Hi,

In your example, you test the irradiance at a single point in *only one

direction* (up) which is not what I am trying to do unfortunately. If I

want to calculate the energy arriving at a point on a plane, calculating

irradiance from a single direction isn't realistic. Thus, I asked about

RSENSOR which you recommended that I use a long time ago. I am thinking

that for each point, I call RTRACE with the view direction -vd changing in

equal increments and then add the irradiances. For example, the view

directions for a very rough calculation would be in spherical

coordinates/degrees: (1, 0, 0), (1, 90, 0), (1, 180, 0), (1, 270, 0), (1,

0, 45), (1, 90, 45), (1, 180, 45), (1, 270, 45), (1, 0, 90).

Also, I am confused about "a list of RGB irradiance values (watts/sr/m^2)."

This looks like radiance, and reputable sources state that the units for

irradiance are (W/m^2).

Thank you!

Best,

Valerie

## ···

On Dec 28, 2017 3:00 PM, <[email protected]> wrote:

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Today's Topics:

1. RSENSOR questions (Valerie Tan)

2. Re: RSENSOR questions ([email protected])

3. Re: RSENSOR questions (Greg Ward)

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Message: 1

Date: Thu, 28 Dec 2017 12:17:49 -0500

From: Valerie Tan <[email protected]>

To: [email protected]

Subject: [Radiance-general] RSENSOR questions

Message-ID:

<CAFWG2TdKo8m2nbA5qfEG-pZRJawA7uBYM9YXyFDV8REGKwLeCA@mail.gmail.com>

Content-Type: text/plain; charset="utf-8"

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-bos

ton-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

--

Valerie Tan

Computer Science

College of Engineering

Cornell University '19

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Message: 2

Date: Thu, 28 Dec 2017 18:24:05 +0100 (CET)

From: [email protected]

To: [email protected]

Subject: Re: [Radiance-general] RSENSOR questions

Message-ID: <[email protected]>

Content-Type: text/plain; charset="UTF-8"

Bonjour,

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

En cas d'urgence, vous pouvez toujours appeler le num?ro g?n?ral d'Estia : +41

(0) 21/510.59.59 ou envoyer un mail ? l'adresse [email protected].

Pour toutes questions relatives ? DIAL+, merci d'utiliser l'adresse mail

[email protected].

Cordialement

Julien Boutillier

Estia SA

------------------------------

Message: 3

Date: Thu, 28 Dec 2017 09:48:34 -0800

From: Greg Ward <[email protected]>

To: Radiance general discussion <[email protected]>

Subject: Re: [Radiance-general] RSENSOR questions

Message-ID: <[email protected]>

Content-Type: text/plain; charset="us-ascii"

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 PSTHello,

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.or

g/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

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