[Radiance-general] Help on BRTDfunc
Jack de Valpine
jedev at visarc.com
Mon Oct 5 05:50:50 PDT 2009
Hi Jun and Erik,
To clarify a bit. The radiance material descriptions exported from
Optics 5 are as follows:
* front side as BRTDfunc
* back side as BRTDfunc
* glass
The front and back descriptions use a simple version of BRTDfunc, simple
in that they do not call any functions for additional calculations that
would help account for angular dependencies for transmittance and
reflectance. However they do start to capture higher reflectance
qualities of certain types of glass. The glass material will account for
the transmittance (transmissivity) of the material but will not account
for higher reflectances and differing front and backside reflectances.
BRTDfunc is a full material in Radiance, thus like a glass, plastic,
metal, etc material type, it can be applied directly to geometry. The
downside of the BRTDfunc descriptions exported from Optics is that they
do not account for angular dependencies found in glazing materials for
reflectance and transmittance, to do this you need to do a bit more
conversion. To have a material description that integrates both front
and back side characteristics as well as accounts for angular
dependencies, there are two ways to go:
1. optics2rad - converts the radiance format file output from optics
to a more robust BRTDfunc material description.
2. glaze - look at the glaze script for building up material
descriptions for different types of glass. Note that this can be
modified to include data for other glass types that you may export
from Optics (these must be exported as single layers, not composites).
Hope this helps.
-Jack de Valpine
Edilberto Calixihan wrote:
>
> Hello Erik,
>
>
>
> Actually your reply was very helpful. It pointed me to where else to
> look and think that BRTDfunc may be enough of a description.
>
>
>
> My rendered picture looks the same as using the "glass" material
> though, and it looks like I did not capture the glass reflectivity
> well. Anymore help is very very welcome.
>
>
>
> Cheers!
>
>
>
> Best regards,
>
> Jun
>
>
>
> *From:* Erik Moore [mailto:Erik.Moore at arup.com]
> *Sent:* Monday, October 05, 2009 6:36 PM
> *To:* jcalixihan at cladding.com; Radiance general discussion
> *Subject:* RE: [Radiance-general] Help on BRTDfunc
>
>
>
> yeup, your correct. I should have had a bit more of a look before my
> responce. As I previously said, I've never used the BRTDfunc material
> type so I'm afraid I'm not any help with the use of the funcfile??
>
>
>
> Anyone else?
>
>
>
> ------------------------------------------------------------------------
>
> *From:* radiance-general-bounces at radiance-online.org
> [mailto:radiance-general-bounces at radiance-online.org] *On Behalf Of
> *Edilberto Calixihan
> *Sent:* 05 October 2009 11:16
> *To:* 'Radiance general discussion'
> *Subject:* RE: [Radiance-general] Help on BRTDfunc
>
> Hi Erik,
>
>
>
> Thanks for giving some ideas on this and pointing in the right
> direction. I was already stuck.
>
>
>
> It seems BRTDfunc is already a material and we may not need the glass
> material definition anymore (pls. correct me here).
>
>
>
> Also it may seem that we may need to add the use of glazing.cal as
> mentioned in
> http://finance.dir.groups.yahoo.com/group/DesktopRadiance/message/14.
> I tried the below definition and it worked. Although I'm still not
> sure if this is the correct way. Any additional clues is highly welcome.
>
>
>
> void BRTDfunc Clear
>
> 10
>
> 0.077 0.082 0.082
>
> 0.857 0.894 0.877
>
> 0 0 0
>
> glazing.cal
>
> 0
>
> 9 0 0 0 0 0 0 0 0 0
>
>
>
>
>
> You're right on the same numbers of front and back reflectance from
> Optics 5 .rad file and will need to check the glass. I think Optics 5
> may have a bug on Radiance export but will verify:
> http://www.radiance-online.org/radiance-workshop5/2006_Radiance_Workshop/Presentations/Ward_RadianceFeatures.pdf
>
>
>
> Thanks and best regards,
>
> Jun
>
>
>
>
>
> *From:* Erik Moore [mailto:Erik.Moore at arup.com]
> *Sent:* Monday, October 05, 2009 4:47 PM
> *To:* jcalixihan at cladding.com; Radiance general discussion
> *Subject:* RE: [Radiance-general] Help on BRTDfunc
>
>
>
> Hi there Jun,
>
>
>
> I'm not an expert and I'm sure that someone might correct me but....
