[Bf-cycles] Realistic Nk-Data Metal BSDF

[Lukas Stockner]

Hi,
I agree, Vector sockets sounds reasonable. Concerning fresnel_conductor(): I 
have looked into it, but it uses scalars for eta and k, so this would need to 
be changed. This shouldn't be a problem through, since nobody uses it. I'll 
just change it and send the patch to developer.blender.org (I will also change 
the sockets to Vector, but that still remains uncertain).
Thanks for the feedback,
Lukas

Am Donnerstag, 26. Dezember 2013, 19:23:48 schrieb Thomas Dinges:
> Oh and I forgot, we already have a fresnel_conductor() function, which
> is currently unused in bsdf_util.h, maybe you can re-use that?
> For OSL you would need to copy the code into node_fresnel.h, and include
> this in the OSL shader then.
> 
> Am 26.12.2013 19:17, schrieb Thomas Dinges:
> > Hi,
> > looks good already, thank you.
> > 
> > I wouldn't go with color sockets, that is weird, as the resulting color
> > is not what the user sets. Probably it would be better to use vector
> > sockets for this, but I leave this decision to Brecht. (We already use
> > the Vector socket for SSS RGB Radius).
> > 
> > As for presets, not sure. We don't have presets yet for (Shading) Nodes,
> > but maybe this could be added.
> > 
> > Also on a side note, maybe you'd like to use this here to upload
> > patches: https://developer.blender.org/differential/diff/create/
> > This way its easier to review the code and we have all infos/patches in
> > one place. :)
> > 
> > Best regards,
> > Thomas
> > 
> > Am 26.12.2013 17:45, schrieb Lukas Stockner:
> >> Wow, adding a node was really difficult, but I got it working. Attached
> >> is a patch that adds a "Conductive BSDF" which just calculates
> >> reflectance based on the Fresnel equation for conductors.
> >> 
> >> Its inputs are Eta and K, the coefficients of the complex IOR, and
> >> Roughness. It supports Sharp, Beckmann and GGX microfacets. Performance
> >> and sampling look just as good as the Glossy BSDF. I haven't tried the
> >> OSL version yet since I can't get it to build, but the shader itself
> >> works in standard 2.69.7 in the script node. GPU should work, but not
> >> tested since my GPU still is Compute Capability 1.3.
> >> 
> >> Two questions remain: First, how should the ETa and K values be input?
> >> Currently, since thay are RGB, they just show up as a color. However,
> >> their
> >> compontents can easily reach 5 and higher. 6 Sliders, on the other hand,
> >> ane probably overkill. Second, should there be a set of preset
> >> coefficients to choose from (like in the LuxRender plugin), or just a
> >> list somewhere in the Wiki?
> >> 
> >> I have rendered a simple demo, the image is on
> >> http://postimg.org/image/70vyf00yp/ . From left to right, the materials
> >> are: Silver, Gold, Chrome, Copper and Aluminium. The coefficients are
> >> simply from multiplication of the PBRT measurements with the CIE XYZ
> >> curves and a transform to sRGB. If someone is interested, I could post
> >> an Octave script for it.
> >> 
> >> Lukas Stockner
> > 
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> > Bf-cycles at blender.org
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