Radeon HD 5870 reviewed: Voodoo 5 reloaded - Full Screen SSAA
Even more interesting and quite surprising than the improved AF is another feature that has been integrated besides Ati Eyefinity and DirectX 11 support. The AMD transparencies list it as a subordinate of the Raster Operators (ROPs) although some people might think it to be the most impressive feature of the HD 5800 series: The RV870 is capable of Sparse Grid Supersampling Anti Aliasing (SGSSAA). If you don't get teary-eyed now, let us explain this feature: The Anti Aliasing offered for other graphics cards by the drivers is based on Multisampling (MSAA) which only smoothes the edges of the polygons, but not the textures or pixel shaders. The latter ones dominate almost any surface in modern games and some shaders are not displayed perfectly although the best Anti Aliasing offered in the driver is activated. Here Supersampling comes into effect: Instead of sampling the polygon edges only multiple times, the whole scene is calculated again. The result is that the whole image is smoothed. SSAA also works against the mentioned "optimizations” of the texture filters. In our tests even 2x SGSSAA was enough to even textures and shaders to a acceptable level.

In the past Ati has regarded SSAA to be inefficient or "unsmart” - actually this is even true. There are several reasons that might have caused Ati to revise their opinion: Besides the already mentioned shader sins of modern games the many hardly hardware challenging console ports might have caused the rethinking. With Supersampling AA the spare calculation power of the cards can be used reasonably.

Experienced PC gamers might remember the year 2000, when 3D pioneer 3dfx introduce the VSA-100, also known as Voodoo 4 respectively Voodoo 5. The "killer-feature” of this graphics card series was Supersampling AA, which is used again today. With the Radeon HD 5800 the first graphics card series capable of 8x SGSSAA hits the mass markets. This Anti Aliasing mode has been, for nine years, a unique feature of the Voodoo 5 6000 which was never released officially.

SSAA in games
In comparison to the internal Oversampling, which can be forced on Geforce graphics cards with the tool Nhancer, the texture LoD is not adjusted with Ati's SSAA. To put it bluntly this means that the amount of AF is not increased. With a third party application like the Ati Tray Tools you can adjust the LoD by hand in order to receive the best texture sharpness. For 2x SSAA we don't recommend any changes yet, but for 4x SSAA you should set the LoD to -1 and for 8x SSAA -2 or -3 are flicker free - depending on the texture content.

Take a look at the comparison below that demonstrates the effect:

Click to select detail settings

8x MSAA/16:1 AF, LOD 0 8x SSAA/16:1 AF, LOD 0 8x SSAA/16:1 AF, LOD -2 (manuell angepasst)