Forums Technical Discussion Back lit single sided geo SSS with principled shader

Back lit single sided geo SSS with principled shader

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Simon van de Lagemaat2
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Shading some grass right now and applying SSS with the principled shader on thin walled geo results in nothing, just black. What's the proper workflow for diffuse style transmission? So far I've only gotten single scatter on the classic shader to work.
Simon van de Lagemaat
owner the Embassy VFX
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jsmack
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You can, but it's broken, you can make it work with:

vector diff_color,trans_color;
bsdf f;
vector nn,ni,tng;
diff_color = set(0.1,0.35,0.001);
trans_color = set(0.05,0.15,0.0001);
nn = normalize(N);
ni = normalize(I);
nn = frontface(nn,ni);
tng = select(dot(nn,Ng),Ng,-Ng);
f = 2.0 * ( diff_color * diffuse(nn,tng,"label","diffuse") + trans_color * translucent(-nn,-tng,"label","refract") );

then add the render property:
vm_smoothP “Fix Shadow Terminator”
and disable it.
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tamte
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you should be able to just use PBR Diffuse VOP with inverted normal, you can name the component “refract” or maybe “sss” if you want
and just layer that with your mat
Edited by tamte - March 15, 2017 18:22:01
Tomas Slancik
FX Supervisor
Method Studios, NY
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Simon van de Lagemaat2
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tamte
you should be able to just use PBR Diffuse VOP with inverted normal, you can name the component “refract” or maybe “sss” if you want
and just layer that with your mat

Thanks! both of you! I also forgot about the translucency refract model in the classic shader. It would be nice if the principled shader supported translucency. This is one of its blind spots.
Simon van de Lagemaat
owner the Embassy VFX
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