anti aliasing vs. anistrophic filtering

[Godshatter]

ok, i know what anti-aliasing is (ive been using software like bryce 5 for years) but what exactly is anistrophic filtering?

also, what kind of changed will i NOTICE by lowering/increasing aa or af to increase my fps (i have a radeon 9800xt 256mb)

say 2x AA and 4AF versus 4x AA and 8AF (or other combinations). differences OTHER than increase'decrease in frame rate

[AndrewB]

Anisotropic filtering makes textures look sharper in the distance. Sometimes you notice that the ground gets blurry when it's farther away. AF helps undo that.

[Shadowfox]

I'm not positive, but I believe enabling Anisotrophic Filtering results in sharper textures.

[Mogul]

What a coincidence, that a thread can go hours with hardly being looked at, and then two people reply almost simultaneously. Heh.

[SyntherAugustus]

AntiAliasing "melts" the models into the game so it seems more realistic. It also allows you to see sharper textures further away. AnistroFiltering just makes textures not look so edgy.

I would boot up a game but I'm a bit lazy atm.

[AndrewB]

Yeah, the last thing you want during a bad mood is edgy textures nagging you.

[Sephiroth]

AA smoths edges out, like on modles, maps(structures and such), text and just about anything else that would need it. you can "force" it to be used but it can make some things in some games a bit wierd, like mess up the text.
i remember reading how it worked but forget most of it. i just know it can makes things look better.

AF sharpens up the textures. i think this is a bit newer than AA. Not to sure about how it works. I am not a programer so i dont worry about it. All i know is my games look good

[Bucket]

If it's what I think it is, 2AA and such raises the rendered area by a certain percentage. Starting with a specific example:

Say you have a blue 3D box floating in a yellow space. If you put your face really close to a rendered image of this WITHOUT anti-aliasing, the box will look like it's been drawn in MSPaint(as in, pixels will either be blue or yellow, with no blending). If the box was angled as to cross through a specific pixel, it wouldn't matter. The video card decides which color is more prominent within the space and displays only that color-- so it's either blue or yellow, and the line you're seeing looks jagged.

Anti-aliasing actually brings blending into the picture. Now that pixel that contains 25% blue box and 75% yellow background would register a light green to the display. The levels of anti-aliasing options simply allow the GPU to render larger scenes, thereby making more exact calculations as to the percentage of colors present in the single pixel, thereby allowing for a more accurate "average color" to display. Virtually, it's the same as playing in a higher resolution.

Now consider that with faraway objects there are quite a few colors getting mashed together into a single pixel space-- especially when the draw distance is high, or if the viewing angle is sharp. You may have dozens of different colors trying to average each other, and the result is a grayish, muddy mess. So the computer has to give precedence to colors(possibly to those "arriving" into the pixel space over the ones that are "leaving"). The visual effect is a more vibrant background, since like colors have a better chance of being separated than contrasting colors.