[Radiance-general] Can this be done with pcomb?

[Greg Ward]

The short answer is 'yes.'  Light is linear, so you can always scale  
according to window transmittance for light coming through the  
window.  There may be some (very) slight inaccuracies due to the  
varying angular transmittance, but the results should be roughly  
correct.

If the window is the only source of light in the room, and you are  
adjusting the picture exposure rather than looking at the luminance/ 
radiance values, then you will see no change at all, because one will  
compensate for the other.

-Greg

> From: "Autif Sayyed" <AutifS at TWGI.com>
> Date: June 10, 2010 9:23:36 AM PDT
>
> Hello All,
> I have a pic file of an indoor scene with windows that I want to  
> test with varying visible transmittance of the glass. Without having  
> to run rpict again, is there a way of dropping down the sky  
> luminance using a multiplier OR to uniformly drop down the light in  
> the scene by combining the pic (using pcomb) with pic file of a  
> screen of a specific transmittance? In other words, can I just  
> filter down the light levels uniformly in the scene without having  
> to run rpict again.
> Thanks.
> Autif