AMD's Radeon HD 5870: Bringing About the Next Generation Of GPUs
by Ryan Smith on September 23, 2009 9:00 AM EST- Posted in
- GPUs
The Return of Supersample AA
Over the years, the methods used to implement anti-aliasing on video cards have bounced back and forth. The earliest generation of cards such as the 3Dfx Voodoo 4/5 and ATI and NVIDIA’s DirectX 7 parts implemented supersampling, which involved rendering a scene at a higher resolution and scaling it down for display. Using supersampling did a great job of removing aliasing while also slightly improving the overall quality of the image due to the fact that it was sampled at a higher resolution.
But supersampling was expensive, particularly on those early cards. So the next generation implemented multisampling, which instead of rendering a scene at a higher resolution, rendered it at the desired resolution and then sampled polygon edges to find and remove aliasing. The overall quality wasn’t quite as good as supersampling, but it was much faster, with that gap increasing as MSAA implementations became more refined.
Lately we have seen a slow bounce back to the other direction, as MSAA’s imperfections became more noticeable and in need of correction. Here supersampling saw a limited reintroduction, with AMD and NVIDIA using it on certain parts of a frame as part of their Adaptive Anti-Aliasing(AAA) and Supersample Transparency Anti-Aliasing(SSTr) schemes respectively. Here SSAA would be used to smooth out semi-transparent textures, where the textures themselves were the aliasing artifact and MSAA could not work on them since they were not a polygon. This still didn’t completely resolve MSAA’s shortcomings compared to SSAA, but it solved the transparent texture problem. With these technologies the difference between MSAA and SSAA were reduced to MSAA being unable to anti-alias shader output, and MSAA not having the advantages of sampling textures at a higher resolution.
With the 5800 series, things have finally come full circle for AMD. Based upon their SSAA implementation for Adaptive Anti-Aliasing, they have re-implemented SSAA as a full screen anti-aliasing mode. Now gamers can once again access the higher quality anti-aliasing offered by a pure SSAA mode, instead of being limited to the best of what MSAA + AAA could do.
Ultimately the inclusion of this feature on the 5870 comes down to two matters: the card has lots and lots of processing power to throw around, and shader aliasing was the last obstacle that MSAA + AAA could not solve. With the reintroduction of SSAA, AMD is not dropping or downplaying their existing MSAA modes; rather it’s offered as another option, particularly one geared towards use on older games.
“Older games” is an important keyword here, as there is a catch to AMD’s SSAA implementation: It only works under OpenGL and DirectX9. As we found out in our testing and after much head-scratching, it does not work on DX10 or DX11 games. Attempting to utilize it there will result in the game switching to MSAA.
When we asked AMD about this, they cited the fact that DX10 and later give developers much greater control over anti-aliasing patterns, and that using SSAA with these controls may create incompatibility problems. Furthermore the games that can best run with SSAA enabled from a performance standpoint are older titles, making the use of SSAA a more reasonable choice with older games as opposed to newer games. We’re told that AMD will “continue to investigate” implementing a proper version of SSAA for DX10+, but it’s not something we’re expecting any time soon.
Unfortunately, in our testing of AMD’s SSAA mode, there are clearly a few kinks to work out. Our first AA image quality test was going to be the railroad bridge at the beginning of Half Life 2: Episode 2. That scene is full of aliased metal bars, cars, and trees. However as we’re going to lay out in this screenshot, while AMD’s SSAA mode eliminated the aliasing, it also gave the entire image a smooth makeover – too smooth. SSAA isn’t supposed to blur things, it’s only supposed to make things smoother by removing all aliasing in geometry, shaders, and textures alike.
As it turns out this is a freshly discovered bug in their SSAA implementation that affects newer Source-engine games. Presumably we’d see something similar in the rest of The Orange Box, and possibly other HL2 games. This is an unfortunate engine to have a bug in, since Source-engine games tend to be heavily CPU limited anyhow, making them perfect candidates for SSAA. AMD is hoping to have a fix out for this bug soon.
