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Image Quality Showdown: ATI vs NVIDIA August '06 August 22, 2006 |
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Summary: In this article, Brandon and Jakub take a closer look at the visuals produced by ATI and NVIDIA's latest graphics cards. Not only do we compare baseline AA image quality, but we're also going to compare ATI's adaptive AA with NVIDIA's transparency AA to see how well they live up to the hype. Finally we'll address the issue of texture shimmering by including actual gameplay video footage in Battlefield 2. Is it really a problem or is it an overblown topic? Judge for yourself after reading this article!
 Introduction | Page:: ( 1 / 6 ) |
Performance isn’t the only aspect that’s used for measuring the success of a graphics card though. Equally important is the image quality of the graphics card. It’s here where things can get tricky very quickly, as judging image quality can be very subjective. What looks terrible to one person, may not be noticed by a second person; what looks “great!” or “excellent!” to one may only look “good” to another. Often times, there isn’t a very fine line separating the two, it’s more like a very subtle marker with no defined boundaries.
Today we’re going to tackle the image quality (IQ) offered by today’s latest graphics cards from ATI and NVIDIA. We’re going to do things a little different this time around though and offer more than just screenshots to compare IQ. We’re doing this because we want to take a closer look at one recurring topic that continues to come up from time-to-time: texture shimmering.
Texture shimmering
What is texture shimmering you ask? As a quick refresher, texture shimmering can occur when the mipmap transitions from one texture resolution to the next. If the transitions are harsh, the lower quality mipmap levels can stand out pretty dramatically; this sometimes causes a shimmering or flickering effect to the eye. In some extreme cases, you’ll practically see a line ahead of you marking the spot between these transitions. Ideally the higher detail textures should blend well with the lower detail textures and the end user shouldn’t notice a thing, but unfortunately this hasn’t always been the case.
In any case, going back to our original point, what we’ve found with texture shimmering is that it can be highly variable. You may never see it in one level of a game, and then in the next it’s impossible to miss it. In general texture shimmering is harder to spot in dark areas, and easiest to spot in bright, outdoor areas with long, flat surfaces. In this scenario texture shimmering can be very easy to spot, as textures on the ground in front of you are literally flickering before your eyes.
What makes texture shimmering really tricky though is that it can sometimes be incredibly difficult to spot in a static screenshot, and static screenshots are the #1 tool used by hardware reviewers to judge image quality. It’s easier to spot when you’re up and running in motion. Because of this, we’re going to rely primarily on videos, rather than screenshots, to spot texture shimmering.
| System setup | Page:: ( 2 / 6 ) |
Intel Core 2 Extreme X6800
ASUS P5W DH Deluxe (for ATI system)
ASUS P5N32-SLI SE Deluxe (for NVIDIA system)
NVIDIA GeForce 7900 GTX 512MB
ForceWare 91.33
Unannounced upcoming ATI graphics card
Catalyst 6.8
Control panel for all cards left at default settings
Windows XP Professional with Service Pack 2
DirectX 9.0c
Benchmarks
3DMark 06
Half-Life 2
Call of Duty 2
Notes
Armed with the GeForce 7900 GTX and ATI’s latest Radeon graphics card, we set out to evaluate the IQ delivered by both manufacturers high-end products. We should note here that while we’re only looking at the IQ of two graphics cards, ATI and NVIDIA apply the same graphics optimizations used in these cards to the rest of the products in their respective graphics lineup, so the images we’re displaying here also apply to other cards such as the X1900 XTX or X1900 XT/GT, X1800s, etc from ATI, as well as the GeForce 7800/7900 GT/GTX.
We’re sticking with the default control panel optimizations for both manufacturers except when using transparency AA/adaptive AA. In that case, we used ATI’s “Quality” setting for adaptive AA (which forces the use of supersampling to improve IQ) and NVIDIA’s “Super-sampling” setting for the GeForce card. We also turned on gamma correction for AA in this case as well.
With that being said, let’s take a look at some screenshots!
| CoD 2 Image Quality | Page:: ( 3 / 6 ) |
CoD 2 0xAA 16xAF
The first difference is one we’ll spot consistently throughout the Call of Duty pictures. If you look at the telephone pole and directly left of it, at gun height, you will spot that the mortar in the brickwork on the NVIDIA shots is somewhat clearer and definitely a shade or two brighter. The shadow in the doorway on the left side of the screen is also darker on the ATI screen. This may be a gamma setting issue, but we’re inclined to disagree given that the textures are otherwise pretty much identical in brightness.
