Originally Posted by Nv40
"True" HDR lighting (64bit FPblending/filtering),is possible only in the NV40.. (thanks to another feature that is not part of SM3.0 yet) very easily. in the ATI cards nothing like that exist. so HDR lighting is done with many limitations to the point that now many incoming games will use HDR lighting but only in the NV40 hardware.(SplintelCell3/Unreal3 and others). Developers like valve$$ will not have a choice$$ to do HDR in the limited situations that ATI R3xx/R4xx hardware can do it ,using workarounds and in the hard way.
The method currently used on ATI cards is "True" HDR and has been available on R300 cards for almost two years now. NV still doesn't have it in any currently available card.
Besides even when the 6800 line finally hits the shelves in June, no game on the planet will attempt to implement 64bit FPblending/filtering on NV40 hardware. It would end up being a slideshow. It is a useless feature to gamers. NV probably put that in for the Pro Graphic workastation cards. Besides even when the game devs pop HDR into a game and decide to use these so called "hacks and difficult workarounds" it will still run twice as fast on an X800 as compared to any NV40.