Now let’s estimate the quality of anisotropic filtering by NVIDIA GeForce FX 5900 Ultra compared with that by ATI RADEON 9800 Pro. Again we will use Serious Sam: The Second Encounter:
The game uses OpenGL API, tri-linear filtering is enabled, standard GFX: Extreme Quality settings are used. The only exception here was the anisotropic filtering mode, which we set manually for both graphics cards.
NVIDIA GeForce FX 5900 Ultra was tested with 8x anisotropic filtering in Quality, Balanced and Performance modes. ATI RADEON 9800 Pro was tested with 8x anisotropic filtering in Quality mode. The screenshots with highlighted MIP-levels are also provided for a more illustrative analysis.
In Balanced and Performance modes NVIDIA GeForce FX 5900 Ultra has clearly visible MIP-levels borders, which we surely do not see in Quality mode. However, even in Quality mode NVIDIA GeForce FX 5900 Ultra provides less clear-cut images than ATI RADEON 9800 Pro.
Have you noticed the “dirty” colors of the highlighted MIP-levels by NVIDIA GeForce FX 5900 Ultra? Where do they come from?
These “dirty” colors were formed by two differently highlighted MIP-levels. Despite our expectations, the “stone” surface, which we used to study the image quality, is formed by two textures: the base “stone” texture and one more texture with much lower level of detail adding some bright spots to the pavement, which prevents the surface from looking monotonous from a bigger distance.
It looks as if NVIDIA GeForce FX 5900 Ultra were using a different anisotropic filtering mode for this particular texture, so that MIP-level of the two textures do not coincide and in case of highlighted MIP-levels they overlap thus creating mixed colors.
Well, it does make sense to set lower level of anisotropy or to disable anisotropic filtering at all for such a stretched and inexpressive brightness texture, because ti will increase the performance without any quality losses.
What does the whole thing mean? It indicates that a new optimization method appeared since the times of NVIDIA GeForce4 and anisotropic filtering optimization based on geometric data analysis, which was know as polygon-wise determination. The new method is referred to as texture-wise determination.
When the texture is loaded, the driver must analyze its clearness and set the maximum anisotropy level for the texture depending on the results of this analysis. Moreover, Quality, Balanced and Performance modes use different levels of simplification.
This angle of inclination is very inconvenient for anisotropic filtering algorithms of ATI RADEON 9800 Pro, so that the new ATI solution shows even worse quality than NVIDIA GeForce FX 5900 Ultra in Performance mode.
Here ATI RADEON 9800 Pro and NVIDIA GeForce FX 5900 Ultra in Quality mode show almost the same results.