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Radiance's radiation spectrum

asked 2019-03-01 03:41:02 -0500

lassebk gravatar image

updated 2019-03-02 12:53:25 -0500

Dear Radiance users,

I'm trying to do a conversion of unites from irradiance to photosynthetic photon flux density. In order to do a precise conversion, I need to figure out what spectrum Radiance uses for its calculations. I can't seem to find the answer on Radsite.

Thanks for time!

/Lasse Korsholm

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answered 2019-03-04 10:51:13 -0500

Hi Lasse,

You already started a thread on this on Discourse. I recommend we keep this information together there.

In summary, Radiance does not have an explicit spectrum, just three channels for its ray calculation. You are free to assign these channels however you like. Simply adjust your transmittance and reflectance values in the scene description to adhere to the photosynthetic spectrum rather than the photometric one.

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Does this mean we can model the infrared for heating calculations as well?

Determinant gravatar image Determinant  ( 2019-03-04 14:00:58 -0500 )edit

Sort of. Radiance doesn't compute or maintain surface temperatures, which you need to compute longwave radiation in a complete thermal calc.

GregWard gravatar image GregWard  ( 2019-03-04 14:16:34 -0500 )edit

Thanks for that. I'm going to turn this into a question because I'd like to know if there are any step-by-step procedures on how to do this. Looked online and what I could find was old and incomplete. Just saw the unmethours post. will hold off until I explore that.

Determinant gravatar image Determinant  ( 2019-03-04 16:24:38 -0500 )edit

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Asked: 2019-03-01 03:41:02 -0500

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Last updated: Mar 04 '19