translucent panel ( trans material )

Hello Everyone,

I know characteristics of a 4mm thick translucent panel (measured with a spectrophotometer). I try to introduce it in RADIANCE.

Measurements on the exterior side (glossy) give :

Transmittance_diffuse = 75.5% and transmittance_spec = 9.1%

Reflectance_diffuse = 7.7%

Absorptance = 7.8%

Measurements on the interior side (mat) give :

Transmittance_diffuse = 81.6% and transmittance_spec = 8.9%

Reflectance_diffuse = 7.8%

Absorptance = 1.6%

I’m not sure that I introduced it in RADIANCE in a correct way …

(following formulas p325 in Rendering with Radiance)

void trans vitr_dif

0

0

7 0.71 0.77 0.77 0 0.1 0.99 0.0012

With

Cr = 0.074

Cg = 0.08

Cb = 0.08

Rd = 0.265*Cr+0.67*Cg+0.065*Cb = 0.07841

Rs = 0

Sr = 0.1

Td = 75.5

Ts = 0.091

Thank you for your help !

Coralie

···

-----------------------------------------------------------------------------------------
Coralie Cauwerts

Researcher

Université catholique de Louvain

Belgium

Dear Coralie

if you have the full spectro-data, there may be a different path: There is a tool called “glaze” (a script found in the standard radiance installation). With this script, you can convert Optics (“Optics” being the freeware program from the LBNL) spectral data into a more detailed Radiance description (type “BRTDfunc”) by exporting from Optics in “Radiance Format” and then entering this data in the “glaze” script.

I am laboring under the possible delusion that this is generally a better description for “advanced” glazing products (and possibly any translucent materials). However, I am quite new at this.

Regards

Achim

···

From: [email protected] [mailto:[email protected]] On Behalf Of Coralie Cauwerts
Sent: Donnerstag, 17. Dezember 2009 11:01
To: [email protected]
Subject: [Radiance-general] translucent panel ( trans material )

Hello Everyone,

I know characteristics of a 4mm thick translucent panel (measured with a spectrophotometer). I try to introduce it in RADIANCE.

Measurements on the exterior side (glossy) give :

Transmittance_diffuse = 75.5% and transmittance_spec = 9.1%

Reflectance_diffuse = 7.7%

Absorptance = 7.8%

Measurements on the interior side (mat) give :

Transmittance_diffuse = 81.6% and transmittance_spec = 8.9%

Reflectance_diffuse = 7.8%

Absorptance = 1.6%

I’m not sure that I introduced it in RADIANCE in a correct way …

(following formulas p325 in Rendering with Radiance)

void trans vitr_dif

0

0

7 0.71 0.77 0.77 0 0.1 0.99 0.0012

With

Cr = 0.074

Cg = 0.08

Cb = 0.08

Rd = 0.265*Cr+0.67*Cg+0.065*Cb = 0.07841

Rs = 0

Sr = 0.1

Td = 75.5

Ts = 0.091

Thank you for your help !

Coralie

-----------------------------------------------------------------------------------------
Coralie Cauwerts

Researcher

Université catholique de Louvain

Belgium

Hi Coralie and Achim,

A couple of comments. Optics 5 models thermal and spectral optical properties of a wide range of glazing based on measured data. However it does not contain a model for for diffusely transmitting materials. So for modeling complex glazing systems and exporting data for use in the "glaze" script it is a great place to start, however it will not help with the kind of data that it looks like Coralie has available, which suggests a material with a large diffuse transmitting component.

There are a few things to note about the information that Coralie provided. One is that it looks like one side is "shiny" or specular while the other is "mat" or diffuse. The trans material will not give you control over what happens on each side of the material. Based on this alone it is likely that this is a material that would be better characterized using the BRTDfunc material type. This allows for more flexibility in describing material behavior. However, this being said there is one thing that is a little puzzling (there are others who may chime in on this who know more), this is that your measurments show different transmittance (total) depending on the side of the material. Is this possible? This certainly cannot be modeled with the "trans" material type.

Regards,

-Jack de Valpine

···

--
# Jack de Valpine
# president
#
# visarc incorporated
# http://www.visarc.com
#
# channeling technology for superior design and construction

Achim Geissler wrote:

Dear Coralie

if you have the full spectro-data, there may be a different path: There is a tool called “glaze” (a script found in the standard radiance installation). With this script, you can convert Optics (“Optics” being the freeware program from the LBNL) spectral data into a more detailed Radiance description (type “BRTDfunc”) by exporting from Optics in “Radiance Format” and then entering this data in the “glaze” script.

I am laboring under the possible delusion that this is generally a better description for “advanced” glazing products (and possibly any translucent materials). However, I am quite new at this.

Regards

Achim

*From:* [email protected] [mailto:[email protected]] *On Behalf Of *Coralie Cauwerts
*Sent:* Donnerstag, 17. Dezember 2009 11:01
*To:* [email protected]
*Subject:* [Radiance-general] translucent panel ( trans material )

Hello Everyone,

I know characteristics of a 4mm thick translucent panel (measured with a spectrophotometer). I try to introduce it in RADIANCE.

Measurements on the exterior side (glossy) give :

Transmittance_diffuse = 75.5% and transmittance_spec = 9.1%

Reflectance_diffuse = 7.7%

Absorptance = 7.8%

Measurements on the interior side (mat) give :

Transmittance_diffuse = 81.6% and transmittance_spec = 8.9%

Reflectance_diffuse = 7.8%

Absorptance = 1.6%

I’m not sure that I introduced it in RADIANCE in a correct way …

(following formulas p325 in Rendering with Radiance)

void trans vitr_dif

0

0

7 0.71 0.77 0.77 0 0.1 0.99 0.0012

With

Cr = 0.074

Cg = 0.08

Cb = 0.08

Rd = 0.265*Cr+0.67*Cg+0.065*Cb = 0.07841

Rs = 0

Sr = 0.1

Td = 75.5

Ts = 0.091

Thank you for your help !

