NVIDIA's GeForce 8800 (G80): GPUs Re-architected for DirectX 10
by Anand Lal Shimpi & Derek Wilson on November 8, 2006 6:01 PM EST- Posted in
- GPUs
What's Transparency AA?
Transparency AA is NVIDIA's method of applying AA to transparent textures. Because MSAA only looks at one texture sample per pixel per polygon where more than one polygon slices a pixel area, it is not able to smooth jagged edges in transparent textures. In order to combat this, NVIDIA applies supersample AA to transparent textures. Their multisample transparency AA really doesn't do much for visual quality, so we will be ignoring it today. It only allows multisample through transparent texture areas and not of the texture itself.
Supersample AA performs a texture lookup at each sub-pixel to determine how much of the pixel falls on a transparent area of the texture and how much falls on an opaque area. The analog in ATI hardware is called Adaptive AA, which does basically the same thing. This generally has a very large performance impact for 3D scenes with many transparent textures (fence, bushes, leaves, and the like).
All screenshots on this page are 400% zooms of the highlighted portion of the following Half Life 2 screenshot:
Here's a look at Half-Life 2 with and without Transparency AA. We can clearly see how the leaves of the trees get smoothed out and look much better.
G80 No Transparency G80 Transparency AA
Hold mouse over links to see Image Quality
When comparing G70, G80, and R580, we have to remember that for NVIDIA hardware we've disabled gamma correct AA. It isn't possible to do this on ATI hardware, and thus we have a comparison of gamma correct AA on transparent textures as well.
G70 4X No Gamma G80 4X No Gamma ATI 4X Gamma
Hold mouse over links to see Image Quality
G70 and G80 don't look that different, but the R580 creates a kind of mushy look around the trees. This is another side effect of gamma correct AA and its potential negative impact on image quality. Worse examples include wire mesh or fences built with transparent textures: gamma correct AA can end up making parts of a fence disappear. Ideally, if we could apply gamma correct AA to high contrast edges and disable it for everything else, we'd see an image quality improvement. But the downsides just keep piling up with thin lines and transparent textures causing problems for gamma correction.
While transparency AA does enhance image quality a good deal, we do need to consider the performance impact. We'll revisit our antialiasing scaling graph from our CSAA page with Transparency and Adaptive AA enabled.
With G80, we see great performance at high resolution with high levels of AA while Transparency AA is enabled. With this level of performance, as long as R600 is able to keep up, we would love to check the Transparency AA check box every time we test with AA. For now, the performance degradation in R580 is just too high to justify at resolutions over 1600x1200 in most cases. An increase in resolution to a comparable performance level will net a higher gain in image quality.
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Sunrise089 - Thursday, November 9, 2006 - link
Then I suppose he's in the market to part with an ugly old high-end CRT. I'd love to buy it from him. Seriously.JarredWalton - Thursday, November 9, 2006 - link
You want an older 21" Cornerstone CRT? It's a beast, but you can have it for the cost of shipping (which unfortunately would probably be ~$50). I'd also sell my Samsung 997DF 19" CRT for about $50, and maybe an NEC FE991-SB for $50 (which unfortunately has a scratch from my daughter in the anti-glare coating). If anyone lives in the Olympia, WA area, you know how to contact me (I hope). I'd rather someone come by to pick up any of these CRTs rather than shipping, as I don't think I have the original boxes.DerekWilson - Thursday, November 9, 2006 - link
lol next thing you know links to ebay auctions are gonna start showing up in our articles :-)yyrkoon - Thursday, November 9, 2006 - link
lol, I've got a 21" techtronics I'll sell for $200 usd, plus shipping ;) Hasnt been used since I purchased my Viewsonic VA1912wb (well, been used very little ).imaheadcase - Wednesday, November 8, 2006 - link
can't stand AA benchmarks myself :)Question: Do you have any info on what kinda card nvidia releasing this feb? Is it something in between these 2 cards or something even lower?
Im looking for a $300ish g80! :D
flexy - Wednesday, November 8, 2006 - link
if ANYTHING counts then how those high-end cards perform WITH their various AA settings.... the power of those cards (and the money spent on :) RIGHT translated into ---> IMAGE QUALITY/PERFORMANCE.Please dont tell you you would get an G80 but do NOT care about AA, this does NOT make any sense...sorry...
I am especially impressed reading that transparency AA has such a LITTLE performance impact. What game engine did you test this on ?
On the older ATI cards (and am i right that T.A. is the same as "adaptive antialiasing" ? )...this feature (depending on game engine) is the FPS killer....eg. w/ games like oblivion (WHERE ARE THE GOTHIC 3 BENCHEIS BTW ? :)...much vegetation etc. game-engines.
Enable transparency AA and see all those trees, grass etc. without jaggies.
imaheadcase - Thursday, November 9, 2006 - link
Well lots of people don't are for AA. Even if i had this card I would not use it. I visually see NO difference with it on or off. Its personal test. I don't even see "jaggies" on my older 9700 PRO card.flexy - Thursday, November 9, 2006 - link
you sure are talking about ANTIALIASING ???What resoltions do you run ? Not that my CRT can even handle more than 1600x1200..but even w/ 1600 i get VERY prominent jaggies if i dont run AA.
I made it a habit to run at least 4xAA in ANY game, and some engines (hl2:source engine) etc. run extremely well with 4xAA, even 6xAA is very playable at elast with HL2.
The very recent games, namely NWN2 and G3 now dont support AA, playing at 1280x1024 and it looks utterly horrible ! If you say you dont see jags in say ANY resolution under 1600..very hard to believe
imaheadcase - Thursday, November 9, 2006 - link
Yes im talking about antialiasing. I normally play BF2 and oblivion at 1024x768 (9700 pro remember).Fact is most people won't see them unless someone points them out. The brain is still better at rendering stuff the way you want to see it vs hardware :)
flexy - Thursday, November 9, 2006 - link
ok..but then it's also a performance problem. If it doesn't bother you, well ok.I also have to settle w/ the fact that many RECENT games are even unable to do AA..however i wish they would.
But once i get a 8800 i will do &&&& to get the most out of IQ, AA, AF, transparency/texture AF, you name it. ALONE also for the reason that i would need a super-high end monitor first to even run resolutions like 2000xsomething...and as long as i have a lame 19" CRT and CANNOT even go over 1600 (99,99% of games even running everything on 1280x or 1360x) i will use all the power to get out best possible IQ in those low resolutions.
Also..looking at the benchmarks..its NOT that you lose any real time gaming-experiencee since THOSE monster cards are made for exactly this...eg. running oblivion with all those settings at MAX AND AA on and HDR...and you are still in VERY reasobale FPS ranges.