Am 31.03.2016 um 21:08 schrieb Le_Forgeron:
> Le 31/03/2016 19:27, clipka a écrit :
>> oren_nayar ROUGHNESS
> 
> ok... what is a good value, excepted for 0.0 which disable it ?
> 
> No link to equations, no idea about what is sigma.

It's the standard deviation of the facet slopes, and can range anywhere
from 0 to just short of infinity. Something around 0.3 might be a good
place to start.

> It also seems the parser allow both oren_nayar & lommel_seeliger at the same time.
> Is it intended ? Is there a fusion of models (when neither is 0) ?

Strictly speaking, with the current implementation a non-zero
lommel_seeliger setting gives you an average not of the Lommel-Seeliger
and Lambertian models, but of the Lommel-Seeliger and Oren-Nayar models,
with the Lambertian model just being the sigma = 0.0 special case thereof.

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