OpenEXR HDR And Anti-Aliasing At The Same Time?
When planning this article, we were looking forward to demonstrating the ability of the Radeon X1000 cards to enable both Shader Model 3.0 compliant HDR and anti-aliasing at the same time. This is a feature that GeForce 6 and 7 generation hardware is not compatible with, so we wanted to see if it was viable on the X1800 GTO. We also wanted to know if it was enough of a differentiator to tip the scales in the card's favor... or if it crippled performance so much that the feature was useless.
The two games that support this feature - both unofficially - are Far Cry (with the 1.4 beta patch) and Oblivion (with ATI's beta "Chuck" driver release).
In the case of Oblivion, we were completely unable to get the "Chuck" patch to work with the X1800 GTO. We tried multiple driver installs, and both released versions of the patched driver, all to no avail. Yes, the driver worked, but screenshots proved that no anti-aliasing was being applied. When we tried a Radeon X1900 XTX in the test bed, the "Chuck" patch worked for a limited time, and then stopped as well - it allowed for HDR but applied no anti-aliasing in the game.
In the case of Far Cry, the 1.4 beta patch is supposed to allow HDR and AA at the same time. Once again, we were unable to get the feature working with the X1800 GTO. When we tried the Radeon X1900 XTX, the features worked for a short time with 2xAA. Unfortunately, it would allow no higher levels of AA, and it was difficult to re-enable even 2xAA in subsequent tests.
Without more time and multiple test beds, we are forced to conclude that there is either something wrong with our test bed, or the Far Cry patch / Oblivion "Chuck" Drivers are a bit unstable. Since other sites seem to have had success enabling this feature, we are suspicious of our test bed, so this is something we may revisit in detail at a later date.
To be sure, there are reports of other people having difficulty getting these workarounds to work as well. In addition, Crytek is rumored to be releasing an 'official' 1.4 patch to support HDR & AA in ATI cards sometime in the near future, so we will keep you informed of developments.
