Original Link: http://www.anandtech.com/show/1708



NVIDIA Announces 16x AA For SLI

In response to ATI's CrossFire launch, NVIDIA has revisited a few points about their own solution, as well as revealed some sneak peeks into the future of their SLI technology.

Of course, one of the key points NVIDIA wanted to make was that their game support is no less than ATI's. Initially, either games needed profiles setup in order to run, or users had to know how to hack the NVIDIA XML file. NVIDIA is now offering the ability to enable user selected SLI modes for games that do not have profiles. Profiles will take precedence over user selected modes, but even games whose profiles disable SLI will allow the user to force it on.

Their other real point of contention with ATI is their claim that they add quality options where NVIDIA does not. As we know, ATI is enabling 10xAA and 14xAA options for games that don't see any real benefit from SLI otherwise. In order to top the announcement that ATI made, NVIDIA has revealed that they are planning on bringing out a 16xAA mode via SLI in a driver to be launched in early July.

We haven't gotten as much detail about this implementation as we currently have on ATI's AA modes. We don't know what the final sample point patter will look like, but NVIDIA has said that they will provide this detail when they finalize it themselves. We do know that, regardless of what NVIDIA decides, their 16x mode will be a combination of 4x multisampling and 4x supersampling. The debate currently is whether or not to implement supersample AA via an increased resolution or by rendering the scene 4 times with each rendering being slightly shifted. The advantage of the latter method is that rotated grid SSAA can be used, but the disadvantage is that the geometry load would be increased. NVIDIA has told us that they can do either method but haven't decided which to settle on.

Why is 4xSS plus 4xMS equal to 16xAA? Because each supersample point contains 4 multisample points giving us 4 times the multisample points. The other advantage is that SSAA applies to the entire scene, so we get 4xSSAA applied to parts of the scene that would see no benefit from multisampling (the interior of polygons and textures).

This mode will not be a simple combination of two scenes rendered with the current 8xAA, but rather each card will render 4xSS + 4xMS. For alternate and split frame rendering, each card will be doing full 16xAA. This may also give us a glimpse into the future as each generation graphics cards continue to increase in power. Doing full 16xAA on each card means we could see this order of AA running on a single card in a generation or so.

We are definitely interested in testing this mode when it comes along early next month.

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