[Radiance-general] RGB to Radiance definition

[t.mcminnAocpms.com.au]

Hello Germán,

Have a look at Mark Stocks comment on converting RGB values 
http://www.radiance-online.org/pipermail/radiance-general/2011-April/007743.html

Regards

Terrance

On 23/06/2016 4:00 am, Germán Molina Larrain wrote:
> Dear All,
>
> I am trying to integrate easier ways of defining materials in
> Groundhog, for which I have the following doubt. How can I define a
> Radiance material (i.e. plastic, metal, glass, etc.) from an RGB
> combination and the global Reflectance (transmittance)? The purpose of
> this is to enable "eyedropping" a color, and assigning a reflectance
> or transmittance to it.
>
> What I initially did was to find the combination of RGB reflectances
> that satisfied the rho = R*0.265 + 0.67*G + 0.065*B while maintaining
> the original proportions of RGB. However, since the RGB color that
> comes from the eyedropper has Black/White components (which intend to
> emulate shadows and different light exposures), my procedure often
> ends up returning an R, G or B channel that is greater than 1.
>
> I guess my question is: Is there any way of reconstructing the R, G
> and B reflectances (or transmittances or whatever) from an RGB pixel?
> Maybe playing with HSL space or something?
>
> Best,
>
> Germán
>
>