Coralie

*-----------------------------------------------------------------------------------------
*Coralie Cauwerts

Researcher

Université catholique de Louvain

Belgium

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

_______________________________________________
Radiance-general mailing list
[email protected]
http://www.radiance-online.org/mailman/listinfo/radiance-general

Hi Coralie,

I was thinking the same thing as Jack, is it possible to have different
transmission for each side? And even more puzzling, is it possible for a
substance to absorb five times more light in one direction compared to the
other? Perhaps you could tell us how these values were measured?

Using your values for the exterior side I get the following trans definition
(including sr=0.1):

void trans transmat
0
0
7 0.887 0.959 0.959 0.000 0.100 0.917 0.108

If you change your Td from 75.5 to 0.755 I think your results will agree
with mine.

Using your values for the interior side I get a trans definition with values
for A2 and A3 that are out of range, so something isn't quite right. Again
I think we could help if your shared your method for measuring your
translucent panel.

Best,
Andrew

···

On 12/17/09 6:08 AM, "Jack de Valpine" <[email protected]> wrote:

Hi Coralie and Achim,

A couple of comments. Optics 5 models thermal and spectral optical
properties of a wide range of glazing based on measured data. However it
does not contain a model for for diffusely transmitting materials. So
for modeling complex glazing systems and exporting data for use in the
"glaze" script it is a great place to start, however it will not help
with the kind of data that it looks like Coralie has available, which
suggests a material with a large diffuse transmitting component.

There are a few things to note about the information that Coralie
provided. One is that it looks like one side is "shiny" or specular
while the other is "mat" or diffuse. The trans material will not give
you control over what happens on each side of the material. Based on
this alone it is likely that this is a material that would be better
characterized using the BRTDfunc material type. This allows for more
flexibility in describing material behavior. However, this being said
there is one thing that is a little puzzling (there are others who may
chime in on this who know more), this is that your measurments show
different transmittance (total) depending on the side of the material.
Is this possible? This certainly cannot be modeled with the "trans"
material type.

Regards,

-Jack de Valpine

____________________________________________________________
Electronic mail messages entering and leaving Arup business
systems are scanned for acceptability of content and viruses

···

From: [email protected]
To: [email protected]
Sent: Thu Dec 17 05:00:32 2009
Subject: [Radiance-general] translucent panel ( trans material )

Hello Everyone,

I know characteristics of a 4mm thick translucent panel (measured with a spectrophotometer). I try to introduce it in RADIANCE.

Measurements on the exterior side (glossy) give :

Transmittance_diffuse = 75.5% and transmittance_spec = 9.1%

Reflectance_diffuse = 7.7%

Absorptance = 7.8%

Measurements on the interior side (mat) give :

Transmittance_diffuse = 81.6% and transmittance_spec = 8.9%

Reflectance_diffuse = 7.8%

Absorptance = 1.6%

I’m not sure that I introduced it in RADIANCE in a correct way …

(following formulas p325 in Rendering with Radiance)

void trans vitr_dif

0

0

7 0.71 0.77 0.77 0 0.1 0.99 0.0012

With

Cr = 0.074

Cg = 0.08

Cb = 0.08

Rd = 0.265Cr+0.67Cg+0.065*Cb = 0.07841

Rs = 0

Sr = 0.1

Td = 75.5

Ts = 0.091

Thank you for your help !

Coralie

**-----------------------------------------------------------------------------------------
**Coralie Cauwerts

Researcher

Université catholique de Louvain

Belgium

Hi all,

Thanks for your responses.

Values were measured with a spectrophotometer UV-VIS-NIR. The reference is a
spectralon. I know that measurements are only indicative because some errors
can occur when diffuse material is measured with this kind of method but I
have no other source of information about the material.

In my model, only the “interior side” of the glass is visible.

Andrew, I agree with your correction, I saw my mistake yesterday

Coralie

···

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

Coralie Cauwerts

Researcher

Université catholique de Louvain

Belgium

Hi Coralie,

I¹m not familiar with Spectralon or if there are different varieties of
spectralon, but all the hits of my quick search reveals a substance with
high diffuse reflectance. And your measurements suggest high diffuse
transmission. Is it possible that you are confusing Td with Rd? That would
explain concerns regarding inconsistent transmission values for front and
back.

After talking with a materials guy, I now know that it is possible for a
composite material to have different absorbance depending on direction of
travel (ie if you have a silver coating on one side of glass, light from one
side will pass through the glass twice while light from the other side may
not pass through the material at all). So for me that is no longer a
puzzle.

Andy

···

On 12/18/09 9:45 AM, "Coralie Cauwerts" <[email protected]> wrote:

Hi all,

Thanks for your responses.
Values were measured with a spectrophotometer UV-VIS-NIR. The reference is a
spectralon. I know that measurements are only indicative because some errors
can occur when diffuse material is measured with this kind of method but I
have no other source of information about the material.
In my model, only the ³interior side² of the glass is visible.
Andrew, I agree with your correction, I saw my mistake yesterday Š

Coralie
------------------------------------------------------------------------------
-----------
Coralie Cauwerts
Researcher
Université catholique de Louvain
Belgium

_______________________________________________
Radiance-general mailing list
[email protected]
http://www.radiance-online.org/mailman/listinfo/radiance-general

____________________________________________________________
Electronic mail messages entering and leaving Arup business
systems are scanned for acceptability of content and viruses