[prankstare]

Originally Posted by jlippo

Yes, what it does is sample textures multiple times to get better quality.

Basically it samples the trapezoidal area on texture/polygon covered by the pixel.
More samples on that area/mipmaps better the quality and this is why there is different levels on AF.

Using AF does not use more memory as mipmap pyramid already has 'bloated' textures by 0.33 already when using mipmapping/trilinear filtering.
This thread is goldmine for information about anisotropic filtering.

I would also suggest on going to the source, when wanting to learn about consoles and reasons why developers do things like they do.
http://microsoftgamefest.com/2006.htm (note. clicking links downloads ALL presentations of graphics, audio... and so on.)
http://microsoftgamefest.com/presentations/2007.htm (just normal single presentation links.)
http://microsoftgamefest.com/presentations/2008.htm
http://microsoftgamefest.com/seattle2010.htm

For Cell on ps3, one only needs CellBE Handbook.

jlippo, thanks for the clarification. But how do you explain the fact Xbox 360 almost never uses any anisotropic filtering in their titles and PS3 does? If Xbox clearly has "better" graphics hardware, including the super-fast EDRAM, why would developers sacrifice AF on this console? For the sake of FPS? I don't think so. For the 4xAA + HDR? Maybe? I thought this was a matter of disc storage space (dvd9 vs. blu-ray), but you said AF has nothing to do with memory, so I am more and more confused.

Take this comparison video for instance: when you look at the ground, you see there are much more detailed graphics for the PC version of the game. Is that AF, tesselations or simply more graphics objects?