View Full Version : Effects of super sampling AA on textures

01-12-04, 02:12 AM
NVIDIA has long offered hybrid anti-aliasing modes which utilize a combination of Multisamping and Super Sampling and even expose a few pure Super Sampling modes. Super Sampling is an older technique, mostly done in software on recent cards, which uses a lot of fillrate and memory bandwidth. Thus, in the worst case when the graphics card is the limiting factor for performance in games, Super Sampling takes a huge performance hit. Super Sampling has been superceded by Multisampling, which almost exclusively relies on memory bandwidth and has much better performance.

The problem with Multisampling is that it only does edge anti-aliasing and does not touch textures, whereas Super Sampling affects the whole screen, impoving textures and polygon edges alike. Enter anisotropic filtering. Anisotropic filtering is an advanced filtering technique designed to increase image quality in games by providing additional filtering of textures. Combined with Multisampling, the final image quality can be greater than that provided by Super Sampling alone, and the performance hit will be smaller as well. It would seem that Super Sampling is antiquated and has no further use with this information, but that isn't entirely true either. In fact, the hybrid Multisampling/Super Sampling FSAA modes provide the best FSAA edge quality available on NVIDIA cards.

Even though MSAA and AF may be an ideal coupling, SSAA still provides advantages that MSAA/AF do not. SSAA will reduce texture aliasing. SSAA will anti-alias alpha test textures which are commonly used in older games. In other words, SSAA will get rid of texture artifacts that still remain even when MSAA/AF are used like shimmering, pixel popping, etc. And SSAA does clear up textures, having an AF-like effect.

Granted, the hybrid modes have a hefty performance hit. In older games, they are perfectly usable. Surprisingly, even in some newer games they can be considered "usable" as we surely don't need 100+ frames per second in every game. You will have to try each mode yourself and determine whether you think the increase in image quality is worth the speed hit or whether you can even perceive the speed hit.

The point of this thread, however, is to examine the output of Super Sampling used together with anisotropic filtering. The following screenshots are taken with a texture filter test program and show what texture filtering benefits SSAA modes provide. The screenshots are organized by the SS component in each hybrid mode. Please note that some FSAA modes use the same SS component. For more information on hybrid modes and all FSAA modes NVIDIA cards support see [link not active- new thread coming soon!]

Anisotropic Filtering Only
0x AF (http://www.mrclam.com/~stealth/0xAF.jpg)
2x AF (http://www.mrclam.com/~stealth/2xAF.jpg)
4x AF (http://www.mrclam.com/~stealth/4xAF.jpg)
8x AF (http://www.mrclam.com/~stealth/8xAF.jpg)

1x2 Super Sampling (1x2SS & 4xS)
1x2 SS + 0x AF (http://www.mrclam.com/~stealth/0x1x2SS.jpg)
1x2 SS + 2x AF (http://www.mrclam.com/~stealth/2x1x2SS.jpg)
1x2 SS + 4x AF (http://www.mrclam.com/~stealth/4x1x2SS.jpg)
1x2 SS + 8x AF (http://www.mrclam.com/~stealth/8x1x2SS.jpg)

Modes using 1x2 SS are equivalent to having an additional 2x AF being applied at vertical angles only. Horizontal angles receive no benefit.

2x1 Super Sampling (2x1SS & 8x)
2x1 SS + 0x AF (http://www.mrclam.com/~stealth/0x2x1SS.jpg)
2x1 SS + 2x AF (http://www.mrclam.com/~stealth/2x2x1SS.jpg)
2x1 SS + 4x AF (http://www.mrclam.com/~stealth/4x2x1SS.jpg)
2x1 SS + 8x AF (http://www.mrclam.com/~stealth/8x2x1SS.jpg)

Modes using 2x1 SS are equivalent to having an additional 2x AF being applied at horizontal angles only. Vertical angles receive no benefit, so you can imagine that this is not going to be a good choice at all for games as AF's most notable effect is in clearing up textures in the horizon.

2x2 Super Sampling (4xSS & 8xS)
needs to be added
4x SS + 2x AF (http://www.mrclam.com/~stealth/2x4xSS.jpg)
4x SS + 4x AF (http://www.mrclam.com/~stealth/4x4xSS.jpg)
4x SS + 8x AF (http://www.mrclam.com/~stealth/8x4xSS.jpg)

Modes using 4x SS are equivalent to having an additional 2x AF being applied. 4x SS with 8x AF is equivalent to the results of 16x AF, if NVIDIA provided such an option. This has the best increased image quality of all modes using Super Sampling, and as you can see, it is actually better than the equivalent AF option!

