Texture Filtering Image Quality

Texture filtering is always a hot topic when a new GPU is introduced. For the past few years, every new architecture has had a new take on where and how to optimize texture filtering. The community is also very polarized and people can get really fired up about how this company or that is performing an optimization that degrades the user's experience.

The problem is that all 3D graphics is an optimization problem. If GPUs were built to render every detail of every of every scene without any optimization, rather than frames per second, we would be looking at seconds per frame. Despite this, looking at the highest quality texture filtering available is a great place from which to start working our way down to what most people will use.

The good news is that G80 completely eliminates angle dependent anisotropic filtering. Finally we have a return to GeForce FX quality anisotropic filtering. When stacked up against R580 High Quality AF with no optimizations enabled on either side (High Quality mode for NVIDIA, Catalyst AI Disabled for ATI), G80 definitely shines. We can see at 8xAF (left) under NVIDIA's new architecture is able to more accurately filter textures based on distance from and angle to the viewer. On the right, we see ATI's angle independent 16xAF degrade in quality to a point where different texture stages start bleeding into one another in undesirable ways.



ATI G80

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Oddly enough, ATI's 16xAF is more likely to cause shimmering with the High Quality AF box checked than without. Even when looking at an object like a flat floor, we can see the issue pop up in the D3DAFTester. NVIDIA has been battling shimmering issues due to some of their optimizations over the past year or so, but these issues could be avoided through driver settings. There isn't really a way to "fix" ATI's 16x high quality AF issue.



ATI Normal Quality AF ATI High Quality AF

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But, we would rather have angle independent AF than not, so for the rest of this review, we will enable High Quality AF on ATI hardware. This will give us a more fair comparison to G80, even if we still aren't really looking at two bowls of apples. G70 is not able to enable angle independent AF, so we'll be stuck with the rose pattern we've been so familiar with over the past few years.

There is still the question of how much impact optimization has on texture filtering. With G70, disabling optimizations resulted in more trilinear filtering being done, and thus a potential performance decrease. The visual result is minimal in most cases, as trilinear filtering is only really necessary to blur the transition between mipmap levels on a surface.



G70 Normal Quality AF G70 High Quality AF

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On G80, we see a similar effect when comparing default quality to high quality. Of course, with angle independent anisotropic, we will have to worry less about shimmering period, so optimizations shouldn't cause any issues here. Default quality does show a difference in the amount of trilinear filtering being applied, but this does not negatively impact visual quality in practice.



G80 Normal Quality AF G80 High Quality AF

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What's Transparency AA? Turning Optimizations Off
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  • haris - Thursday, November 9, 2006 - link

    You must have missed the article they published the very next day http://www.theinquirer.net/default.aspx?article=35...">here. saying they goofed. Reply
  • Araemo - Thursday, November 9, 2006 - link

    Yes I did - thanks.

    I wish they would have updated the original post to note the mistake, as it is still easily accessible via google. ;) (And the 'we goofed' post is only shown when you drill down for more results)
    Reply
  • Araemo - Thursday, November 9, 2006 - link

    In all the AA comparison photos of the power lines, with the dome in the background - why does the dome look washed out in the G80 images? Is that a driver glitch? I'm only on page 12, so if you explain it after that.. well, I'll get it eventually.. ;) But is that just a driver glitch, or is it an IQ problem with the G80 implementation of AA? Reply
  • bobsmith1492 - Thursday, November 9, 2006 - link

    Gamma-correcting AA sucks. Reply
  • Araemo - Thursday, November 9, 2006 - link

    That glitch still exists whether or not gamma-correcting AA is enabled or disabled, so that isn't it. Reply
  • iwodo - Thursday, November 9, 2006 - link

    I want to know if these power hungry monster have any power saving features?
    I mean what happen if i am using Windows only most of the time? Afterall CPU have much better power management when they are idle or doing little work. Will i have to pay extra electricity bill simply becoz i am a cascual gamer with a power - hungry/ ful GPU ?

    Another question pop up my mind was with CUDA would it now be possible for thrid party to program a H.264 Decoder running on GPU? Sounds good to me:D
    Reply
  • DerekWilson - Thursday, November 9, 2006 - link

    oh man ... I can't believe I didn't think about that ... video decoder would be very cool. Reply
  • Pirks - Friday, November 10, 2006 - link

    decoder is not interesting, but the mpeg4 asp/avc ENCODER on the G80 GPU... man I can't imagine AVC or ASP encoding IN REAL TIME... wow, just wooowww
    I'm holding my breath here
    Reply
  • Igi - Thursday, November 9, 2006 - link

    Great article. The only thing I would like to see in a follow up article is performance comparison in CAD/CAM applications (Solidworks, ProEngineer,...).

    BTW, how noisy are new cards in comparison to 7900GTX and others (in idle and under load)?
    Reply
  • JarredWalton - Thursday, November 9, 2006 - link

    I thought it was stated somewhere that they are as loud (or quiet if you prefer) as the 7900 GTX. So really not bad at all, considering the performance offered. Reply

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