NVIDIA Anti-Aliasing, Linux & Lenvik
Recently via email we were asked to run a comparison of the different anti-aliasing and image rendering options between the ATI/AMD and NVIDIA Linux drivers and hardware. Well, we have now run a few quantitative and qualitative tests at different anti-aliasing levels under Linux. For those that want to run the tests themselves with their own drivers and hardware, we also have provided instructions on how you can easily do so using the Phoronix Test Suite 2.4 "Lenvik" development build -- it is irresistibly easy.
For this round of quick testing we were using an Intel Core 2 Duo E8400 processor clocked at 3.86GHz and then on the graphics side was a GeForce 8600GTS 256MB graphics card. We were running Ubuntu Linux with the NVIDIA 195.22 display driver, which is currently in beta. We had ran our set of tests using no anti-aliasing, 4x anti-aliasing using multi-sampling, 8x AA using 4x multi-sampling anti-aliasing and 4x coverage sample anti-aliasing, and then 16x AA using 8x MSAA and 8x CSAA. To start with, below are the average frame-rates for this NVIDIA setup at the different AA levels. This testing was all done using a Git version of Phoronix Test Suite 2.4. The graph below and then the Nexuiz image quality tests were all done by simply running phoronix-test-suite benchmark nexuiz nexuiz-iqc at each of the anti-aliasing levels that were overridden by the NVIDIA Linux driver and we let our software take care of the rest. The Phoronix Test Suite does output these image quality comparison screenshots as uncompressed PNG files, however, for bandwidth concerns on Phoronix.com we have compressed these PNG files using The GIMP.
When maxing out the anti-aliasing capabilities for this driver and GeForce 8600GTS, the frame-rate had dropped by more than 40% when running at 1280 x 1024. The biggest performance drop had occurred between running with no AA and then when using 4x MSAA. There was a very small performance drop between 4x MSAA and 4x MSAA, 4x CSAA, while the performance drop had amplified when switching from 8x AA to 16x. Even running with 8x MSAA and 8x CSAA, Nexuiz was still very much playable at this resolution and with a NVIDIA graphics card that is now considered low-end by today's standards.
To answer how the image quality is impacted at each of these AA levels, there is the nexuiz-iqc test profile that tells us by capturing screenshots automatically through the Phoronix Test Suite with frame accuracy. This allows the Phoronix Test Suite to go beyond just measuring frame rates and is a new feature for 2.4 Lenvik. Below is the weapon rendering scene from Nexuiz, take note of the edges around the weapon where there are slightly less jaggies at the higher AA levels.
Below is an explosion scene from Nexuiz, but to look for AA differences, in particular note the shoulders of the opponent in each of the different screenshots.
Having problems seeing any of the differences? The Phoronix Test Suite can help you there too. After running an image quality comparison, simply run phoronix-test-suite analyze-image-delta <saved name>, which will then prompt you to select a base image and comparison image and then will render those two images along with a third "delta" image that clearly highlights areas of the composite screenshot where there are differences between the two images that exceed a defined threshold. Below is a sample showing off the explosion scene after running phoronix-test-suite analyze-image-delta nvidia-aa with no AA and then 8x MSAA / 8x CSAA.