SLI Antialiasing Preview

[ChrisRay]

SLI Antialiasing Preview

Introduction SLI AA : There are some instances where SLI can find it self CPU Bound under various circumstances. Or in even the worse case scenerios where SLI does not prove to provide any performance benefits at all. The general idea of SLI AA is that it will work in everything. Without the need for a profile while providing an immediate benefit to all your current games. It does this by using both graphic cards to sample the scene and joining the final image.


How to enable

Step 1: First thing you'll need to do is install coolbits. You can get coolbits from several places such as SLI Zone or this direct download.

Step 2: You'll need to enter your advanced settings as if you were going to setup a SLI Profile. From here you'll see a new SLI rendering known as SLI AA. Once you select this mode you should be able to return to your AA configuration and find two new options. Namely SLI 8x and SLI 16x.

Note: SLI AA is not compatible with previous modes of SLI rendering. There will not be an improvement in rendering performance. This is a quality improvement mode.









8xS AA verses 8xSLI AA

8xS AA: This mode has been available to Nv4x users for sometime. It combines 1x2 Super Sampling to with 4x RGMS and creates a fairly ideal result. Unfortunately this mode consumes significant amounts of bandwith and pixel fillrate to operate. This mode is available to all Geforce 6 + cards.



SLI 8xAA: SLI 8xAA operates a bit differently. It does so by taking a 4x RGMS on each card and combining them together. Notice the super sampling portion of 8x SLI is Rotated Grid. This could provide an excellent image quality enhancement to standard 8xS. This is an SLI specific mode.





16xS verses 16x SLI AA

16xS AA: The first 16xS AA mode ever available in a direct3d enviroment. This mode combines 2x2 OGSS and 4x RGMS. This mode is very fillrate/bandwith/framebuffer intensive and can send even 7800GTX SLI cards to their knees. Another limitation is that it cannot go beyond 1280x1024 resolution due to framebuffer requirements. For this reason it was not included in todays benches. This mode hidden and requires a registry tweak to be enabled.



SLI 16xAA: This mode is fairly interesting. It is done by two cards rendering a 1x2 super sampling with 4x RGMS similar to the original 8xS mode. However like the 8x SLI mode it the samples are combined individually on the two cards and then rendered to to the final image. Notice the super sampling portion contains a slight shift from an ordered pattern. This mode is only available to SLI users.



Note: From a quality perspective the new SLI modes are comparable to the old xS counterparts with minor variances in quality due to the differences in sample patterns. You can find some older quality comparisons done here.

Guild Wars Quality Screenshots

4xAA/16xAF

http://www.nvnews.net/articles/chris...x/gw4xnorm.png

SLI 8xAA/16xAF

http://www.nvnews.net/articles/chris...tx/gw8xsli.png

SLI 16xAA/16xAF

http://www.nvnews.net/articles/chris...x/gw16xsli.png

SLI 16xAA/16xAF (Transparency SuperSampling)

http://www.nvnews.net/articles/chris...ansparency.png


Far Cry Performance






Performance Notes: As I mentioned before. Unlike previous SLI rendering modes SLI AA modes are not meant to improve performance. They are meant to provide an image quality enhancement to people with dual graphic cards. In the case of SLI 8xAA you will see a performance bonus over 8xS in single GPU rendering. 16xS AA however is an incredible edition and can be used practically in many olders titles @ 1600x1200 with 7800GTX cards in SLI. It can also be used in many current titles @ 1280x1024 and below with a 7800GTX SLI setup.


Thoughts and Conclusions: When I was first told about SLI AA. My first thought was. "Whats the Point?". But after giving it some thought and seeing it in action. Theres alot of useful ways to benefit from it. Especially in older titles which dont scale with SLI due to CPU limitations. In the end you are just provided with more options. And who can argue with options? They produce excellent image quality and will allow SLI users to get more value from their setups. Kudos to Nvidia.

Final Note: I did not take any screenshots due to the unfortunate bug of it not being capturable with fraps. I have been informed that this bug is being worked on. A couple of comparison images are below. Please take note that these were not taken by me.

http://www.nvnews.net/articles/chris.../bf2_fence.gif

http://www.nvnews.net/images/screens...exterior_2.gif

http://www.nvnews.net/articles/chris...im_tower_2.gif

MUYA : Fixed them screens

[ChrisRay]

Sorry this preview isnt as big. It was done on very short notice and there were also alot of technical restraints which prevented me from doing everything I would have liked.

Hopefully you can still find it informative and valuable.

[Sazar]

Which game did you test?

Nice info btw, hopefully you can grab a few screens later with a workaround.

[ChrisRay]

Yikes! I didnt list the Far Cry Title title! Wow.. all nighter.. what a screwup.

[Edge]

Interesting stuff, I thought multi-GPU AA was an interesting feature when I read it was going to be part of ATI's Crossfire, nice to see that Nvidia has added it to SLI as well. Hope to see some screenshots soon (once the bug is fixed...doesn't print-screen work either?), I'd like to see what kind of actual effect this has on image quality. Also, this makes me wonder how SLIed 6600gt cards would compare to a single 6800gt with both running the equivalent AA modes (8xS/8xSLI and 16xS/16xSLI).

[Sazar]

Originally Posted by ChrisRay

Yikes! I didnt list the Far Cry Title title! Wow.. all nighter.. what a screwup.

Lol, I read it about 5 times just to be sure. I'm in the same boat, not slept all night, everything all insane in da membrane.

[ChrisRay]

For those interested in screenshots. Please check out these animated Gifs. They are "Not" mine. But they were provided to to help illustrate the benefits of 16xAA.

http://www.nvnews.net/images/screenshots/bf2_fence.gif

http://www.nvnews.net/images/screens...exterior_2.gif

http://www.nvnews.net/articles/chris...im_tower_2.gif

[wEEt]

Performance hit seems to be pretty big but I guess it's the best IQ we've ever seen That's what SLI is there for...

Holy ****, 16xSLIAA looks amazing

[BrianG]

Going to try SLI 8X on the 6600GTs with Q3A and UT 2K3 when I get home. Hmm, 7800GTs in HL2 with SLI AA...

Hey Chris is there a transparency setting for 7800GTX still? Does the frame buffer combine apply AA to the Alphas?

[ChrisRay]

Originally Posted by BrianG

Going to try SLI 8X on the 6600GTs with Q3A and UT 2K3 when I get home. Hmm, 7800GTs in HL2 with SLI AA...

Hey Chris is there a transparency setting for 7800GTX still? Does the frame buffer combine apply AA to the Alphas?

Yes transparency options still work with SLI AA.

[Sazar]

Looks really nice

How playable was Far Cry when you were running around? Its not a run and gun type game per se but was it chugging in spots?

[ChrisRay]

Originally Posted by Sazar

Looks really nice

How playable was Far Cry when you were running around? Its not a run and gun type game per se but was it chugging in spots?

At 1280x1024 @ 16xAA far cry was entirely playable. It was a grey area at 1600x1200 though. All things considering though I think thats still pretty darn good.