[Radiance-general] 5Phase & proxy geometry

[Andrew McNeil]

Hi Chantal,

1.- I’m not sure of the use of the ‘BSDFproxy polygon inside’ included in
> the glazing_bsdf.rad file.
>
The BSDF material is applied to this surface. It allows Radiance to use the
BSDF data in lieu of sampling the geometry during the direct sun simulation.


> If the latter was generated by genBSDF and includes already the dimensions
> of the venetian blind, the model, the glazing, and the thickness is also
> specified…why do we need to specify the coordinates of the polygon (same of
> the glow material) in this file?
>
The BSDF is not always produced by genBSDF, it can come from WINDOW or from
measurement as well. But regardless, the intention is that optical data in
a BSDF file is not specific to a size of window, and so you could use it in
various sized windows.  For example if lightlouver produces a BSDF for
their product using genBSDF for one project you might want to use it in a
2m window for one project but a 3m window for another. Addtionally there
may be times when you want to use a different thinckness for the
simulation.  I can think of probably half a dozen reasons why you might not
want to use dimensions baked into a BSDF file, an as is typical with
Radiance we lean towards generalization.


>
>
> I also wonder if we need to use proxy when only if we have a system such
> as venetian blinds. Is possible to use it also if we have a daylight system
> as thick as a glass pane such as lasercut panel 6mm?
>
Yes, but it isn't worth it unless you have a good Radiance material model
for the lasercut panel.  Otherwise you're better off using the BSDF
(assuming it was measured).


>
>
> I guess that I can shorten this question by: what would be exactly the
> function of the proxy geometry?
>
The BSDF, even high resolution tensortree BSDFs, are spatially averaged.  A
venetian blind that is angled to admit stripes of light modeled with only a
BSDF will result in a rectangular patch of intermediate brightness.  Using
proxy geometry results in bright sun alternating with dark shadows.

>
>
> 2.- Regarding this, in the tutorial you have to rotate the geometry in
> order to generate the two xml files (section 6.2) my
> silly-silly-super-silly question is:  what would be the orientation of
> the resulting xml file? Are we re-orientating it by the last three values
> of the orientation vector in the glazing_bsdf.rad ?
>
The WINDOW XML file standard says inside is +Z outside is -Z, up is +Y.
In Radiance we use up as +Z and inside and outside, well it depends on the
space your modeling.


>
>
> 3.- I have a final question that just came now when trying the 5Phase:
> What would be the number to use in rcontrib –bn when creating the
> direct-sun-coefficient-matrix?
>
> As I understand, it represents the number of sky patches, and it will
> generate the values of the RGB in the output file. But, if I use –e MF:6 –f
> reinhart.cal –b 5186, I obtain a matrix result with 31116 columns, which is
> the number of sky patches six times? Please tell me where am I wrong.
>

There should be three values per skypatch (R G and B) I don't know why you
are getting twice as many.  Can you send the full command you are using?

Andy
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