[Bf-cycles] Realistic Nk-Data Metal BSDF

Thomas Dinges blender at dingto.org
Thu Dec 26 19:23:48 CET 2013

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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