[Radiance-general] Candle lighting? rgb values....

[Giulio Antonutto]

I guess what you have to do is to scale the rgb values you have by a factor
that depends on the expected light levels on the table (is there a table?)
 
when you consider light sources modelled with spheres:
 
A= apparent area of the sphere = PI * R^2 [m2]
F= luminous flux [lm]
I = luminous intensity= F/4PI [cd]
L=I/A [cd/m2]
R=L/179 [W/m2] = radiance = your R G B in the ligth definition 
 
E=illuminance on a plane=I * cos3(theta) / h2
 
therefore you have to:
measure the light levels at a given point
from the illuminance you get the intensity
therefore after some number crunching you have the radiance.... ;-)
 
hope it helps,
giulio
 
 

-----Original Message-----
From: radiance-general-bounces at radiance-online.org
[mailto:radiance-general-bounces at radiance-online.org]On Behalf Of John
Sutherland
Sent: 24 March 2004 14:01
To: radiance-general at radiance-online.org
Subject: [Radiance-general] Candle lighting? rgb values....


Ive been setting up candles  and modeling the light source as a sphere
(apparently accurate enough) but after researching through several of
peoples papers on using candles in Radiance i found sets of RGB values.
 
Beeswax 0.502 0.239 0.043
Tallow 0.759 0.240 0
 
But when i use these as my material then apply them to a sphere of size
approx 0.01 they dont appear bright at all, in fact radiance doesn't appear
to light at all with them, decimal values for rgb are way to low. The values
i need are up in the 100's but how can i find out a candles
watts/steradian/m2 RGB values? does anyone have any as reference or know of
any?
 
Cheers John


___________________________________________________________________
Electronic mail messages entering and leaving Arup business
systems are scanned for acceptability of content and viruses.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://radiance-online.org/pipermail/radiance-general/attachments/20040324/ffbd44fb/attachment.html