Hello,

I am using RSENSOR on an array of "test points" for my greenhouse energy

modeling project. In general, I want to model energy arriving at different

points in the greenhouse, given weather conditions, building geometry, etc.

At each test point/sensor, I want to send backwards rays at evenly-spaced

azimuthal angles and polar angles and sum the irradiance contributions from

each ray.

I assumed that RSENSOR does what I intend to do and that my sensor file

will determine what rays are sent and in what direction. But I don't know

whether my assumption is true.

Also, I don't understand what the sensitivity values on the SPOT matrix

really mean. Overall, I just want to calculate irradiance values at each

test point by evenly sampling backwards rays in all directions.

I've looked at this:

However, I don't understand the sin/cosine parts and I am focused and

radiometric units, not human-centered units like luminance.

Thank you!

Best,

Valerie

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Valerie Tan

Computer Science

College of Engineering

Cornell University '19

Bonjour,

Je suis actuellement en vacances. Je serai de retour le 8 janvier 2018.

En cas d'urgence, vous pouvez toujours appeler le numéro général d'Estia : +41 (0) 21/510.59.59 ou envoyer un mail à l'adresse [email protected].

Pour toutes questions relatives à DIAL+, merci d'utiliser l'adresse mail [email protected].

Cordialement

Julien Boutillier

Estia SA

Hi Valerie,

If you just want irradiance at specific points, you should use rtrace with the -I+ (capital 'i') option. Rsensor is not needed unless you have a custom sensitivity distribution you are integrating. If you give rtrace a list of coordinates and hemisphere (surface normal) orientations, you will get out a list of RGB irradiance values (watts/sr/m^2):

positions.txt:

10 15 3 0 0 1

10 20 3 0 0 1

15 15 3 0 0 1

15 20 3 0 0 1

command: rtrace -h- -I+ -ab 1 scene.oct < positions.txt > results.txt

The output file will contain 3 values per line, corresponding to RGB irradiance at each point in the order given.

The "-ab 1" option is needed to turn on interreflections. A more accurate calculation will result from "-ab 2" or "-ab 3". You can also employ multiple processors using the "-n" option, but be sure to add a "-af scene.amb" option to share cached values for a more efficient calculation if you do that.

There are many other options you may consider changing to improve the speed/accuracy trade-off. If you have only a few points, I might suggest something like this:

rtrace -h- -I+ -ab 3 -aa 0 -ad 4096 -lw 1e-5 -n 8 scene.oct < positions.txt > results.txt

The "-n 8" is appropriate for an 8-core machine, but if you only have a few points, the calculation will take just seconds in any case.

Hope this helps!

-Greg

## ···

From: Valerie Tan <[email protected]>

Date: December 28, 2017 9:17:49 AM PST

Hello,

I am using RSENSOR on an array of "test points" for my greenhouse energy modeling project. In general, I want to model energy arriving at different points in the greenhouse, given weather conditions, building geometry, etc. At each test point/sensor, I want to send backwards rays at evenly-spaced azimuthal angles and polar angles and sum the irradiance contributions from each ray.

I assumed that RSENSOR does what I intend to do and that my sensor file will determine what rays are sent and in what direction. But I don't know whether my assumption is true.

Also, I don't understand what the sensitivity values on the SPOT matrix really mean. Overall, I just want to calculate irradiance values at each test point by evenly sampling backwards rays in all directions.

I've looked at this: https://www.radiance-online.org/community/workshops/2009-boston-ma/Presentations/rogers_SPOT%20on.pdf

However, I don't understand the sin/cosine parts and I am focused and radiometric units, not human-centered units like luminance.

Thank you!

Best,

Valerie