[Radiance-general] METAL material values

[Adriana Lira]

Hi Lars,

Thank you so much for your time! This has been extremely helpful.

Best,
Adriana

2008/8/21 Lars O. Grobe <grobe at gmx.net>

> > Then, my question is: what is the difference between "Total Reflection %"
> > and "Specular Reflectivity %", and how does this translate in the METAL
> > material values?
>
> Hm, I hope I do not write something wrong now...
>
> The total reflection is the relation of energy reflected to the energy
> that is hitting the surface. 100 hit the surface, so, if total
> reflectivity is 95%, 95 leave it.
>
> Specular reflectivity is the part of what is reflected that is leaving
> the surface in a directed manner. So to go on with our example, is 95%
> was the total reflection, and the specular reflectivity is 90%, of the
> 100 hitting the surface 0.9*95=85.5 leave the surface as specular
> reflection. That also means that the remaining 0.1*95=9.5 leave it as
> diffuse.
>
> My total unitless numbers would all translate into radiance Watt / (sr *
> m2).
>
> > My other question is still about the value ranges:
> >
> > What are the maximum values for "specularity" and "roughness". I would
> like
> > to confirm if the maximum value for specularity is 1.0 (or maybe more?)
> and
> > if the maximum value for roughness is 0.5 (although I have found in some
> web
> > links that roughness values greater than 0.2 are not realistic)
>
> Specularity cannot be more then 1, as you cannot have more energy
> reflected as specular then energy reflected in total. If you replace the
> maximum 1.0 by 100% you will understand.
>
> As far as I know you are right about roughness, but it is difficult to
> estimate this parameter, and I treat it more as a visual effect...
>
> CU Lars.
>
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>


-- 
Dr. Adriana Lira-Oliver
DDes I MDes I Barch
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