its very simple:
I have ATI Radeon. You go to control center of your graphic card. If not selected yet, use advance settings.
In the menu you search for 3D:
Now you play with the value's of Anti-Aliasing and Anisotropic Filtering to get the best texture quality in your game without losing too much of perfomance (PO)
Also have a check in your f1graphic.cfg file in your main gp4 folder. The file you can open with notepad or wordpad.
Check the lines:
5; [MAIN VIEW] Texture filter quality (0 => none, 1 => point, 2 => bilinear, 3 => anisotropic, 4 => flatcubic, 5 => gaussiancubic) v3
5; [MAIN VIEW] Texture filter quality for mipmaps - if any - (0 => none, 1 => point, 2 => bilinear, 3 => anisotropic, 4 => flatcubic/quincunx, 5 => gaussiancubic) v3
7; [MAIN VIEW] Max anisotropic filtering (1 => off, to max 7) v2
when i had an amd 64 bit 3000+ i had it set to 3/3/5 now that i have a dual core 4400+ its set to the highest level 5/5/7 !!!
So you have to play with the graphic card settings and the f1graphic.cfg file to get the best result for your pc's configuration !!!