Anisotropic filtering is a bit more complicated than AA. It deals with one of the most glaring and inherent flaws of 3D gaming: Painting a 3D image onto your 2D monitor screen. A little bit of background information here is needed. Every pixel on your computer screen has several X and Y texture elements, or ‘texels’, associated with it. Until the invention of AF, these textures where computed using an isotropic, or cubic, method.

A shallow plane of characters showing the distortions of purely isotropic filtering

Now, this method works best where you are looking at an object directly perpendicularly, from above. In other words, it works best on a 2D setting. If you start to change your angle of viewing until it is around 30 to 20 degrees, the video card needs to use a non-cubic texture filter to maintain proper clarity, because it is going to be processing much less information on the X or Y axis. That is where AF comes in to play. To put it simply, it is a non-isotropic filtering technique, or, An-isotropic filtering. This uses several different geometric shapes, depending on the angle, on each pixel to determine the clearest representation of the images. In fact, ATi’s 16x AF program uses 128 shapes per pixel to produce clarity at a low-angle perspective. The result, seen in this image courtesy of ATi, is quite staggering. ATi AF flavors come in 2x, 4x, 8x, and 16x, while nVidia offers 1x, 2x, 4x, and 8x. The numbers indicate how many different shapes are used in order to determine the proper pixel texture. This process sucks up a decent amount of ram bandwidth, so obviously turning it on gives you a performance hit. Once again, those who crave FPS ought to avoid AF, but for people like me, AF is where it’s at. The performance hit you could expect with AF and AA both at full blast is a bout 20-25%, slightly less if you have an ATi X800-series card, which have specially designed AA and AF pathways.

The same plane, now with 16x anistropic filtering applied

Well, it’s about time to take a break from the confusing realm of AA and AF and explain the (relatively) simple concept of vertical sync. Every monitor has a refresh rate on it, which goes down as your crank up the resolution. The best monitors have a refresh rate of about 100Hz at 1280x1024 resolution. This means it paints a new image on the screen 100 times in one second. However, video cards can generally produce much more than just 100 frames per second. This generates a bit of a problem where the next image starts getting drawn on the monitor before the first image is finished. Assuming you had a killer system and where running quake 3 at 800x600, you’d probably be getting 500 FPS. This means that at any given time, there are five different images being painted on your monitor. What vsync does is it binds your FPS to your monitor’s refresh rate, so that the highest FPS you can possible achieve is equal to the refresh rate your monitor is currently set at. Hence, it syncs the graphics card image with the monitor image.

Though I could go on and on all day long about the different video card settings, these appear to be the most major, at least with respect to image quality. So the next time you play your favorite games, and FPS isn’t an issue, try out these neat little video card tricks and find out if you like what you see. Believe me, sometimes the difference is like night and day. So give it a shot; see what you think.