Image Quality
I can't do much on image quality due to time contraints, but here's an example of D3D mip level texture filtering on both ATI and NVIDIA boards, using D3D, in Serious Sam 2. I chose the technology test level, applied user set 4xAA and 8xAF and used a long view up one of the shadowed pathways.What you are looking for is obvious stepped banding between the textures on the floor, as the view goes away from you. If the texture stages don't blend together well, you'll notice it, indicating a poor quality trilinear filter.
Here are the images side by side, 52.16 on FX5950 first, CAT3.6 on 9800XT second. Both shots are saved with level 10 JPEG compression, click on the images for the original .tga's (300kb+ each).
Notice how it seems to gradiate smoothly off into the distance in the NVIDIA card shot, despite a poorer trilinear filter?
If there's an obvious difference between the two floor textures, I can't see it. The wall and roof textures have more texture detail in the ATI shot, alluding to the higher quality trilinear being visible there. The ATI shot has more obvious texture detail, but the floor texture trilinear on the NVIDIA shot (the most obvious place to look for it, and what I'm concentrating on), doesn't appear too bad.
It seems to suggest that despite a poorer trilinear filter, just how poor is it compared to the 'correct' one? I'm not afraid to say I really struggle to see a difference, while playing games. Analysing a static screenshot is a different beast to watching a moving picture.
Here's another couple of shots from each card, UT2003 this time, to highlight aniso quality and texture filtering.
UT2003 Antalus ground texture, ATI Radeon 9600XT
UT2003 Antalus ground texture, FX 5700 Ultra
In those shots, I can see mip filtering between stages on both cards, with no apparent difference in aniso quality. I know it's there, UT2003 is running in D3D mode and I know the driver is broken doing trilinear with D3D, but I can't see it.
I'll finish off my proper 52.16 IQ analysis if and when time permits. Looking at texture detail from one game isn't indicative of overall image quality, although it can help identify problems. The ATI boards appear to look better, but just how much better is hard to say. Personally, I have no real complaints with NVIDIA IQ while playing a range of games recently (and even less complaints playing on ATI hardware).
