[Radiance-general] Radiance's optics

[Germán Molina Larrain]

Thanks for the quick response Bob!

It is a little bit clearer now, But. the radiance considered by the
software is, then, only the visible part of  the sun's radiance? If I
wanted to compute the total solar radiation (including IR and UV). Should I
compute (,265*R+.67*...)/vf ; where "vf" is the visible fraction of the
solar spectrum?


Thanks Very much!



2012/11/28 Guglielmetti, Robert <Robert.Guglielmetti at nrel.gov>

> Hi Germán,
>
> Radiance (the software) does indeed work in radiometric values at its
> core, and the 179*(blah blah blah) is a valid conversion to illuminance. If
> you have very saturated colors in your model, I suppose they could throw
> off the calculation, but I think it'd take a lot to affect the accuracy.
> That said, this is why I do all of my modeling in greyscale, and use the
> "white" light source color for all electric lights.
>
> There are a bunch of posts in the archives about this topic, and doing a
> higher resolution spectral rendering, and the validity of the 179
> multiplier (which is somewhat arbitrary, but as long as you use that same
> multiplier going in each direction, you should be good to go.
>
> Rob Guglielmetti
> National Renewable Energy Laboratory (NREL)
> Commercial Buildings Research Group
> 15013 Denver West Parkway MS:RSF202
> Golden, CO 80401
> 303.275.4319
> robert.guglielmetti at nrel.gov
>
>
>
> On 11/28/12 12:26 PM, "Germán Molina Larrain" <gmolina1 at uc.cl<mailto:
> gmolina1 at uc.cl>> wrote:
>
> Hello Radiancers,
>
> I am a new Radiance user/developer, and I am working on the calculation of
> Solar Heat Gain through complex fenestration systems. I started learning
> Radiance some time ago, and just an hour ago, a pretty obvious doubt came
> to my mind:
>
> If RADIANCE uses the RGB optical properties (that is, visible spectrum, I
> suppose); how comes that it calculates the Radiance instead of Illuminance?
> If the materials change the spectrum of the radiation in every bounce, how
> is it possible to just use the classic "179*(0,265*R+0,67*G+0,065*B)" to
> compute the illuminance?
>
> THANKS VERY MUCH
>
> Germán Molina
>
> PS: Sorry to bother with rookie questions, but I am the only person in my
> University using RADIANCE.
>
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