[Radiance-general] Luminance to RGB

[Greg Ward]

Yes, you basically invert this formula.  If you have no color information, you can get a grayscale result by dividing your luminance by 179 and using the result for all three (RGB) channels.  The pvalue program can produce a Radiance picture from raw input values, and the -b option can be used together with -r to take in a single radiance value for each pixel.

-Greg

> From: Ji Zhang <hope.zh at gmail.com>
> Date: July 7, 2011 9:36:56 AM PDT
> 
> Hi, Steph,
> 
> Not sure if it's helpful but please refer to Axel Jacob's tutorial in page 40 (http://www.jaloxa.eu/resources/radiance/documentation/docs/radiance_cookbook.pdf).
> 
> According to Axel, the illuminance value (lux) of a point is calculated by using the following formula:
> Illuminance = 179*(R_irradiance*.265 + G_irradiance*.67 + B_irradiance*.065) 
> 
> I'm not sure if a Luminance value can be converted and split back into RGB radiance values. 
> 
> So, maybe the experts here can give you more clearer advices. 
> 
> - Cheers, Ji
> 
> 
> 
> On Thu, Jul 7, 2011 at 11:57 PM, Art Cygne <artcygne at yahoo.com> wrote:
> Hello
> 
> I need to make the conversion of Luminance values (cd/m2) to the RGB colors to write-in Radiance...
> 
> Can anyone give me a hint of this basic question?
> 
> Thanks in advance.
> 
> Steph