“But wait!” you say. “Doesn’t NVIDIA have SSAA modes too? How would those do?” And indeed you would be right. While NVIDIA dropped official support for SSAA a number of years ago, it has remained as an unofficial feature that can be enabled in Direct3D games, using tools such as nHancer to set the AA mode.
Unfortunately NVIDIA’s SSAA mode isn’t even in the running here, and we’ll show you why.
5870 SSAA
GTX 280 MSAA
GTX 280 SSAA
At the top we have the view from DX9 FSAA Viewer of ATI’s 4x SSAA mode. Notice that it’s a rotated grid with 4 geometry samples (red) and 4 texture samples. Below that we have NVIDIA’s 4x MSAA mode, a rotated grid with 4 geometry samples and a single texture sample. Finally we have NVIDIA’s 4x SSAA mode, an ordered grid with 4 geometry samples and 4 texture samples. For reasons that we won’t get delve into, rotated grids are a better grid layout from a quality standpoint than ordered grids. This is why early implementations of AA using ordered grids were dropped for rotated grids, and is why no one uses ordered grids these days for MSAA.
Furthermore, when actually using NVIDIA's SSAA mode, we ran into some definite quality issues with HL2: Ep2. We're not sure if these are related to the use of an ordered grid or not, but it's a possibility we can't ignore.
If you compare the two shots, with MSAA 4x the scene is almost perfectly anti-aliased, except for some trouble along the bottom/side edge of the railcar. If we switch to SSAA 4x that aliasing is solved, but we have a new problem: all of a sudden a number of fine tree branches have gone missing. While MSAA properly anti-aliased them, SSAA anti-aliased them right out of existence.
For this reason we will not be taking a look at NVIDIA’s SSAA modes. Besides the fact that they’re unofficial in the first place, the use of a rotated grid and the problems in HL2 cement the fact that they’re not suitable for general use.
Facebook
Twitter
RSS
327 Comments
View All Comments
ClownPuncher - Wednesday, September 23, 2009 - link
Absolutely, I can answer that for you.Those 2 "ports" you see are for aesthetic purposes only, the card has a shroud internally so those 2 ports neither intake nor exhaust any air, hot or otherwise.
Ryan Smith - Wednesday, September 23, 2009 - link
ClownPuncher gets a cookie. This is exactly correct; the actual fan shroud is sealed so that air only goes out the front of the card to go outside of the case. The holes do serve a cooling purpose though; allow airflow to help cool the bits of the card that aren't hooked up to the main cooler; various caps and what have you.SiliconDoc - Wednesday, September 23, 2009 - link
Ok good, now we know.So the problem now moves to the tiny 1/2 exhaust port on the back, did you stick your hand there and see how much that is blowing ? Does it whistle through there ? lol
Same amount of air(or a bit less) in half the exit space... that's going to strain the fan and or/reduce flow, no matter what anyone claims to the contrary.
It sure looks like ATI is doing a big favor to aftermarket cooler vendors.
GhandiInstinct - Wednesday, September 23, 2009 - link
Ryan,Developers arent pushing graphics anymore. Its not economnical, PC game supports is slowing down, everything is console now which is DX9. what purpose does this ATI serve with DX11 and all this other technology that won't even make use of games 2 years from now?
Waste of money..
ClownPuncher - Wednesday, September 23, 2009 - link
Clearly he should stop reviewing computer technology like this because people like you are content with gaming on their Wii and iPhone.This message has been brought to you by Sarcasm.
Griswold - Wednesday, September 23, 2009 - link
So you're echoing what nvidia recently said, when they claimed dx11/gaming on the PC isnt all that (anymore)? I guess nvidia can close shop (at least the gaming relevant part of it) now and focus on GPGPU. Why wait for GT300 as a gamer?Oh right, its gonna be blasting past the 5xxx and suddenly dx11 will be the holy grail again... I see how it is.
SiliconDoc - Wednesday, September 23, 2009 - link
rofl- It's great to see red roosters not crowing and hopping around flapping their wings and screaming nvidia is going down.Don't take any of this personal except the compliments, you're doing a fine job.