1.5x1 Super Sampling (6x)
6x + 0x AF (http://www.mrclam.com/~stealth/0x6x.jpg)
6x + 2x AF (http://www.mrclam.com/~stealth/2x6x.jpg)
6x + 4x AF (http://www.mrclam.com/~stealth/4x6x.jpg)
6x + 8x AF (http://www.mrclam.com/~stealth/8x6x.jpg)

6x provides extra filtering on horizontal angles. The amount of filtering is somewhere between 0x AF and 2x AF.

1.5x2 Super Sampling (12x)
12x + 0x AF (http://www.mrclam.com/~stealth/0x12x.jpg)
12x + 2x AF (http://www.mrclam.com/~stealth/2x12x.jpg)
12x + 4x AF (http://www.mrclam.com/~stealth/4x12x.jpg)
12x + 8x AF (http://www.mrclam.com/~stealth/8x12x.jpg)

12x provides the same filtering on horizontal angles that 6x does, something between 0x AF and 2x AF. On vertical angles the filtering is equivalent to 2x AF.

The results of the synthetic test really tell us all we need to know. However, I realize that some people have an easier time grasping actual shots from games, or place a higher priority on results attained "in the real world." I will provide some of those too, albeit not nearly covering as many options as shown with the synthetic test. Screenshots were taken using Serious Sam: The Second Encounter with the Direct3D renderer so all FSAA modes could be used. The purpose is to compare texture quality and not edge quality so 640X480 was used to save on file size. All shots are presented as .jpgs, but there's no need to worry as there is little difference between them and the uncompressed images; everything that I intended to show is clearly visible and the only changes are a few slight compression artifacts and a dimming of colors on some textures. One thing to keep in mind is that these shots illustrate vertical angles, so they don't tell the whole story. Of course, the predominant angles in games are vertical since you always have a point of view from a fixed point.

Serious Sam Anisotropic Filtering Only
0x AF (http://www.mrclam.com/~stealth/Sam0x.jpg)
2x AF (http://www.mrclam.com/~stealth/Sam2x.jpg)
4x AF (http://www.mrclam.com/~stealth/Sam4x.jpg)
8x AF (http://www.mrclam.com/~stealth/Sam8x.jpg)

Serious Sam 1x2 Super Sampling
2x1 SS + 0x AF (http://www.mrclam.com/~stealth/Sam1x2AA.jpg)
2x1 SS + 8x AF (http://www.mrclam.com/~stealth/Sam1x2Max.jpg)

Serious Sam 2x1 Super Sampling
1x2 SS + 0x AF (http://www.mrclam.com/~stealth/Sam2x1AA.jpg)
1x2 SS + 8x AF (http://www.mrclam.com/~stealth/Sam2x1Max.jpg)

Serious Sam 4x Super Sampling
4x SS + 0x AF (http://www.mrclam.com/~stealth/Sam4xAA.jpg)
4x SS + 8x AF (http://www.mrclam.com/~stealth/Sam4xMax.jpg)

Serious Sam 6x
6x + 0x AF (http://www.mrclam.com/~stealth/Sam6xAA.jpg)
6x + 8x AF (http://www.mrclam.com/~stealth/Sam6xMax.jpg)

Serious Sam 12x
12x + 0x AF (http://www.mrclam.com/~stealth/Sam12xAA.jpg)
12x + 8x AF (http://www.mrclam.com/~stealth/Sam12xMax.jpg)

01-12-04, 04:44 AM
Er... nice work :D.
I was wondering, does the 4xS AA mode use SuperSampling or is it a combination of MS & SS ?


01-12-04, 07:50 AM
Nice work there, StealthHawk. Hopefully some of the people that were arguing against ATI implementing SSAA in their future drivers see this, since it seems that many of them don't really 'get it' when the rest of us explain why the feature has such potential usefulness. (Sorry for sidetracking the nV forum with meantion of ATI- it's just that this is directly on topic for that discussion too, and does illustrate well one area where nVidia definitely leads..)

01-31-04, 08:52 PM
nice works, had to lower my res to look at the pictures, at 1600x1200 those pics were something like 4x3 cm ;) not enough to notice any quality differences at least :)

02-26-04, 04:17 PM
Originally posted by mrsabidji
Er... nice work :D.
I was wondering, does the 4xS AA mode use SuperSampling or is it a combination of MS & SS ?


And....the answer can be found here (http://www.nvnews.net/vbulletin/showthread.php?s=&threadid=25401)!

Yeah, 4xS is a combination of MS & SS.

03-15-04, 04:33 PM
late thanks ;).