The Future of Anti-Aliasing Settings in Question: NVIDIA Discussionby Derek Wilson on March 15, 2007 8:23 AM EST
- Posted in
The Increasing Complexity of AA
As we mentioned, the first major difficulty with antialiasing is compatibility. Generally the burden is on the game developer to assess the capabilities of the hardware on which it is running and make options available to users based on what is available. Problems arise in that game developers aren't able to look into the future and program for hardware that isn't available. For example, X1000 Series and GeForce 8 Series hardware can run Oblivion with both HDR and AA enabled, but at least GeForce 8 hardware wasn't available when Oblivion launched, so the developers don't test for the capability to antialias floating point surfaces and simply disable the AA option when HDR is enabled.
When games that could benefit from AA on current hardware don't offer the option, we have no choice but to look to the driver for support. Of course, we do have bigger problems on the horizon. Some developers are currently choosing options such as deferred rendering for their games. Current techniques make use of multiple render targets (MRTs) to render objects or effects which are later combined to form a final image. MSAA does not play well with this technique, as one of the basic requirements is knowing what surfaces overlap a single pixel on the screen. Forcing AA on in the driver can cause problems in games where MSAA simply will not work. Current examples of this can be seen in these games:
- Ghost Recon: Advanced Warfighter
- Rainbow Six: Vegas
With the functionality of driver enabled AA dependent on the game being run, graphics hardware makers are not able to guarantee that the user will get the results he or she desires. This means that the driver setting is more like asking the hardware to enable AA if possible. This uncertainty as to the behavior of the feature can cause problems for end users of both AMD and NVIDIA hardware.
As for NVIDIA specifically, its new CSAA (Coverage Sample Antialiasing) technology adds another layer to the complexity of antialiasing settings in the driver. Now, rather than just selecting a desired level of antialiasing, we need to decide to what degree we want to either enhance or override the application. Enhancing only works when AA is enabled in-game as well, and override won't override games that make use of technology that is incompatible with MSAA. While the features function as they should, even some hardcore gamers out there may not know what they are getting when they enable AA in the control panel.
At AnandTech, we have avoided using driver AA settings as much as possible since the initial release of Far Cry which produced inconsistent results between graphics hardware manufacturers when set through their respective control panels. These specific problems were worked out in later driver and game updates, but we find it more effective to rely on the game developer for consistency between common hardware features. Where there is an in-game setting, we use it. For us, other than disabling vsync, driver settings are a last resort.
It is safe to say that AMD and NVIDIA feel the same way. The only way they currently have to inform their users about the lack of support for AA in specific games is though their release notes. No one wants the end user to have a bad experience through glitchy performance.
One of the best ways to make sure gamers stick with in-game settings is to make sure developers offer clearly defined, well documented, and complete settings for features such as AA. In order to better enable this, NVIDIA has been working with Microsoft to enable CSAA through DirectX. With the in-game option for CSAA, users won't have to wade through the driver options and can directly select the type and degree of AA they want applied to their game.
In DirectX 9 and 10, requesting AA on a surface involves determining the level (number of subsamples) of AA and the quality of AA. Most games just set quality to 0, as hardware previous hardware didn't really do anything with this field. The method developers can use to set CSAA in-game is to set the level of AA to either 4 or 8 and then set the quality to 8 or 16 (2 or 4 in DX9, as quality levels are limited to 7 or less). This functionality is exposed in NVIDIA's 100 series driver.
This has had some unwanted side effects though. In the past it hasn't mattered, but some developers would detect the highest quality setting available and select it when enabling AA in-game. These games when paired with NVIDIA's 100 series driver will inadvertently enable 16x CSAA when 4x AA is selected. Currently the games that exhibit this behavior are:
- Battlefield 2
- Battlefield 2142
- Sin Episodes
- Half-Life 2
- Half-Life 2: Lost Coast
- Dark Messiah of Might and Magic
This is only an issue on Vista for now, but 100 series drivers will be coming to XP soon. It isn't that either NVIDIA or these game developers are doing anything wrong, it's just how things ended up working out. The ability to enable CSAA in games does outweigh these minor issues in our minds though. We hope to see this number rise, but currently there are only two games that support enabling CSAA in-game:
- Half-Life 2: Episode 1
- Supreme Commander
So with the 100 series driver, future games will be able to enable all of NVIDIA's AA modes in-game. Setting AA levels in-game is safer than using the hardware makers' driver overrides and more convenient than game specific profiles. Aside from heavily encouraging developers to enable in-game AA settings when possible, NVIDIA is exploring other options to make the gamer aware of the caveats associated with driver settings and encourage the use of override AA as a last resort.