POV-Ray : Newsgroups : povray.unofficial.patches : UberPOV is back : Re: UberPOV is back Server Time
21 Apr 2024 07:36:52 EDT (-0400)
  Re: UberPOV is back  
From: Mr
Date: 1 Sep 2016 10:10:00
Message: <web.57c835f615c4456616086ed00@news.povray.org>
clipka <ano### [at] anonymousorg> wrote:
> Since I'm no Blender user, I need to do a bit of guesswork here...


Here is the fast illustrated summary of what's available:

https://www.blender.org/manual/render/blender_render/materials/properties/diffuse_shaders.html

In Blender Internal, you specify both a diffuse and a specular shader plus the
fresnel effect used for the "reflection block" which has nothing to do with the
one you can use in the diffuse, the later acts just as if you put some color_map
to alter object luminosity, darkening it along the vector of the lamp directed
at it.
>
> 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 Lommel-Seeliger model, the diffuse brightness instead intensifies.
>

indeed!... But angles to the lamp vector


> > -Lambert with a Normal input ramp?
in Blender you can also use a color_map along the viewing direction, just like
povray slope_map
specifying the "normal" option makes the gradient apply in viewing direction.
whereas "energy" for instance applies it along the lamp vector


> > -Minnaert?
>
> Nope. Again, to the contrary: Minnaert also makes the diffuse component
> fall off at shallower angles.
>

Blender's implementation can also do the opposite: lightening faces as their
normals get perpendicular to the viewing direction, kind of like oren Nayer also
does , but orders of magnitude stronger.  (" if Dark is 1 you get exactly the
Lambertian result. Higher darkness values will darken the center of an object
(where it points towards the viewer). Lower darkness values will lighten the
edges of the object, making it look somewhat velvet")

So maybe we could say that Lommel-Seeliger  is a good model to emulate all
darkness values of Blender Minnaert below 1 wile values above could switch to a
darkening slope_map/aoi pattern ?

And Brilliance parameter would be better to emulate Fresnel as it's more light
dependant than viewing angle dependant???


Anyway, at the moment I meet a bigger issue, as I see no variation when trying
to use the two new models in pov, are they confirmed to work in your Windows 64
build?



The Minnaert shader in POV was the topic of this work:
http://news.povray.org/povray.binaries.images/thread/%3C3f6ccdf7%40news.povray.org%3E/

Has it been used for this feature or can it still be added to all the options?

Thanks a lot to all devs for your work so far!


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