It's nice to see you doing my usual job, albiet from the other side, so allow me to compliment your fine perceptions. Sweltering smart.
But, now, let's not forget how ambient occlusion got poo-pooed here and shading in the game was said to be "an irritant" when Nvidia cards rendered it with just driver changes for the hardware. lol
Then of course we heard endless crowing about "tesselation" for ati.
Now it's what, SSAA (rebirthed), and Eyefinity, and we'll hear how great it is for some time to come. Let's not forget the endless screeching about how terrible and useless PhysX is by Nvidia, but boy when "open standards" finally gets "Havok and Ati" cranking away, wow the sky is the limit for in game destruction and water movement and shooting and bouncing, and on and on....
Of course it was "Nvidia's fault" that "open havok" didn't happen.
I'm wondering if 30" top resolution will now be "all there is!" for the next month or two until Nvidia comes out with their next generation - because that was quite a trick switching from top rez 30" DOWN to 1920x when Nvidia put out their 2560x GTX275 driver and it whomped Ati's card at 30" 2560x, but switched places at 1920x, which was then of course "the winning rez" since Ati was stuck there.
I could go on but you're probably fuming already and will just make an insult back so let the spam posting IZ2000 or whatever it's name will be this time handle it.
BTW there's a load of bias in the article and I'll be glad to point it out in another post, but the reason the red rooster rooting is not going beyond any sane notion of "truthful" or even truthiness, is because this 5870 Ati card is already percieved as " EPIC FAIL" !
I cannot imagine this is all Ati has, and if it is they are in deep trouble I believe.
I suspect some further releases with more power soon.
Finally - Wednesday, September 23, 2009 - link
Team Green - full foam ahead!*hands over towel*
There you go. Keep on foaming, I'm all amused :)
araczynski - Wednesday, September 23, 2009 - link
is DirectX11 going to be as worthless as 10? in terms of being used in any meaningful way in a meaningful amount of games?my 2 4850's are still keeping me very happy in my 'ancient' E8500.
curious to see how this compares to whatever nvidia rolls out, probably more of the same, better in some, worse in others, bottom line will be the price.... maybe in a year or two i'll build a new system.
of course by that time these'll be worthless too.
SiliconDoc - Wednesday, September 23, 2009 - link
Well it's certainly going to be less useful than PhysX, which is here said to be worthless, but of course DX11 won't get that kind of dissing, at least not for the next two months or so, before NVidia joins in.Since there's only 1 game "kinda ready" with DX11, I suppose all the hype and heady talk will have to wait until... until... uhh.. the 5870's are actually available and not just listed on the egg and tiger.
Here's something else in the article I found so very heartwarming:
---
" Wrapping things up, one of the last GPGPU projects AMD presented at their press event was a GPU implementation of Bullet Physics, an open source physics simulation library. Although they’ll never admit it, AMD is probably getting tired of being beaten over the head by NVIDIA and PhysX; Bullet Physics is AMD’s proof that they can do physics too. "
---
Unfortunately for this place,one of my friends pointed me to this little expose' that show ATI uses NVIDIA CARDS to develope "Bullet Physics" - ROFLMAO
-
" We have seen a presentation where Nvidia claims that Mr. Erwin Coumans, the creator of Bullet Physics Engine, said that he developed Bullet physics on Geforce cards. The bad thing for ATI is that they are betting on this open standard physics tech as the one that they want to accelerate on their GPUs.
"ATI’s Bullet GPU acceleration via Open CL will work with any compliant drivers, we use NVIDIA Geforce cards for our development and even use code from their OpenCL SDK, they are a great technology partner. “ said Erwin.
This means that Bullet physics is being developed on Nvidia Geforce cards even though ATI is supposed to get driver and hardware acceleration for Bullet Physics."
---
rofl - hahahahahha now that takes the cake!
http://www.fudzilla.com/content/view/15642/34/">http://www.fudzilla.com/content/view/15642/34/
--
Boy do we "hate PhysX" as ati fans, but then again... why not use the nvidia PhysX card to whip up some B Physics, folks I couldn't make this stuff up.