Full-Screen Anti-Aliasing

Unlike the anisotropic filtering, GeForce FX can boast no drastic improvements in full-screen anti-aliasing. The only innovation here is the new 6xS and 8xS modes available only in Direct3D. These modes, as well as 4xS available since NVIDIA GeForce4, are a combination of multisampling and supersampling. To be more exact, it is supersampling applied to blocks processed by multisampling. Besides making textures look sharper due to supersampling, these methods should smooth polygons’ edges quite well thanks to the increased number of samples.

That’s what we are going to check out. ATI RADEON 9700 PRO is no simple rival: it uses a more interesting variation of multisampling when subpixels are placed on a rotated, not ordered grid. Our detailed examination of full-screen anti-aliasing implementation in ATI RADEON 9700 PRO is available in our ATI RADEON 9700 PRO Review.

So, we have our traditional scene from Serious Sam: The Second Encounter. We turned on work through Direct3D in game settings to enable 4xS, 6xS and 8xS modes of NVIDIA GeForce FX.

First, we check the quality of edges smoothing placed at an angle of 0^o and 90^o:

The method of 4x full-screen anti-aliasing from GeForce FX brings no surprises: the picture looks exactly like on any other graphics card from NVIDIA.

The 4xS method uses supersampling based on two blocks of 2x multisampling situated one above the other. That’s why it has a better effect on nearly-horizontal edges, rather than on nearly-vertical ones. In fact, there is no difference between 4x and 4xS on edges close to the vertical.

The 6xS method also uses supersampling based on neighboring multisampled blocks processed. But this time the blocks are situated horizontally, next to each other. This results in a better quality of edges smoothing if these edges are angled close to the vertical, but for horizontally angled edges this method works no better than 4x.

The 8xS method, just like 6xS, processes blocks placed horizontally next to each other. But due to the fact that it processes more samples (two blocks, four subpixels each), it is even more efficient in smoothing the “jaggies” at nearly vertical angles of inclination. As for horizontally angled edges, this method, just like 6xS, is hardly any better than 4x.

SMOOTHVISION 2.0 from ATI features rotated grid multisampling and provides excellent “jaggies” smoothing at polygons’ edges that are nearly horizontal or vertical. You can see it in the screenshots: in this case, 4x and 6x methods as implemented in ATI RADEON 9700 PRO don’t yield to NVIDIA GeForce FX in 6xS and 8xS modes.

Now, we change the angle:

Here 4x, 4xS, 6xS and 8xS modes of GeForce FX look better than 4x and 6x of ATI RADEON 9700 PRO: GeForce FX draws more half-tones at the edges of the polygons. The peculiarity of SMOOTHVISION 2.0 from ATI – the rotated grid – must have shown its disadvantage at these angles (30^o and 60^o) and these angles proved “inconvenient” for ATI RADEON 9700 PRO.

Now, the last variant:

We guess the “smoothest” edges are those produced by 6xS and 8xS methods of GeForce FX. All the rest, except ATI’s 2x, show a somewhat worse, but similar quality of “jaggies” smoothing.