HDR + FSAA: Worth It?

Even though ATI Technologies was a year behind Nvidia in supporting FP16 HDR, the company has managed to offer something that the rival did not consider valuable: full-scene antialiasing along with FP16 HDR. Nvidia had a significant reason not to spend transistors on FSAA support in HDR mode back in the days of the GeForce 6- and the GeForce 7-series, as graphics boards slower than the GeForce 7800 GTX 512 would hardly achieve any decent speed with FSAA and HDR enabled even in Far Cry game.

Yet another reason for not supporting FSAA with FP16 HDR is that even now, two years after the GeForce 6 entered the scene with FP16 HDR support, there are virtually two famous games that take advantage of it: Far Cry as well as Elder Scrolls: Oblivion . Obviously, at some point in future, when more games adopt FP16 HDR, support for FSAA along with it will be compulsory, but now the technology can be enjoyed in very few games. Furthermore, ATI still has not managed to pass WHQL validation with drivers that support HDR+FSAA on Oblivion , which means that even today enabling FSAA along with HDR is not an easy procedure, as gamers have to download special non-WHQL drivers.

Elder Scrolls: Oblivion Quality with and without HDR and/or FSAA
Radeon X1950 XTX
	No HDR	HDR
0x FSAA
2x FSAA
4x FSAA
6x FSAA

As you can see, Elder Scrolls: Oblivion looks remarkable with FSAA and HDR turned on. Unfortunately, we could not obtain the benchmark numbers for you to see, as performance of Oblivion with HDR+AA varies substantially, which does not allow us to present validated benchmark result: every new manual test run brings a new number.

What we can say about current state of HDR+AA support is that it is here, it provides some additional eye-candy and is generally a nice feature. However, given all the difficulties with enabling the capability, gamers should really think twice before considering this feature seriously.

Transparent Textures Antialiasing

Both GeForce 7950 GX2 and the Radeon X1950 XTX support antialiasing of transparent textures that can be enabled and that can benefit quite a number of games.

Both ATI and Nvidia offer their technologies to smooth edges of fences, leafs and so on. ATI calls its technology Adaptive antialiasing and offers Performance and Quality multi-sampling modes, whereas Nvidia names its feature as Transparent antialiasing offering multi-sampling or super-sampling modes. Given that we do know for sure that neither Radeon X1800 nor the GeForce 7800 graphics cards experience even a little performance degradation because of antialiasing of transparent textures, it only makes sense to examine quality of antialiasing in different implementations.

Based on the comparison of the screenshots using the aforementioned Compressonator utility, we can conclude the following:

• Nvidia’s Transparent AA Multi-Sampling hardly does any job at all.
• ATI’s “Performance” Adaptive AA is clearly better than Nvidia’s Transparent AA multi-sampling, but is obviously not as good as “Quality” Adaptive AA.
• Nvidia’s Transparent AA Super-Sampling is a little bit more accurate than ATI’s “Quality” Adaptive AA.

Please note that in case of Half-Life 2 screenshots on the Radeon X1950 XTX hardware, the fence behind Alex (a character of the Half-Life 2 game) is not rendered only on screenshots: during the game we did not experience any artifacts of this kind.