[Radiance-general] gensky result different from that in, Axel's tutorial

[Greg Ward]

Just a side-note:  the turbidity factor is _only_ used by gensky to  
estimate the zenith luminance.  If the horizontal irradiance or zenith  
radiance is given using -B or -b (respectively), turbidity is ignored.

Cheers,
-Greg

> From: Axel Jacobs <jacobs.axel at gmail.com>
> Date: June 23, 2010 8:27:12 AM PDT
>
> Hi Ji Zhang
>
> > So, Which output is the correct one? What might causes the
> > differences?
>
> The Radiance Tutorial must be about ten years old now. I keep  
> updating it, fixing small typos and inconsistencies, but have not  
> felt the need to reflect the recent changes to gensky's turbidity.
>
> Both, CIE clear and overcast are extremes that are fairly unlikely  
> to occur in reality. As Greg said, you really need to feed in  
> measurements, and also have a good guess at the turbidity if you are  
> concerned about accuracy. If you can supply diffuse and direct  
> irradiation, you might want to use gendaylit instead.
>
> Axel