[Radiance-general] Modeling an oil lamp source

[Greg Ward]

Hi Lars,

This looks about right.  The value for blue is zero because it's  
actually outside the Radiance color gamut.  If you don't want to use  
a table next time, the conversion from color temperature to CIE (x,y)  
is provided in src/cal/cal/blackbody.cal.

-Greg

P.S.  I'm still waiting on your scene description to sort out the  
other problem with the long rpict start-up time.

> From: "Lars O. Grobe" <grobe at gmx.net>
> Date: April 22, 2008 2:00:49 PM PDT
>
> Hi list,
>
> this is the first time I am using colored light sources, and I am  
> sure that I make some mistakes. So for your amusement and in the  
> hope someone enjoys to show me the worst of my misunderstandings, I  
> post how I try to model a light source, which is to represent an  
> oil lamp.
>
> I estimate a flame with 2cm diameter, 10 lumen,1900 K black body  
> temperature.
>
> I derive rgb 1.00 0.23 0.00 from the color temperature. This is  
> only for the chromacity, and to be honest I did not do the CIE  
> transformations but looked up in a table for 1900K.
>
> I add a line to lamp.tab reading
>
> /oil lamp/	.54 .41 .95
>
> so that I can use lampcolor and reuse my guesses later.
>
> No I run lampcolor, for the lamp type I enter my freshly defined  
> oild lamp, I use meters as length unit, to model the flame I use a  
> sphere geometry, and I give my estimated 0.01m radius for the flame  
> (resulting in a luminaire sphere of 2cm diameter). My guessed total  
> luminous flux is 10 lumens, leading to:
>
> Lamp color (RGB) 28.93 8.62 0.0
>
> Does this make sense? Am I totally wrong? I would apply a light  
> modifier created with these values to a 1cm radius sphere now.
>
> Thanks, CU, Lars.