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The results of the anisotropic filtering differences are intriguing. If you look directly to the left of the crates, where the road snakes up and away, on the ATI screen it looks smooth, but the NVIDIA image shows slight dimples indicating that the card is still trying to draw the gaps between the stones. This small advantage in favor of NVIDIA is arguably offset by the relatively drastic change in filtering on the cobblestones, alongside the lower arm of our avatar, just above the cufflinks and below the end of the sleeve. It’s interesting because both methods of filtering start the same, NVIDIA gains the edge in sharpness at the cufflinks, but suddenly transitions to a lower filtering mode due to their default optimization scheme. In screenshots, it can be argued either way – that the sharpness offsets the transition, but in motion, as you’ll see on the videos, the NVIDIA optimizations create a texture flashing/pixel crawl effect that can be distracting to some viewers.
CoD2 4xAA 16xAF
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In our AA-enabled screenshots, we see the above results and of course the differences in AA algorithms. Generally they’re both very competitive with each other, but there are two slight differences, both along the telephone cables running above the battlefield. Specifically, near the hanging lamp, the ATI card does a poorer job of hiding the steps in the cable, while the NVIDIA card produces a nearly-smooth image. The top wire, after passing the far telephone pole, is also clearer on the 7900GTX as it passes from the pole through a brief section of sky before disappearing into the roof of the far house. On the other hand, ATI clearly does a better job with the same cable when it passes over to the house on the left as it curves upwards. Here we see more jaggies with NVIDIA than ATI.
CoD 2 4/6xAA 16xAF Transparency/Adaptive
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When we turn on Transparency AA and Adaptive AA for both cards, we see the same results as above, but with changes to the fence on the left. It loses some brightness with both methods, though the Adaptive AA on the ATI upcoming card seems to handle things somewhat better, and continues to draw the fence almost to the end, unlike the GeForce. Otherwise, pictures are identical and neither card gets help with the jaggies on the telephone cables.
The best image quality, bar none, is delivered by ATI in its 6xAA 16xAF mode with Adaptive AA turned on. It finally gets rid of the jaggies along the telephone cable, does the best job of all with the fence. The only areas where it lags somewhat behind NVIDIA is in the stone pattern behind to the left of the crates, and the mortar and brickwork to the left of the closer telephone pole.
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| Half-Life 2 Image Quality | Page:: ( 4 / 6 ) |
HL2 0xAA 16xAF
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Though moderate, the advantage clearly goes to NVIDIA in this comparison. It draws more of the chain-link fence, especially on the left side, and the skinny branch on the far side of the close tree is more visible. The far tree is also a good indicator, especially if you can display the images side-by-side or save them on your desktop and flip through them.
HL2 4xAA 16xAF
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In both cases we see essentially the same results as before, except the margin is slimmer though still in NVIDIA’s favor. The upcoming ATI card does a better job than the GeForce now around the middle of the fence, though the far left and the trees still go in NVIDIA’s favor.
HL2 4xAA 16xAF Transparency/Adaptive
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NVIDIA’s GeForce 7900 GTX takes the lead here as Transparency AA clearly does a better job in this scene. The fence is clearer and more robust, the major advantage is in drawing the far tree. The close tree also shows considerably more of the skinny branches, especially on the right-hand side.
HL2 ATI 6xAA 16xAF Adaptive AA
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This is a tough one. On the one hand, ATI’s fence is remarkably smooth and free of missing pixels or jaggies. On the other, it is even more faded now. Overall though, advantage ATI on the fence. When it comes to the trees, despite the move to 6xAA, the ATI product still cannot render as many of the thin branches as the 7900GTX. What is show, individually, tends to look better on a branch-by-branch basis, but the extra fullness of the tree in the GeForce pictures is tempting. We’re going to mark this test as a wash. It’s not that either card is better, but we expect personal preferences regarding the trees and fence are going to be especially important.
| 3DMark Quality and BF2 Video! | Page:: ( 5 / 6 ) |
0xAA 16xAF
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This was the most difficult comparison to spot a difference in. The best area to look is on the fronts of the crates, especially the one on the left side where the trooper is taking cover. You’ll see on the front of those crates little gratings or vents near the top of each. On the GeForce cards they are slightly more prominent, but this difference is almost insignificant and these pictures merely serve as a baseline for the AA pics.
