When we did our last high-end graphics card review, we decided to add some results in MSAA 8x mode, so as to put the power of the most recent monsters at the service of resolution quality. We rapidly noted a problem with Nvidia cards in this mode however.
After some checks we found that when anisotropic filtering is forced via the control panel, MSAA 8x is affected by a modification in the position of samples giving MSAA 2x quality at the cost of 8x. We reported the bug to Nvidia, who were able to reproduce our results but it still hasn’t been corrected. It has been on all pilot revisions for the last few months but we didn’t go back more than a few months so we don’t know exactly how long the bug has been present and we haven’t looked at it again since the mode appeared with the GeForce 8800.
Here is the quality in Oblivion:
From left to right: 4x antialiasing (MSAA 4x) with 16x anisotropic filtering activated in the driver control panel, 8xQ antialiasing (MSAA 8x) without anisotropic filtering and 8xQ antialiasing (MSAA 8x) with 16x anisotropic filtering activated in the driver control panel.As you can see, 8xQ antialiasing gives pretty poor quality as soon as anisotropic filtering is activated in the drivers. There isn’t any link between the filters and the bug is likely simply to be in the drivers. If anisotropic filtering is activated directly in the game, the problem doesn’t appear but, however, it doesn’t make any difference whether antialiasing is activated via the control panel or the game.
By observing the position of the samples with DX9FSAAViewer, we were able to get confirmation:
From left to right: 4x antialiasing (MSAA 4x) with 16x anisotropic filtering activated in the driver control panel, 8xQ antialiasing (MSAA 8x) without anisotropic filtering and 8xQ antialiasing 8xQ (MSAA 8x) with 16xQ anisotropic filtering activated in the driver control panel.The problem appears as soon as anisotropic filtering is activated via the control panel, 8x moving down to 4x mode with an all but satisfactory position of samples which brings antialiasing quality down to something resembling 2x.
We were able to verify that there was no impact on performance however. The validity of the various bench data is therefore borne out. Lets hope that Nvidia sorts the problem out asap. In the meantime we’re left with an important question. Do you people really use the 8x mode? No one picked up on this rather obvious bug and we’ve been wondering if this mode really is used by gamers and whether the testers who do use it actually look at their screens …
