Bugged GeForce Drivers Improve Image Quality

Article Index

Image Quality (Cont): Enter ATI, Performance Impact

We're not talking much about ATI's comparative image quality, but we did grab screenshots of the Red Team's multisampling (DX11) and supersampling (DX9) in the same area. The top two images are ATI's multisampling and supersampling; NVIDIA's 4xSSAA is below.

ATI Multisampling

ATI Supersampling

NVIDIA Supersampling

Comparing the ATI and NVIDIA supersampling methods we see that while the NVIDIA method is blurrier, it's also more effective at eliminating jagged edges. Based on what we know about NVIDIA's supersampling method as forced by nHancer and ATI's historical approach, the different image results from the use of two different pixel sampling methods.

Click to enlarge (left thumbnail)

NVIDIA uses an ordered grid approach, which samples every pixel in an image the same way from the same points. This is less effective on 45' angles or on lines that are nearly (but not quite) perfectly horizontal or vertical. If you want to see an example of the effect, click the left thumbnail above. At certain angles, the human perceives the lines as more or less aliased. In years past, ATI relied on what it calls sparse grid super sampling, claiming that this method was better at handling angled lines. In theory, the ATI images are applying 8x sparse grid compared to NVIDIA's 4x4 ordered grid, but since we're comparing a buggy driver against a game that's been forced to run in DX9 mode for comparison shots, we can't say with 100 percent certainty that the proper modes have been applied.

Performance Impact:
We've focused on 4xSSAA because it's the sweet spot between visual quality and performance; 2x supersampling is available but doesn't improve image quality much. 8xSSAA is also technically available, but produces a very blurred image. In addition, the performance penalty from 8x drives even a pair of GTX 480's in SLI mode to their knees in DX11.

Testbed: Intel Core i7 980X @ 4.2GHz, 6GB DDR3, 2x GTX480's in SLI

Switching from 8x multisampling to 4x supersampling cuts performance by more than half, 8x supersampling cuts the GTX 480's framerate in SLI mode by almost 75 percent. This isn't a veiled shot at the GTX 480's performance; remember that for every pixel displayed, up to eight more are being rendered, textured, and lit. In this case, lowering the detail level or the baseline resolution is the most effective way to solve the problem. Back when display resolutions were much smaller, there were certain enthusiasts who eschewed the use of supersampling-based FSAA in favor of playing at higher resolutions—1600x1200, for example, rather than 800x600 with 4xAA. Nowadays, that's not possible--any baseline resolution above 1280x1024 results in the card internally sampling at resolutions well above 2560x1600.

Related content


Show comments blog comments powered by Disqus