[Radiance-general] Re: Radiance-general Digest, Vol 59, Issue 8
Jack de Valpine
jedev at visarc.com
Thu Jan 15 18:07:06 PST 2009
Hi Galen,
No problem.
Regarding the header
* Rc<r,g,b> - these are the rgb components for the reflectance on
the "coated" side of the monolithic glass
* Rg<r,g,b> - these are the rgb components for the reflectance on
the non-coated side of the monolithic glass
* T<r,g,b> - these are the rgb components for the transmittance for
the monolithic glass
* Part - this is a boolean value
o 0 means this is a regular glass
o 1 means this is a frit - if this is the case the "coated"
side reflectance needs to represent the reflectance of the
frit at 100% coverage which should be possible to extract
from the glazing manufacturer
The RGB values are extracted from the file generated for a "radiance"
export from Optics. This should be for a single pane monolithic glass
description (not a multi-layer make-up). The file will have three
Radiance material definitions, the two BRDTfunc definitions are the ones
to pay attention to. The makeup is something like the following:
void BRTDfunc some.glass.front
10
Rfr Rfg Rfb
Tr Tg Tb
0 0 0
.
9 0 0 0 0 0 0 0 0 0
void BRTDfunc some.glass.back
10
Rbr Rbg Rbb
Tr Tg Tb
0 0 0
.
9 0 0 0 0 0 0 0 0 0
So you need to take the two rgb triples for reflectance and one for
transmittance. So an entry in the data file could look like this (you
will need to figure which represents the coated side if needed):
Surface Tr Tg Tb Rcr Rcg Rcb Rgr Rgg Rgb Part
<name> Tr Tg Tb Rfr Rfg Rfb Rbr Rbg Rbb 0
A file for a double pane insulating unit might look like the following:
Surface Tr Tg Tb Rcr Rcg Rcb Rgr Rgg Rgb Part
green-lowe Tr Tg Tb Rfr Rfg Rfb Rbr Rbg Rbb 0
The glaze script contains a default "clear" glass. I seem to recall that
this is required for the script to output a material description (eg it
must have a "clear" glass description"). If this is not suitable the
script requires some modification, which I think I can offer some
guidance on so that you can include your own "clear" glass description.
I would suggest before you do anything else you should test out the
script as is with the built in values. This will let you see how it
works. You will assign different materials to different layers to build
up the composite unit.
Try it out and let me know if you have more questions.
-Jack
Galen Burrell wrote:
> Jack,
> Thanks for the input and offer to answer a few questions. Much appreciated.
> I see the header information the glaze script is looking for the following when importing a data file:
>
> Surface Tr Tg Tb Rcr Rcg Rcb Rgr Rgg Rgb Part
>
>
> Questions:
> 1. Are the RGB values for T, Rc, Rg easily found in Optics 5? I selected 'Color - Transmittance' under Tools>Select Spectrum, and tried all the different wavelength functions, but I'm not seeing RGB anywhere.
> Am I missing something?
> 2. Between Rc and Rg, which one refers to outside surface?
> 3. What does 'Part' refer to in the header above?
> 4. For a double pane IGU with a low-e coating on green glass (surface 2), would the data file look something like this?
>
> Surface Tr Tg Tb Rcr Rcg Rcb Rgr Rgg Rgb Part
> 1 Trgb, Rrgb, Part information for green glass
> 2 Trgb, Rrgb, Part information for green glass + LowE coating (or would it be just the LowE coating?)
> 3 Trgb, Rrgb, Part information for clear glass
> 4 Trgb, Rrgb, Part information for clear glass
>
> Thanks for your time and assistance - much appreciated.
>
> Galen
>
> Message: 3
> Date: Wed, 14 Jan 2009 18:08:02 -0500
> From: Jack de Valpine <jedev at visarc.com>
> Subject: Re: [Radiance-general] Glazing transparency/reflectivity
> study
> To: Radiance general discussion <radiance-general at radiance-online.org>
> Message-ID: <496E7052.9020408 at visarc.com>
> Content-Type: text/plain; charset="iso-8859-1"
>
> Hi Galen,
>
> You should probably consider the glaze script to produce a material
> description for your glazing. I think that this will you get the most
> sophisticated description for a glass material. You can incorporate data
> that is output from Optics for single monolithic glass types to build up
> double pane insulating units if needed. A coating can be applied to a
> selected layer of the make-up. Note, that using the simple BRTDfunc
> description output from Optics (unless this has been updated in the past
> few years) does not account for variation due to incident angle. There
> is actually a way to set up the glaze script so it accepts a file of
> glass types as input rather than using the rather minimal inputs that
> come with script.
>
> Let me know if you have any questions and I will do the best I can to
> help out.
>
> -Jack
>
> Galen Burrell wrote:
>
>> I'm considering doing a study comparing the transparency (as viewed
>> from outside) of two glazing types on a building modeled in
>> radiance. The study would render several viewpoints (and view angles
>> looking up the facade) for the multiple glass types under a variety of
>> sky conditions (sunny, cloudy, etc). The primary goal of the study
>> would be to as follows:
>>
>> 1. Demonstrate how exterior transparency changes with different glass
>> types (with different coatings and exterior reflectances)
>> 2. Demonstrate how exterior transparency changes with angle of incidence
>> 3. Demonstrate how exterior transparency changes based on ratio of
>> interior to exterior illuminance (or more accurately, luminances).
>>
>> I'm only interested in this as a comparative study: does glass type A
>> look clearer than glass type B when viewed at X angle and under Y sky
>> condition, and Z interior/exterior illuminance ratio.
>>
>> My question to the list is:
>> 1. Comments on the usefulness of this study?
>> 2. Advantage of using Optics 5 rad file (BRTDfunc) over glass
>> primitive? My understanding is it more accurately captures the color
>> of the glass and reflectivity... anything else?
>>
>>
>> Thanks,
>> Galen
>>
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>
> --
> # Jack de Valpine
> # president
> #
> # visarc incorporated
> # http://www.visarc.com
> #
> # channeling technology for superior design and construction
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--
# Jack de Valpine
# president
#
# visarc incorporated
# http://www.visarc.com
#
# channeling technology for superior design and construction
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