[Radiance-general] FW: Gensky Question

[Gregory J. Ward]

The glow computed for the ground includes whatever sunlight should be  
falling on it.  An intermediate sky has some sun, so the solar  
irradiance (-R) setting has an effect.  (Even if you use -i or -s,  
gensky still computes the ground radiance based on the sun being out  
-- it just leaves off the solar source.)

-Greg

> From: "Phillip Greenup" <Phillip.Greenup at arup.com>
> Date: November 22, 2006 4:08:25 AM PST
>
> Well this is a funny little thing...  Giulio has found something
> strange!
>
> Having followed his test below, both sky definitions provided a global
> irrad of 55.7 W/m2.  The reflected ground glow was 5.27 W/m2/sr for  
> the
> former model and 3.57 W/m2/sr for the latter.  These correspond to
> ground reflectances of ~30 and 20% resp...
>
> Like Giulio, I have never noticed this as I prefer to use a local  
> ground
> plane, particularly where sunlight is involved...
>
> What's going on here?
> Hmmmmm...
>
> Phil.
>
> -----Original Message-----
> From: On Behalf Of Giulio Antonutto
> Sent: 22 November 2006 11:27
>
> Indeed Phil is right!
> oops :-)
>
> but be careful when you use the options -i and -s, without the sun you
> need also to say -R 0.
>
> If not the 20% ratio will not work, because the ground will include  
> the
> reflected sun component anyway...
>
> Try to compare:
>
> gensky 12 12 12 -i -B 56
>
> and
>
> gensky 12 12 12 -i -B 56 -R 0
>
> The ground is different.... why is it?
>
>
> Phil, what do you think? Can we call this a bug?
>
> I never noticed it before because I do not model the ground with a
> glow...
>
> Ciao,
>
> :-)
>
> G.