I use the bent normals option sometimes to render a "normals pass" to
do fake lighting enhancements in some renders in post.
What other uses do you guys give to it? I'd love to know,
Cheers,
-- Alan
On Feb 7, 2008 1:37 PM, guillaume laforge
<guillaume.laforge.3d(at)gmail.com> wrote:
> Hi Amaan
>
>
> >I think the AO node is adding 0.5 to all three XYZ components before
> >sending the output to a Vector2Colour node. The question is, why is 0.5
> > being added?
>
> I guess it is the way to store negative values of the bent normal vector in
> the rgb space. If you render a bent normal "as is" you will clamp the -x and
> -z values to zero.
>
> Cheers
>
> Guillaume Laforge
>
>
>
>
> On Feb 7, 2008 4:44 PM, Amaan Akram <xsilist(at)warpedspace.org> wrote:
> > Hello everyone,
> >
> > I am just trying to get my head around bent normals in Mental Ray --
> > following is my (mis?)understanding of what they are (please correct me
> > if I am wrong)
> >
> > -a bent normal is a direction vector that is calculated by taking an
> > average of all the un-occluded samples fired from around the surface
> > normal of an intersection point
> >
> > -for completely un-occluded areas, a bent normal is the same as the
> > surface normal
> >
> > Based on the above understanding, I run two tests
> >
> > Test case 1
> > Take a default primitive grid, plug a Vector State node straight in to
> > the Surface port of the Material node and set the Vector State to
> > "Normal Vector"
> >
> > Test case 2
> > Take a default primitive grid, plug an Ambient occlusion node straight
> > in to the Surface port of the Material node and set the ambient
> > occlusion output mode to "Return Bent Normals (World Space)"
> >
> >
> > According to my understanding of bent normals, both the above test cases
> > should produce the exact same result--but they don't. The RGB output for
> > the shader in both test cases should be:
> > R: 0
> > G: 255
> > B: 0
> >
> > The above mentioned result is the output of Test Case 1 (with Vector
> > State node), but...
> >
> > in Test Case 2, the RGB output is:
> > R: 127
> > G: 255
> > B: 127
> >
> >
> > I think the AO node is adding 0.5 to all three XYZ components before
> > sending the output to a Vector2Colour node. The question is, why is 0.5
> > being added?
> >
> > Thanks
> > Amaan
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> --
> Guillaume Laforge
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