Product: AMD Catalyst
Company: AMD
Authour: James Prior
Editor: Charles Oliver
Date: December 13th, 2010
Part II - Image Quality Investigation

Rage3D
Rage3D
When AMD launched the new HD 6000 series in October, some of the Barts architecture details generated a large amount of interest. AMD implemented some changes to improve their visual fidelity, specifically regarding Anisotropic Filtering. At the introduction of the codename Cypress based HD 5800 series, AMD touted their improvements in Anisotropic Filtering by implementing an angle independent filter. This meant that no matter the angle of view from the plane of the surface to which the texture was applied, the filtering would be same and thus more representative of the desired image.


Investigations into this was initially limited to reproducing the 'AF Flower' which showed the angle filtering level being consistent - no spikes, or squares, just a nice smooth circle. AMD was pleased with their new angle-independent filtering, something that Nvidia has yet to match even on their latest generation hardware. However, as time passed by, a problem was found in another aspect of texturing; kernel transitions. The problem noted on AMD's HD 5000 series was that sometimes the transition (change from one filtering level to the next) wasn't quite as smooth as it should be. While the angle independence improved filtered texture image quality, the kernel transition detracted from it in certain circumstances. This could cause banding, an obvious difference in color in the same texture which in motion was sometimes perceptible as texture corruption. When applying a texture to a surface, the same size and quality image isn't always used for all distances from the viewpoint.

The 'AF' Flower
The 'AF' Flower

Having isolated the issue, AMD implemented a fix in the HD 6800 Barts series graphics cards, thus improving the transition from one mipmap to the next while retaining the angle independent filtering. Things were looking good, and AMD was once again pleased with their efforts. However, a second texture filtering problem became prominent, based on shimmering observed in a pathological-worst-case benchmark tester tool: 3DCenter.org's Filter Tester. Despite the angle independence, and the improved transitions, a shimmer is seen in the tool when observing a moving noisy texture.

Highlighting 'Shimmer' Areas
Highlighting 'Shimmer' Areas

Radeon
Radeon
As part of the new driver released for the HD 6800, there were some changes to the image quality options available. Gone were the Narrow and Wide Tent MSAA modes, leaving only the standard Xox and excellent, but performance sapping, Edge Detect MSAA modes. Changes to the Catalyst Application Intelligence (AI) slider appeared as well, with a new Texture Quality slider replacing Cat AI standard or advanced. The new default settings for Texture Quality is Quality, which is not the highest quality mode - there are some optimizations performed, that AMD states shouldn't visibly affect image quality but can increase performance.


HD 6000 Default Quality Setting
HD 6000 Default Quality Setting


Setting the slider to High Quality disables all optimizations, as with previously disabling Cat AI. However, disabling Cat AI prevented Crossfire and other important driver features (driver profile aspects unrelated to image quality) from being active. The new setting allows application profiles and Crossfire to still work, but removes all image quality optimizations. This sounds contradictory, but relies on differentiating between texture and quality optimizations and application settings for performance that don't affect quality.

HD 5000 Catalyst 10.10 Default Quality Setting
HD 5000 Catalyst 10.10 Default Quality Setting

By its very nature, filtering alters the source data - the image. PC gamers can typically be loosely divided into three groups - Image Quality Enthusiasts, Performance Enthusiasts, and Everybody Else. The Everybody Else crowd is the largest, and they can't quite understand why the other two groups are running around like their hair is on fire, yelling about blobby pixels on a computer screen; they wish they'd stop and let everyone enjoy the quiet life. However, they can appreciate good visuals and solid performance.

Rage3D
Rage3D
The second purpose of today's article is to look at the default and enhanced image quality offered by AMD and Nvidia, investigating a couple of issues that have been brought to prominence recently. We'll also look a little at the different image quality options available from both vendors, and see if a 'best effort' better than MSAA image quality and performance comparison is possible. 


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