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

[Georg Mischler]

John Sutherland wrote:

> 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?


A typical wax candle emits about 1 cd of light, that's how the
candela unit got its name. If you take a sphere with a diameter
of 1 cm, then you get an emitting surface of 0.000314 m2.
The luminance is therefore 1/0.000314 = 3183.10 cd/m2.
In Radiance terms this is  3183.1/179 =   17.78 W/sr*m2.

The (weighted) average of your RGB values should be roughly the
same as that. The values you have above only specify the color
proportions, which you need to scale accordingly.


-schorsch

-- 
Georg Mischler  --  simulations developer  --  schorsch at schorsch com
+schorsch.com+  --  lighting design tools  --  http://www.schorsch.com/