Re: tuning ambient occlusion dark/bright input using a custom curve?

["guillaume laforge" <guillaume.laforge.3d(at)gmail.com>]

Sorry, I didn't notice you need it with "Sampled environment". As you need the rvb value, adding a color corrector after the occlusion node will work.

 

You can color correct the environment map too if needed ( in fxtree for example ).

 

If it really doesn't do the job you can break the occlusion and the environment color into two occlusion nodes.

 

Set the first node to "occlusion using bent normal" and plug it  in the gradient. Set the second node to "Sampled environment" with a super small  "max distance" ( 0.001 for example ). Mix the two nodes in multiply mode.

 

It should be a little bit slower than a single occlusion node in "Sampled environment" but not too much with this small "max distance".

 

However I never feel the need to use such render tree, it is just an idea ;-).

 

Cheers, 

 

 

 

 

 

 

 

 

On 4/30/06, Tim Leydecker <BauerOink(at)gmx.de> wrote:

> Hi Guillaume,
>
> changing the interpolation type alone (linear/cubic) helps in
> getting a "softer" tonalmapping but kills the colors when I
> pipe in an environment sampled AO.
>
> It seems just about any node that´ll result in the autocreation
> of an extra Color2scalar node will do this, e.g. automatically
> convert to my input greyscale...
>
> I´m still not an expert user in XSI, my impression may therefrore
> be based on limited experience but I still find the available nodes
> for the rendertree *limiting* - compared to my (still also limited)
> experience with complex shading networks in Maya hypershade.
>
> In respect to the mib_ambient_occlusion, I should have asked if
> there is an internal interpolation/conversion added to tonemapping
> between Bright and Dark color, e.g. a gammacorrection, that could
> be switched off?
>
> Cheers
>
> tim
>
> P.S: I´ve spent waaaay to much time on all this, didn´t expect to
> find so many differences in the way shaders need to be set up in
> XSI compared to Maya, e.g. getting used to the workflow.
>
>
>
>
>
>
> ----- Original Message -----
> From: "guillaume laforge" <
> guillaume.laforge.3d(at)gmail.com>
> To: <XSI(at)Softimage.COM>
> Sent: Sunday, April 30, 2006 9:30 AM
> Subject: Re: tuning ambient occlusion dark/bright input using a custom curve?
>
>
> Hi Tim,
>
> Nodes > Mixers > Gradient. Set it to black and white and plug your occlusion
> shader in the gradient input.
> Then you can change the "mid color" slider or add some colors in this
> gradient to control the dark/bright from occlusion as you want.
>
> Cheers.
>
>
> On 4/29/06, Tim Leydecker <BauerOink(at)gmx.de> wrote:
> >
> > Hi folks,
> >
> > I´m currently trying both mib_ambient_occlusion and the
> > XSI 5.01 XSIAmbientOcclusion shader as a lightshader
> > (e.g. sampling an environment texture) as described here,
> >
> > 
> http://www.lamrug.org/resources/doc/occlusion_tutorial.pdf
> >
> > setup basically similar to pages 9 and 19, exept that I use
> > a tiny 8bit file to reduce the amount of sampling rays
> > required for clean results, also because I don´t have
> > access to a fully functional *.exr creation/manipulation app.
> >
> > the results are quite fine allready (Thanks again to Harry Bardak)
> > but now I´d like to improve the  tonemapping between Bright
> > color and Dark color, like using a gradient/curve to soften the
> > effect in heavily occluded areas *without* simply turning up
> > the Dark color value. Is there a way to do this without piping
> > a colorcorrection node inbetween the AO_out and (material)ambient?
> >
> > I don´t want to chop into my tonalrange by stretching things out
> > but would like to have extra steps...or is there enough room for
> > CC in the rendertree (e.g. 32/64bit calculation)?
> >
> > To get an idea what I look for, please compare the images of
> > mib_fg_occlusion and mib_ambient_occlusion on page 19
> > of the above *.pdf (Thanks for putting it together guys!).
> >
> > You´ll notice the FG occlusion looks more *elegant* compared
> > to the mib_occlsion looking like it´s been *autocontrasted*.
> >
> > Any help appreciated, as I said, my results are rewarding allready
> > (given my level of experience and ressources) but I still try to
> > improve...
> >
> > Cheers
> >
> >
> > tim
> >
> >
> >
> >
> >
> > environmet
> >
> >
> > ---
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> >
>
>
>
> --
> Guillaume Laforge
> freelance TD | cg Artist
>
>
> ---
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-- 
Guillaume Laforge
freelance TD | cg Artist