On 6/15/2012 7:13 AM, Invisible wrote:
> I looked outside a little while ago, and observed that the sky was blue.
>
> But when I asked POV-Ray to do some radiosity with a blue sky, the
> entire scene came out blue. Which, logically speaking, isn't surprising.
> If the sky is blue, clearly it's emitting blue light, which would result
> in everything being illuminated blue.
>
> And yet, when I look outside, the world is /not/ tinged blue. So... WTH?

The blue that you see in the sky is scattered out of some of the 
sunlight that hits the ground, making direct sunlight a little less 
blue.  Things that are in direct sunlight get that plus the blue from 
all over the sky, resulting in white.

On the other hand:

One day while stationed in Germany I got onto the roof of one of our 
buildings to take a picture of the squadron's personnel while they were 
all lined up.  The sun was up, but it was behind the trees (and it was 
mid-winter so it wasn't all that high to begin with), so the squadron 
was lit only by the scatter from the blue sky.  The light all looked 
normal to me, but when I looked at the photographs later on they were 
all tinged with blue.  I'd have to say that my eyes adjusted to the blue 
and gave my brain the adjusted view.

Regards,
John

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