[Radiance-general] inquiry on the possibility of colored LED light simulation in Radiance

[Greg Ward]

Well, the general approach to measuring reflectance is to shine a light of the appropriate spectrum on the surface and determine what fraction reflects back.  This is typically accomplished with an integrating sphere if your surface is Lambertian or approximately so.

If you have full spectral reflectance data, you can multiply these measurements against the spectral emission of your different LED illuminants to get the appropriate channel responses.

I hope this helps.
-Greg

> From: "Randolph M. Fritz" <rmfritz3 at gmail.com>
> Subject: Re: [Radiance-general] inquiry on the possibility of colored LED light simulation in Radiance
> Date: November 26, 2015 6:41:10 PM PST
> 
> I just entered "spectral reflectance of leaves" into Google, and a whole bunch of material popped out. It looks like there is actually a fair bit of research on this.
> 
> -- 
> Randolph M. Fritz, Lighting Design and Simulation
> +1 206 659-8617 || rmfritz3 at gmail.com
> 
> On Thu, Nov 26, 2015 at 5:24 PM, alexander jiang <jiangalexander1989 at gmail.com> wrote:
> Hi Greg,
> 
>  
> 
> Thanks for your info so much.
> 
>  
> 
> But I am still confused about what you mentioned in the previous email ‘can characterize the reflectances of materials in each of these spectra, probably through measurement”.
> 
>  
> 
> For instance, the green crops will be the objectives in the greenhouse environment I plan to simulate, what specifically you mean ‘can characterize the reflectances of materials through measurement”
> 
>  
> 
> Regards,
> 
> Alex
> 
>  
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>  
> 
>  
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> 
> From: Greg Ward [mailto:gregoryjward at gmail.com] 
> Sent: Thursday, 26 November 2015 8:53 AM
> To: Radiance general discussion <radiance-general at radiance-online.org>
> Subject: Re: [Radiance-general] inquiry on the possibility of colored LED light simulation in Radiance
> 
>  
> 
> Hi Alex,
> 
>  
> 
> The RGB channels can represent any spectral content, so if you have 3 (or fewer) illuminant spectra, and can characterize the reflectances of materials in each of these spectra, probably through measurement, then you can get accurate results from Radiance.  If you have more than 3 spectra you want to try, you can perform sequential runs accordingly.  It's a bit tedious, but people have done it.
> 
>  
> 
> Cheers,
> 
> -Greg
> 
> 
> 
> 
> From: "alexander jiang" <jiangalexander1989 at gmail.com>
> Subject: [Radiance-general] inquiry on the possibility of colored LED light simulation in Radiance
> Date: November 25, 2015 5:55:21 PM PST
>  
> Hi All,
> 
>  
> 
> Currently I was involved in a research on how different coloured LEDs and the optimal intensities affect plant growth and qualities.
> 
>  
> 
> After reading through some info online, I know that it is okay with simulating sunlight in Radiance but am not sure if it is possible to simulate different coloured LEDs (such as red , blue, orange, etc)?
> 
>  
> 
> Regards,
> 
> Alex
> 
> 
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