I've noticed in ATi tool they have section with driver tweaking, and I was wondering what "Temporal AA" is. Also with Catalyst A.I. level, is it better to have it high, low, or off?
What is Temporal Anti-Aliasing?
One of the impressive (but little discussed) features of ATi's R3x0 architecture is that it is capable of programmable AA patterns. Whereas most graphics boards only have pre-programmed sampling patterns, theoretically a developer (or indeed ATi themselves) could change to a different AA pattern whenever they chose. This feature has never really been explored by either ATi or developers... Until now, where it has become the basis for a new (and thus far only available via the registry) anti-aliasing mode.
So, how does it work? Basically, instead of using a single, static sampling pattern when AA is enabled, temporal AA allows the board to select from one of several patterns, which it can then switch between on a per frame basis. In other words, every rendered frame is antialiased slightly differently, using a different pattern. If at this point you are thinking that changing the pattern every frame would end up as a horrible, flickery mess, you'd be right. Until you examine the principle a little more closely that is....
What you need to remember here is that the user is not seeing a handful of frames every second, in most cases on a modern GPU you would hope to see some way over 60 frames per second being rendered by the card. When you reach these kinds of performance level, the changes in sampling pattern are happening so quickly, and so frequently, that the human eyes cannot detect the difference between the changes at all. Therefore, the eye sees all of the different patterns used to antialias the image at the same time, thus giving the impression of a higher level of AA than is actually in effect.
The one big potential caveat here is that if frame rates drop too low, then the effect becomes visible to the human eye and flickering will occur. Therefore, this new technique is obviously not going to be suitable for all titles, the user will need to pick and choose carefully those which will give sufficient performance for the method to function as it should. A side-effect of this is that V-sync has to be enabled when temporal AA is used (this is forced on in ATi's drivers when it is in use), and also requires a high refresh rate on your monitor to really do it justice (in the order of 100Hz seems to do the job nicely).