[Radiance-general] SSLD skies and zenith radiance

[Lars O. Grobe]

Hi,

a short update, for now I am dividing the task to set-up a sky into two 
steps:

1) Create a gensky-description. The zenith radiance as calculated by 
gensky can be found in the skyfunc definition (it is the third number on 
the last line of the output, so it can easily be extracted using awk). 
The horizontal illuminance that is to be found for the ground luminance 
can be either calculated from the sky model using rtrace, or, for skies 
WITHOUT sun, be derived by multiplying the "ground ambient level" by 
pi*179. The sun position can also be read from the comment lines.

2) Set-up the ssld-description using the values found in step 1).

Maybe it would be worth to create a script that can do all that (and 
also set the ssld-coefficients from a look-up table for a given sky type).

Cheers Lars.
> I am looking into the ssld support that Phillip made available, and I 
> found the following in the accompagnying documentation:
>
> "4. Select an arbitrary zenith radiance, Z (eg. 100 W/m2/sr)."
>
> What is the meaning of arbitrary here? The value is used later by the 
> cal-file creating the distribution. I was hoping to create a 
> distribution from the coefficients and the horizontal illuminance, but 
> I do not know where to get data on zenith luminance.

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