

Am 01.09.2016 um 10:54 schrieb Mr:
> Though I already spent quite some time to emulate Blender Shaders in POV as they
> get exported, I would like to try to link the exporter to these new shading
> models to find out if it gives closer results.
>
> Oren Nayar seems straightforward because Blender has its implementation of that
> very model, but what would you say is the closest to LommelSeeliger in Blender
> shading models?
Since I'm no Blender user, I need to do a bit of guesswork here...
> Fresnel?
Nope. Fresnel isn't actually a shading model, but rather a mathematical
term that appears in various shading models. From what I gather on the
internet, it seems that in Blender you can slap it onto every proper
shading model as an option (whether it makes sense or not; I suspect
some models may be sophisticated enough to already account for the
fresnel effect by themselves), and you can do the same in POVRay 3.7.1
by using the `fresnel` keyword directly in the `finish` block.
To the contrary: As you view the surface at a more shallow angle,
applying a Fresnel term will make the diffuse component fall off; using
the LommelSeeliger model, the diffuse brightness instead intensifies.
> Lambert with a Normal input ramp?
Dunno. I wasn't able to find any reference to "Normal input ramp" on the
Internet, so someone would have to explain to me what a "Normal input
ramp" is, and how it would be plugged into the Lambert model.
> Minnaert?
Nope. Again, to the contrary: Minnaert also makes the diffuse component
fall off at shallower angles.
I suspect LommelSeeliger is no suitable substitute for any of the
Blender shaders. And if you were to try to go the reverse route and try
to simulate LommelSeeliger in Blender, a mix of Lambert and OrenNayar
with a particular set of parameter settings (possibly 100% roughness,
but that's just a quick guess) might actually be the best approximation.
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