Question-and-Answer Resource for the Building Energy Modeling Community
 | 1 | initial version |
Thank you so much, and sorry for the confusing explanation. In short, I want to create a system of horizontal-blinds where the material is a redirecting-daylighting-system (BSDF), I rephrase:
I used genblinds to create a shading system (horizontal blinds) but instead of using a uniform reflectance material (void plastic white), I'm using the BSDF of a daylighting-redirecting system (redirecting-system.xml - which was generated by a gonio-photometer). Since the position of the blinds is horizontal, I'm assuming that first I need to place the material (XML file of the redirecting-system) in an horizontal position (in the window-BSDF file: 0 1 0 .), then the tilt of the blinds (0°, 20°, 45°), would be specified by the genblind parameters' (this is just a test, so its pretty much like in the tutorial):
genblinds cfs blinds 2 400 4 4 45 |xform -rz -90 -rx -90 -t 0 0 -.939693 > sys/blindsRS45.rad
the genblinds RAD file (blindsRS45.rad) looks like this:
# xform -rz -90 -rx -90 -t 0 0 -.939693
# genblinds cfs blinds 2 400 4 4 45
void BSDF cfs
6 0 xml/redirecting-system.xml 0 1 0 .
0
0
Then I used such file to generate an XML file using genBSDF:
genBSDF +f +b -c 500 -geom inch -dim 199 201 1.5 2.5 -.939693 0 sys/blindsRS45.rad > sys/blindsRS45.xml
Then I used the resulting XML (blindsRS45.xml) file to create a window-system where the horizontal blinds (using the redirecting-system as material) are placed behind a vertical glass pane (in this case such glass material was included in the same window-BSDF file but I know I can also add it in Window-7), thus in the final RAD file (mywindowsystem.rad) the XML position is vertical: 0 0 1
##mywindowsystem.rad
void BSDF fenestration
6 0 sys/blindsRS45.xml 0 0 1 .
0
0
fenestration polygon window
0
0
12
10.000000 -0.010000 2.800000
My questions are, first if this approach is correct to simulate horizontal blinds using BSDF material, and then about the calculation of the interreflections occurring between the horizontal-slats, since I'm not using a diffuse uniform material (plastic) but a BSDF material, then I guess such calculation would be done using the transmission-reflection/back-front data of the XML file (incident and outgoing rays). I wonder if my understanding of this process is correct, then if the results might be at some extent inaccurate according to:
a) the following sentence in the 'Three Phase Method Tutorial' (pag. 4, 2.2 Transmission Matrix (BTDF):
'Currently, Radiance only uses the front transmission data, thus front and back reflection and back transmission are ignored by Radiance'.
b) the XML file of the original redirecting-daylighting-system was generated with a goniophotometer, where no back transmission and front and back reflection data was considered. (although the resulting BSDF-XML file contains all such data).
Hoping that my question is better described now, I thank you in advance.
Chantal.
| | 2 | No.2 Revision |
Thank you so much, and sorry for the confusing explanation. In short, I want to create a system of horizontal-blinds where the material is a redirecting-daylighting-system (BSDF), I rephrase:
I used genblinds to create a shading system (horizontal blinds) but instead of using a uniform reflectance material (void plastic white), I'm using the BSDF of a daylighting-redirecting system (redirecting-system.xml - which was generated by a gonio-photometer). Since the position of the blinds is horizontal, I'm assuming that first I need to place the material (XML file of the redirecting-system) in an horizontal position (in the window-BSDF file: 0 1 0 .), then the tilt of the blinds (0°, 20°, 45°), would be specified by the genblind parameters' (this is just a test, so its pretty much like in the tutorial):
genblinds cfs blinds 2 400 4 4 45 |xform -rz -90 -rx -90 -t 0 0 -.939693 > sys/blindsRS45.rad
the genblinds RAD file (blindsRS45.rad) looks like this:
# xform -rz -90 -rx -90 -t 0 0 -.939693
# genblinds cfs blinds 2 400 4 4 45
void BSDF cfs
6 0 xml/redirecting-system.xml 0 1 0 .
0
0
Then I used such file to generate an XML file using genBSDF:
genBSDF +f +b -c 500 -geom inch -dim 199 201 1.5 2.5 -.939693 0 sys/blindsRS45.rad > sys/blindsRS45.xml
Then I used the resulting XML (blindsRS45.xml) file to create a window-system where the horizontal blinds (using the redirecting-system as material) are placed behind a vertical glass pane (in this case such glass material was included in the same window-BSDF file but I know I can also add it in Window-7), thus in the final RAD file (mywindowsystem.rad) the XML position is vertical: 0 0 1
##mywindowsystem.rad
void BSDF fenestration
6 0 sys/blindsRS45.xml 0 0 1 .
0
0
fenestration polygon window
0
0
12
10.000000 -0.010000 2.800000
My questions are, first if this approach is correct to simulate horizontal blinds using BSDF material, and then about the calculation of the interreflections occurring between the horizontal-slats, since I'm not using a diffuse uniform material (plastic) but a BSDF material, then I guess such calculation would be done using the transmission-reflection/back-front data of the XML file (incident and outgoing rays). I wonder if my understanding of this process is correct, then if the results might be at some extent inaccurate according to:
a) the following sentence in the 'Three Phase Method Tutorial' (pag. 4, 2.2 Transmission Matrix (BTDF):
'Currently, Radiance only uses the front transmission data, thus front and back reflection and back transmission are ignored by Radiance'.
b) the XML file of the original redirecting-daylighting-system was generated with a goniophotometer, where no back transmission and front and back reflection data was considered. (although the resulting BSDF-XML file contains all such data).
Hoping that my question is better described now, I thank you in advance.
Chantal.
