I understand what you mean, Tim, but no one has solved the problems of using classic color tools with HDR. They're not even sure what to do with anti-aliasing.
HSV only exists to create user interface. It maps the colors to a neat little Hue circle, with the lowest value at 0 degrees, and the highest value to 360 degrees, divided in 6 quadrants. The saturation is the amount of gray the color does not have, i.e. the purity. In high dynamic range, there is no maximum value, and no real "gray" value. To do color correction on HDR, where a channel can possibly be a thousands of time the value of the next, you can work with basic tools such as multiply and additive.
I think you might be misunderstanding the whole gamma correction controls; try to catch my article on the wiki http://softimage.wiki.avid.com/index.php/Gamma%2C_Linear_Color_Space_and_HDR. XSI has always uploaded 8-bit textures to OpenGL. For HDR and EXR, you get to apply a display gamma to these so you can see a better approximation of the textures you're working with. It's not possible to apply a gamma curve after display to OpenGL, at least not in classic OpenGL, so that's the way to do it. In any case, display gamma is something to apply anytime a float image is converted to 8 or 16-bit
------------------
Luc-Eric Rousseau
Team Leader, User Interface
Softimage|XSI
> -----Original Message-----
> From: Tim Leydecker
>
> Hi Luc-Eric,
>
> I donÂt want to be offensive or anything when I
> still find it more failsafe to do image operations
> and manipulations without clipping nowadays.
>
> >With an HDR or EXR images, the pixel buffer
> >given to mental ray when the effects are on is an
> >8-bit image gamma corrected and meant for
> >OpenGL previewing, not a floating point HDR image.
>
> At least this gammacorrection is therfore wrong, imho.
> Only the output from mR and the OGL display should
> be gammacorrected but not clipped beforehead.
>
> I really donÂt want to stirr any mess or resentiments.
>
> ItÂs just that everything and everybody slowly transfers
> over to lossless higher bitdepths for their work, even games
> make use of HDR rendering (mostly blooming highlights),
> it would be great to have XSI do itÂs operations accordingly.
>
> E.g. conceptually adapt working in an unclipped colorspace
> that may even have room for Ultra-HDR or 128bitfull*.exr
> or whatever the next killerformat will be called.
>
> I donÂt want to insist on the NTSC luminance concept either,
> itÂs been an example to illustrate things. HSV imho still works,
> itÂs just more V(alues). Same for H and S. Greyscale HDRÂs
> are actually great for setting up materials well lit but colorproof.
>
> Cheers
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