Performance: Anisotropic Filtering and Full-Screen Anti-Aliasing: Speed and Quality

As for anisotropic filtering, NV31 and NV34 perform absolutely the same as their predecessor, NV30. that is why I will not provide any screenshots and performance drop measurements here. If you are looking for more information on that, please, see our NVIDIA GeForce FX 5800 Ultra Review.

The FSAA modes by NVIDIA GeForce FX 5600 Ultra are the same as those of GeForce FX 5800 Ultra, so there are no surprises here, too.

The most exciting things start happening when we turn to NVIDIA GeForce FX 5200/5200 Ultra. Just like GeForce4 chips, they support FSAA 2x, Quincunx and 4x with the help of multisampling. Besides that, you can also get 4xS in Direct3D, which is a combination of supersampling and multisampling. The chips ensure adequate anti-aliasing quality in Application mode, but as soon as you shift to Quality or Performance mode, the picture quality in OpenGL games gets significantly worse. The worsening is represented by slight trembling of the polygon edges if the polygons are close to horizontal. This trembling effect becomes even more noticeably when the resolution gets lower: 1024x768, 800x600, 640x480.

Having analyzed the image quality, we can conclude that in OpenGL with 4s FSAA enabled in Quality and Performance modes NVIDIA GeForce FX 5200/5200 Ultra uses only two subpixels instead of four to calculate the pixel color. Moreover, in case of an even frame two upper subpixels are taken from the 2x2 block, while in case of odd frames – two lower subpixels. This is exactly where this unpleasant lines trembling effect comes from. However in high resolutions with high refresh rate or in case of an LCD monitor with high inertia, this trembling is hardly noticeable. So, even though 2s anti-aliasing is involved, you get the impression that there is fully-fledged anti-aliasing based on 4 subpixels.

It is remarkable that when you run the applications in windows, the real 4x method is applied. But when you take a screenshot the picture again looks as if the true 4x anti-aliasing were used. That is why I failed to take any screenshots proving my point, so I suggest that you take a quick look at a self-made reconstruction with the help of an animated picture:

And below you can see a picture with real 4x anti-aliasing:

Of all graphics cards based on new NVIDIA chips only GeForce FX 5600 Ultra doesn’t have this 4x anti-aliasing optimization. All other graphics cards including NVIDIA GeForce FX 5200/5200 Ultra, GeForce4 Ti4200-8x, GeForce4 MX440-8x demonstrated the work of an “optimized” 4x anti-aliasing algorithm with 43.45 driver. As I have already said, this annoying trembling can be best seen in low resolutions. Moreover, by GeForce4 MX440-8x these are not only the polygon edges that tremble, but the entire image.

This optimization has the right to exist and is absolutely justified: during our test session we discovered that it worked on those cards, which didn’t support frame buffer compression during full-screen anti-aliasing. But why did they call the mode when this optimization gets activated, “Quality”? it would be much more logical to call Quality the current Application mode, where the cards do honestly perform 4x full-screen anti-aliasing.

Well, let’s now estimate the performance difference shown by graphics cards in different quality modes. We will use Quake3 Arena game:

Without FSAA and anisotropic filtering, the performance difference in various quality modes is not that big...

But as soon as we enable full-screen anti-aliasing, the performance difference starts growing. You can clearly see how greatly the performance dropped in Application mode enabled by NVIDIA GeForce FX 5200 Ultra: the chip has to perform true 4x full-screen anti-aliasing.

With anisotropic filtering enabled, the performance difference also grows bigger. The Application mode appears the hardest for all chips, because there they have to perform true tri-linear filtering instead of a mixture with bi-linear filtering.

In the hardest testing conditions with enabled anisotropic filtering and full-screen anti-aliasing, the graphics cards in Application mode appear up to 30-40% slower than they were in Performance mode.

So, if we take into account the quality and fastness of anisotropic filtering and full-screen anti-aliasing, we can say that new NVIDIA chips show practically the same results as NVIDIA GeForce FX 5800 Ultra.

We can once again praise the new NV31/NV34 chips for the same anisotropic filtering method as by NV30, which ensure high image quality at the expense of pretty low performance losses.

As for FSAA, things are not so smooth here. The brand new “optimization “ of the 4x method may discourage you so greatly in OpenGL applications that you will never use the Quality mode again. Especially, since in the Application mode, the cards still run acceptably fast due to well-implemented multisampling support.