4xAA 16xAF and ATI 6xAA
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We have ATI 4x and 6x AA with 16xAF and NVIDIA 4xAA 16xAF screenshots to compare here, and again, it is almost impossible to tell a difference. Once again the only place that strikes the eye is the little vent or grating on the front of each crate, where the dark parts appear darker on the NVIDIA cards for better contrast. Otherwise, the images appear identical, even with 6xAA on.
Battlefield 2
EDIT 8/24: We've removed the BattleField 2 screenshots of the ATI and NVIDIA cards as this test relies on the AF videos presented below.
Right click on the thumbnails and select Save As to save the videos to your PC. (Note:You'll need to download and install FRAPS to watch the videos)
For Battlefield 2 we use video to show the texture flashing effect which occurs in motion due to NVIDIA’s optimizations. It happens in two areas, horiztonal lines a couple of dozen pixels thick, both below the crosshair. The first is directly below the bottom hair, the second is about 10% of the video below that. The problem with the optimizations and the pixel crawl/texture flashing they induce is not that it exists, but that it’s the most subjective of all things there. When you watch the video it is clearly happening and quite annoying, but have you ever noticed it when playing a game? Would you even notice if Brandon was doing an action shot rather than run-through, if there was sound and explosions and communications going on? Of course, this doesn’t change the fact that when you do see it, it is rather glaring.
Finally, it can be disabled. NVIDIA provides an option in its driver panel to disable the optimizations (at some cost in performance). Why don’t we test with it disabled then? Because most people run drivers at default or nearly default settings, because even with the optimizations turned off, it’s still not a direct comparison to the way ATI does things. Just like 4xAA looks different on an ATI card than an NVIDIA one, so too do unoptimized filtering methods. Quite frankly, if the card manufacturer feels comfortable with the optimizations turned on, knowing they’ll get discussed in an article, we’re happy to oblige.
You’ll notice that this is not something that is evident in the screenshots we present above. It is only when we take video that it becomes clear.
| Conclusion | Page:: ( 6 / 6 ) |
NVIDIA’s anisotropic filtering looks better in screenshots. You’ll remember that you can see the cobblestone pattern in the Call of Duty 2 screens far beyond where the ATI image blurs them into flat ground, but this comes at a steep price. NVIDIA’s optimizations create the shimmering effect we saw in the Battlefield 2 video, which can range from unnoticeable to distracting, depending on the game, the scene, and how sensitive you are to it. Also, the optimizations produce a sharper point of delineation where the card switches from low detail to high detail textures, creating clear steps of detail change relative to the smooth transition of ATI’s upcoming hardware. ATI’s own optimizations aren’t without fault either, as some users have reported shimmering with ATI’s latest cards as well, but as you can see in the videos, it isn’t nearly as pronounced, even in our scenario outlined with Battlefield 2.
Of course, when you’re playing a game, whether it’s something slow-paced like World of WarCraft, or a fast-paced shooter like Half-Life 2, it’s up to you to decide what matters most. Are you going to notice the NVIDIA optimizations? Is turning them off going to make it better for you? Are you going to prefer ATI’s generally smoother 6xAA or the better boldness and contrast of NVIDIA’s 4x technique? Or, let’s be honest, with differences so small, are you going to go for the card that gives you the best value? Only you can answer the questions for yourself, we just give you the results of our tests to help in your choice.
Finally, a warning and a caveat: many of the images we have shown, and the ones most readers focus on are the cropped versions with commentary. It’s easy to focus in those on that tiny little portion of the screen, especially when we increase the magnfication to help explain what we see. Remember, this is not what you see on the screen. You see the whole screen, you see it in motion, you don’t see it magnified. Look at the cropped cutouts, enjoy the detail, and then go back to take a look at the full version image so you don’t miss the forest for the trees. The little details only add up to create the final picture, they don’t define it. We should also add that judging image quality is a much more subjective field than judging performance. Again, look at the screenshots, watch the videos, and then decide for yourself which card delivers the best combination for your eyes.
We’re considering adding a second part to this article. If you have any feedback/suggestions or things you’d like to see, let us know in the news comments!
UPDATE 8/23/06: Now that the NDA for the X1950 XTX has expired, you can see the benchmarks delivered by these IQ setups in our Radeon X1950 XTX Performance Preview article. In Part 2 we'd like to explore the control panel options offered by ATI and NVIDIA in more depth, rather than sticking to the basic settings. Be on the lookout for that article in the weeks ahead.