nVidia's response to Valve

[tEd]

Over 1200 views since I posted my question & no answers?

Ok then, lets try it this way:

Dave,

Wanna explain why you think HDR needs DX9 & PS2.0 when it evidently doesn't or why you feel the nV drivers don't support HDR when many ppl can run both the ms & rt HDR demos w/nV DX9( :? ) cards & drivers? 8)

Thnx,

maybe because

Additionary, D3DFMT_A16B16G16R16F and D3DFMT_A16B16G16R16 texture formats that can be rendered are highly recommended. If the current Direct3D driver doesn't support any floating point texture formats, Depth Of Field and Halo effects will not work. And if doesn't support any high-precision formats (at least 16-bit floating point or integer per component), both of the image quality and the frame rate will be down

 

[GameCat]

While it's not actually possible to achieve high dynamic range (i.e represent numbers with very large difference in magnitude such as 0.001 and 1000000000) with any sort of precision in integer, you *can* do image based lighting with a fudged high dynamic range on DX8 hardware. There's a paper on this by Debevec IIRC, might have been Heckbert (might have been both . One simple way of doing it is storing "extra bright" info in alpha for colours that are outside the normal [0,1] range. You can then utilise that to get overbrightening and/or that glow effect.

In summary: It's certainly possible but it's less general, lower quality and harder to implement.

 

[just me]

Thanks GameCat. 8)

That's my laymans understanding of it: it can & has been done, but Valve just isn't going to do it for DX8-8.1 card owners. I realize M$ is backing HL2 & it is the future of the rendering, but it seems a tad lazy of Valve to focus solely on DX9 when DX8-8.1 still has so much to offer > albeit a tad slower & not as 'pretty'.

Maybe one of the 'plugins' on the net will allow it for 8-8.1 card owners w/a 'toggle' in case frames do drop below the end users desireable level. I can hope anyway.

There's a paper on this by Debevec

http://athens.ict.usc.edu/Research/IBL/

From 1998. It's too tech for me to understand fully, but I'm sure Valve understands how to do it.

Debevec was at Siggraph 2003 & did a presentation too. http://www.debevec.org/HDRShop/

I have some more reading to do, but I can't understand why Valve won't consider HDR for DX8-8.1 & make it 'toggle' friendly for us.

Anyone else care to share? 8)

 

[WaltC]

Thanks GameCat. 8)

That's my laymans understanding of it: it can & has been done, but Valve just isn't going to do it for DX8-8.1 card owners. I realize M$ is backing HL2 & it is the future of the rendering, but it seems a tad lazy of Valve to focus solely on DX9 when DX8-8.1 still has so much to offer > albeit a tad slower & not as 'pretty'.

....

It just seems to me that as DX9 has been out now for several months...and DX8 has been with us for a couple of years now, and as the IHVs are all advertising and selling DX9-compliant products into the market, and have been for months--it doesn't seem as if there's any reason for developers to eschew DX9. I mean, when DX8.1 hit the streets I don't recall much sentiment for DX7 as having so much to offer. Indeed, most people were impatient to see 8.1 supported by the IHVs, as I recall. Now that we're getting getting real game support for DX9--it seems to me it's coming much faster than support for 8.1 appeared. I can't see a problem with what DX9 developers are doing. Can it really be said to be a developer's fault that an IHV's hardware, sold and advertised as DX9-compliant, comes up short on the DX9 feature-support list?

 

[GraphixViolence]

I think it's a valid generalization that any effect you can program with DX9 shaders could be approximated using earlier versions of the API. Of course, the farther down you go, the more difficult it gets to make the effect simultaneously look as good or run as fast. At some point, it's just no longer worth the effort.

If it's true that HL2 uses ~1200 shaders, it's probably just not feasible or worthwhile to optimize all of them to run on DX8 hardware.