Originally posted by Hellbinder
As I have pointed out over and over Anisotropic filtering was never intended nor appropriate for all angles. Primarily 90' and some others. This is a mathematical principle that is true even outside the graphics world.
And that's why you have an AAF (Adaptive Anisotropic Filtering) algorithm. Something that works along the lines of:
1. Classify each sample block to either edged, flat, or textured.
2. Classify each pixel - block class, spatial position, and distance from closest edge.
3. And then filter each pixel using some predefined discrete convolution according to classification.
That way you can account for nearly all the edges with your algorithm if you choose to. If you aren't going to account for anything other than parallel edges then there is no point in using AAF or even AF. If ATi have chosen to cut some corners in order to decrease the bandwidth requirements or increase algorithm speed then that's their design choice. But it definately doesn't make it more correct than an AAF algorithm that does account for more permutations.