[Radiance-general] accounting for irradiance due to ultraviolet in rtrace

[Robert Ong]

Hi Lars and Chris,

Thank you all for constructive discussions.

I should've pointed out earlier that I'm only a novice user in Radiance.

@Lars: do you mean like this? rcalc -e '$1=($1*0.33+$2*0.33+$3*0.33)' or 
rcalc -e '$1=0.4*($1*0.265+$2*0.67+$3*0.065)' ? the factor of 0.4 comes 
from dividing the wavelength spectrum of UVR (120-400nm) to PAR 
(400-700nm)...

@Chris: do you mean I should scale my source and material definition by 4?

My apology if I didn't grasp your points clearly.

Thanks once again for your time and attention.

Kind Regards,
Robert


On 21/10/11 16:49, Lars O. Grobe wrote:
> Hi!
>
>> I'm wondering how to account for the irradiance caused by UV in rtrace.
>> I know by default (visible light) this is normally implemented
>> irradiance = 0.265*R_illum + 0.67*G_illum +0.065*B_illum
> That assumes useage of the three channels for RGB. If you decide to use
> another wavelength range, you have two options:
>
> 1) Use one of the three channels for that wavelength range - and then,
> use the radiance covered by that channel, so no summing up of channels.
>
> 2) Set all three channels to the same. E.g. use all three with equal
> values for your UV range. That means a "grey" image. Then you can use
> any channel to get results. Advantage is that in some few places in the
> code, useage of the three channels for RGB is assumed. This might lead
> to some wrong weighting if you choose option 1), so 2) seams to be
> preferable here.
>
> Besides, laws of physics apply...
>
> Cheers, Lars.
>
>
>
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