Originally Posted by Subtestube
The X800 *can* do frame buffer blending.. least, that's what I thought. As I understand it, it's just that the accumulation buffer (for blending) on the ATi cards doesn't have high enough precision for true OpenEXR HDR. At least, that's the way I understand it... but on that, I could be wrong, and would be happy to be corrected. I'm really not as knowledgeable about the R420 as I should be.
Edit: Apologies, it seems you're right. Looked it up, and the 420 can do true OpenEXR HDR... but it has to use pixel shaders to do so. I'm still fairly certain it can do a reduced qual version natively though.
according with a huge thread in B3d about FPblending feature in the Nv40 , ATI employees already confirmed that the is NO blending support neither with FP precision,neither with INT precision in ATi hardware. in other words if you are a developer a wants true-HDR in a game ,with ATI hardware then you are out of luck. everything needs to be emulated with pixel shaders through a process that everyone agreeds that is .. very very slow , with lower quality and painfull in the ass to emulate it. which is why the major feature in HL2 is now dropped by Valve because emulating it is not good enough for what they wanted.. Futuremark interview in B3d goes even more saying ATi can't do HDR.. which means -> High
DynamicRange . just because lights in a demo looks overbrighten doesn means its HDR. . just read their interview. lower quality emulation of "Hdr" .. is the only thing you have seen until now in PS2.0x cards demos. Timbury and FArcry are the first aplications to support true HDR in realtime.so take anything that you read from reviews with grain of salt. There are many game developers including Crytek/Futuremark and even Valve with comments already about this. the same things goes for true DIsplacement mapping and hardware Shadow maps.. not supported by ATI.