pixel and do the linear filtering on that texture.

This actually looks pretty good. But textures are often at an angle. A pixel doesn’t map to a square. A rectangle is a much better approximation. So we choose a “Mip level” that’s a good size, and take several samples in a rectangular shape in the texture.

It looks a little nicer. It’s quite a bit slower though. Personally I think mipmapping gives the best performance/quality trade off. If you have the power, the slightly better image quality is nice.