Image Quality & Performance Comparisons
There is no hard and fast rule for precisely how much of a performance impact the various levels of AF and/or AA will bring with them, nor how much of a visual quality improvement you will see. It all depends on the particular game's resolution, your graphics card, and the complexity of settings and details in the game you are using.
To provide you with an indication of the type of image quality and performance impacts you can expect with different levels of AA and AF, I have compiled comprehensive screenshots of two recent games (one OpenGL and one Direct3D) running at progressively higher levels of AA and AF, and combinations thereof. Note that your performance will vary depending on how much more/less powerful your system is compared to the test system used.
Test System Setup
All the results shown in this guide were taken from games running on the following (non-overclocked) system:
Intel Pentium 4 2.66GHz
Asus P4G8X Deluxe Motherboard
Gigacube 128MB Radeon 9800 Pro AGP8x
1GB Corsair PC3200-LL
80GB Seagate Barracuda V SATA
Windows XP Professional SP1
3.10 ATi Catalysts
More details of the system here.
Aside from the AA and AF settings noted for each screenshot, the remaining settings in the ATi Control Panel were set to maximum possible quality, while VSync was set to Application Preference and TruForm and Fast Writes were off. The Windows XP install was optimized using my WinXP Tweaking: From Reformat to Relax guide, and no background applications were running aside from Hypersnap-DX5 (for taking screenshots) and FRAPS (for consistent measurement of framerates). The framerate for each screenshot is shown in the top right corner in yellow.
Note that despite the fact that these screenshots all come from a 9800 Pro, most objective reviews which have examined the issue of ATi vs. nVidia image quality generally consider that although nVidia cards generally have slightly better AF, and ATi cards have better DX9 image quality, the image quality is almost identical nonetheless. At the same time though, ATi and nVidia cards have (sometimes dramatically) different performance levels with AA and AF at different resolutions in different games. Therefore the results below should be fairly accurate indicators of image quality impacts for either brand of card when using the same AA/AF settings, but the performance impacts will vary, firstly on the brand of card you're using, and more importantly on how powerful it is.
For example a 64MB GeForce3 will not have the same performance as a 128MB FX5600 which in turn will not perform as well as a 128MB 9800 Pro. And since a 9800 Pro is one of the fastest cards available at the time of writing and its hardware is fairly optimized for AA/AF performance, most lower end and older cards will definitely experience much greater performance impacts than that shown below.
Finally, I don't want to enter into a long discussion or debate about which brand or particular card is better than another. That is beyond the scope of this guide. If you're interested in seeing how well all the various graphics cards perform, both with and without AA and AF, in a variety of games, take a look at this December 2003 article: Tom's Hardware VGA Charts III
It contains all the specifications, tables of results and rankings you need to figure out which card does what, and how fast, and help you determine which graphics card is best for your particular budget and gaming tastes.
On the next page are the screenshots and results for our first test game, America's Army.