> you need to apply the modifier that you are using to the glass
> description. the term 'void' means that you are not applying a
> modifier. Also, you will need to change the name of the modifier (or
> the name of the polygons) as I think that your polygons have been
> named 'clear'.
>
>
>
> Try this:
>
>
>
> void BRTDfunc 01_Clear_8_front
>
> 10
>
> 0.077 0.082 0.082
>
> 0.857 0.894 0.877
>
> 0 0 0
>
> .
>
> 0
>
> 9 0 0 0 0 0 0 0 0 0
>
>
>
> 01_Clear_8_front glass clear
>
> 0
>
> 0
>
> 3 0.934 0.974 0.955
>
>
>
> Please note the order.... Radiance will need to read what the modifier
> is BEFORE it can be applied to anything. I have never used this sort
> of modifier before, so I'm not too sure on what the arguments are (and
> hence can't comment on them..??) and I'm not too sure why you have two
> of them (front and back) which are identical?
>
>
>
> hope this helps. Anyone else who can correct me on anything please but in!
>
>
>
> Erik
>
>
>
>
>
>
>
> ------------------------------------------------------------------------
>
> *From:* radiance-general-bounces at radiance-online.org
> [mailto:radiance-general-bounces at radiance-online.org] *On Behalf Of
> *Edilberto Calixihan
> *Sent:* 05 October 2009 08:21
> *To:* radiance-general at radiance-online.org
> *Subject:* [Radiance-general] Help on BRTDfunc
>
> Hello!
>
>
>
> I'm new to Desktop Radiance and use Ecotect to create and run the
> simulations. I need advise on using BRTDfunc. Below is the .rad file
> from Optics 5 for the clear glass that I need:
>
>
>
> void glass 01_Clear_8_glass
>
> 0
>
> 0
>
> 3 0.934 0.974 0.955
>
>
>
> void BRTDfunc 01_Clear_8_front
>
> 10
>
> 0.077 0.082 0.082
>
> 0.857 0.894 0.877
>
> 0 0 0
>
> .
>
> 0
>
> 9 0 0 0 0 0 0 0 0 0
>
>
>
> void BRTDfunc 01_Clear_8_back
>
> 10
>
> 0.077 0.082 0.082
>
> 0.857 0.894 0.877
>
> 0 0 0
>
> .
>
> 0
>
> 9 0 0 0 0 0 0 0 0 0
>
>
>
>
>
> When I insert it into the my scene file (replace the default glass
> command lines) I get an "unidentified modifier "Clear"" error. Which
> means the polygons referencing "Clear" cannot find the glass
> description, right? I would modify the glass description to various
> id combinations like the one below but I get a "bad arguments for
> "Clear"" error.
>
>
>
> void glass Clear Clear_8_glass
>
> 0
>
> 0
>
> 3 0.934 0.974 0.955
>
>
>
> void BRTDfunc Clear_8_front
>
> 10
>
> 0.077 0.082 0.082
>
> 0.857 0.894 0.877
>
> 0 0 0
>
> .
>
> 0
>
> 9 0 0 0 0 0 0 0 0 0
>
>
>
> void BRTDfunc Clear_8_back
>
> 10
>
> 0.077 0.082 0.082
>
> 0.857 0.894 0.877
>
> 0 0 0
>
> .
>
> 0
>
> 9 0 0 0 0 0 0 0 0 0
>
>
>
>
>
> How can I properly run BRTDfunc and the glass reflection numbers from
> Optics 5?
>
>
>
> The one that seems to run ok is below but not sure if I got it
> right.. Also, we don't have a Unix pc at work but I'm interested in
> the newer versions of Radiance. Shall I start to learn Cygwin or
> MinGW to access advance glass functions? Any advice would be very
> helpful.
>
>
>
> void glass Clear
>
> 0
>
> 0
>
> 3 0.934 0.974 0.955
>
>
>
>
>
> void BRTDfunc Clear_8_front
>
> 10
>
> 0.077 0.082 0.082
>
> 0.857 0.894 0.877
>
> 0 0 0
>
> .
>
> 0
>
> 9 0 0 0 0 0 0 0 0 0
>
>
>
> void BRTDfunc Clear_8_back
>
> 10
>
> 0.077 0.082 0.082
>
> 0.857 0.894 0.877
>
> 0 0 0
>
> .
>
> 0
>
> 9 0 0 0 0 0 0 0 0 0
>
>
>
>
>
>
>
> Thanks so much!
>
> Jun
>
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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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