![[H]ardOCP](/images/blank.gif){kind=small}
- Date:
- Sunday , July 20, 2008
- Author:
- Brent Justice
- Editor:
- Kyle Bennett
- Google +1
AMD's ATI Radeon HD 4800 Series Custom Filtering AA
AMD’s new ATI Radeon HD 4800 series provides shader powered antialiasing features! We examine in-game IQ and AA scaling. We’ve got all the information on using the Edge-detect Custom Filtering AA and what it will do for you in-game. If you are not sure how to best leverage your new 4870 or 4850 video cards, we show you how.
AA Image Quality Comparisons
Here we are going to evaluate image quality of the available antialiasing modes present with the Radeon HD 4800 series. We are going to see how 2X AA compares to 4X AA compares to 8X AA compares to 12X CFAA compares to 24X CFAA and then with Adaptive AA enabled.
This page is nothing but screenshot comparisons, and some are quite large in file size. Take note that each one is saved in PNG format and the largest on this page is 2.2 MB. Also, we are going to show you the normal view size of the image (100% normal view) plus an enlarged zoomed in image at 200% for those that like to take a closer look at the AA sample patterns. Due to enlarging the comparisons to 200% there are some quite physically large screenshots here, the largest on this page is 1872x3024 in resolution.
The acronyms used on this page are broken down as such:
CF AA = Custom Filtering Edge-detect filter
AD AA = Adaptive Antialiasing at the Supersampling Quality level
The first screenshot on the left will be the normal view, the right will be the zoomed in 200% view.
We are using three games for looking at AA image quality due to the ability to use “identical” saved game camera placements. These games contain brightly lit areas that make aliasing easy to spot. We will be using Half Life 2, Half Life 2 Episode 2, and Crysis. Each game is set at 1280x1024 with the highest in-game settings. In the case of Crysis we are running the game in DX9 mode so that we can use CFAA, and are running that game at all “High” settings.
All AA Levels Compared
For this first round of image quality screenshots we are looking at all modes on the Radeon HD 4870 compared, 2X AA, 4X AA, 8X AA, 12X CFAA and 24X CFAA.
In Half Life 2 and Episode 2 it becomes quite clear when looking at the benefits AA provides. When looking at the first image above, of the power lines, we see a clear progression of benefits with AA enabled. Looking so very closely at the power lines above what we notice is that 12X CFAA isn’t quite as good as 8X AA to our eyes. It is better than 4X AA for sure, but maybe slightly below 8X AA. When you look at the zoomed in screenshot of the power lines you can easily see this. Looking at 24X CFAA though clearly shows a better image quality than 8X AA.
In the rest of the screenshots 12X CFAA looks rather similar to 8X MSAA, some might argue it is better, others will argue it looks the same. What is great about it is that it has similar IQ to 8X MSAA, but at the memory cost of 4X AA.
Now we can take a look at Crysis. The first thing you will notice is that the image with NoAA looks a bit blurry, this is actually what it looked like in-game without AA. It also looked exactly like this with AMD & NVIDIA hardware. Enabling AA actually improved the image quality and made the “blurry” go away in the game on both ATI and NVIDIA hardware. This blurriness seems to be a game dependent issue when AA is not enabled, using all “High” settings in DX9 mode. We haven’t experienced this in DX10 mode, which is the mode we have been testing for quite some time now.
In all of these screenshots, again, image quality gets progressively better. It can be argued whether 12X CFAA is better or the same as 8X MSAA once again. If you look at the zoomed in shot of the crane you can see some areas where 12X CFAA does have a smoother gradient, the problem is it is hard to see the difference at normal view.
Adaptive AA Compared
Now it is time to look at image quality with Adaptive AA enabled. For these shots we are using Half Life 2 and Half Life 2 Episode 2 at 1280x1024 with the highest in-game settings. Crysis does not support any form of transparency AA on either ATI or NVIDIA hardware, it is a game issue.
Adaptive AA is clearly working and providing image quality improvements along with CFAA. Notice though what we were talking about in the introduction, 12X CF AD AA actually has the same Adaptive AA quality as 4X AD AA does. This makes sense because we are still at 4X MSAA with CF AA enabled, so the alpha texture is still receiving 4X samples here apparently. When we enable 24X CF AD AA we now have 8X MSAA selected, and the image quality matches that of the 8X AD AA screenshot.