The look of the image changes when you enable effects because XSI then loads the image, applies the effects, and give that pixel buffer to Mental Ray. When the effects are off, XSI gives the file path to mental ray.
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.
------------------
Luc-Eric Rousseau
Team Leader, User Interface
Softimage|XSI
> -----Original Message-----
> From: owner-xsi(at)Softimage.COM
> [mailto:owner-xsi(at)Softimage.COM]On Behalf
> Of Thomas Helzle
> Posted At: Tuesday, April 04, 2006 2:10 PM
> Posted To: xsi
> Conversation: (*.hdr) environment shader questions
> Subject: Re: (*.hdr) environment shader questions
>
>
> No, the moment you activate the effects, everything outside
> the 0.0 to 1.0 range (that is what "normal" image formats
> use) is cut off (since it is converted to integer 8/16 bit),
> so you loose what makes a HDRI image different - values way
> outside of this range, "whiter than white" as the Persil
> commercial would call it, giving those interesting effects of
> sunlight etc.
>
> In that regard, 8 and 16 Bit aren't different from each other
> as long as they are implemented as integers that are
> translated into the 0.0 to 1.0 range. 16 Bit can represent
> more in-between values, so it can look "smoother".
> Only floating point data can hold HDR information (at least
> this is how it is implemented, basically you could use
> integers too, but you would have to define what the range is).
>
> Hm - was that any clearer?
> Otherwise ask again :-)
>
> Cheers,
>
> Thomas Helzle
>
> On Tue, 04 Apr 2006 19:43:52 +0200, Tim Leydecker
> <BauerOink(at)gmx.de> wrote:
>
> > Hi Luc-Eric,
> >
> > thanks for pointing out the manual, will give it another go :-)
> >
> > So, as far as I get it, when my renderregion changes the
> > moment I "enable effects" on the environmentshader Âs
> > image "Adjust" page, this is due to the display gamma
> > setting of the renderregion. IÂll check my preferences
> > settings.
> >
> > When I asked about the 8-16bit conversion I expected
> > it to be a convenience hack for using lowdynamicrange
> > images as the input for lighting calculations of FG.
> > DidnÂt realize itÂs mostly meant for displacementmaps.
> >
> > What IÂd want is to load a *.hdr image, render using itÂs
> > linear float input, probably *see* the gammacorrected
> > input to correctly set the f-stop and have the renderregion
> > and OGLviews display things gammacorrected. Oh, my:-)
> >
> > Now IÂll check the wiki again.
> >
> > Cheers
---
Unsubscribe? Mail Majordomo(at)Softimage.COM with the following text in body:
unsubscribe xsi
