Custom BSDF file script

answered 2016-11-15 11:38:40 -0500

rpg777
6960 ●6 ●15 http://openstudio.net/

Yes! This is cool, good on ya for taking this on. You are correct, the BSDF assignments (and the control algorithms) are hard coded into the Radiance forward translation step. This was in the interest of expedience, as we did not have time to build the interface required to facilitate user-specified BSDFs. There is a very basic mapping done, based on the shading control chosen by the user, here in WindowGroup.cpp.

The easiest way to use your own BSDFs would be to add a loop that rewrites mapping.rad sometime after the translation but before all the Radiance simulation crap happens. Actually I'd just do it right before calculateDaylightCoeffecients. Were you to embark on this today, I'd recommend you just hack this, and simply rewrite mapping.rad using full path(s) to the BSDF(s) you want to use. OpenStudio 2.0's API will have much better support for accessing files and assigning and referencing them in measures. At that point, I think the right answer would be to change the measure interface to allow users to specify the BSDFs in the GUI.

Speaking of hacks, you had also asked about the purpose of the air.bsdf file in your earlier comment. This is basically a unit matrix that passes all the flux through the window interface, unaltered. It's used for calculating the illuminance for a window group's "shades up" condition. This way we only have to compute one 3-phase pair of daylight coefficients per (shaded) window group. We sacrifice a bit of accuracy (the perfectly specular transmission is being smeared out to the 145 Klems hemispherical subdivisions) in the interest of speed and conservation of disk space. For windows with no shades, we simply do a "single phase" daylight coefficient calc for flux at the points of interest (with the actual glazing in the windows). The best solution for shaded windows is to use the 5-phase methodology but that comes with its own issues and challenges in the context of a GUI and what we were trying (and funded) to do. So, the basic workflow is dumbed down a bit and it is what it is. The beauty is it's all there in the repository and you are welcome to improve it. I look forward to seeing what you come up with! Please let us know if you have more questions as you get into it.

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Thanks Mr. Keitel. This is very very helpful and I will keep you informed of the progress (and problems of course)...more to come.

Determinant ( 2016-11-15 18:05:02 -0500 )edit

+1 for "Mr. Keitel".

rpg777 ( 2016-11-16 16:09:15 -0500 )edit

That was my rationale for the +1. What happens when you change your photo, though?

__AmirRoth__ ( 2016-11-16 16:37:18 -0500 )edit

Determinant is a very strong name, also. Very matrix-y.

__AmirRoth__ ( 2016-11-16 16:38:15 -0500 )edit

How close is the 5-phase implementation? Also, one of the measures I'm exploring will be automated shades, so it would be nice to have windows partially covered...is this possible with these tools? feature coming soon?

Determinant ( 2016-12-14 18:45:39 -0500 )edit

Five-phase in OpenStudio? That is not close at all; that work is not started, nor is it funded. Partially-covered windows are possible now, but you'd have to subdivide the window into as many discrete steps as you wanted for the shades to be deployed. Then you'd simply have a separate shading control on each slice of window. The sensor is automatically placed at the center of the largest polygon in a given window group, so bear that in mind. You could also have different setpoints for each window portion's control, which could be fun.

rpg777 ( 2016-12-15 13:26:32 -0500 )edit

Also keep in mind that if you finely subdivide the window you will create exponential growth in the number of datasets and thus the amount of time for the calculations and storage required.

rpg777 ( 2016-12-15 13:28:05 -0500 )edit

Thanks. So as I understand it. You mean to create a separate window for each step of closed blind, then control those as you would any other. My next questions: I'm also looking at electrochromics. Any hints on how I might approach modifying this? I'd like to change OS/Radiance's built-in on/off transmittance. Also, is the DGP in OS the enhanced simplified or just simplified?

Let me know if my questions warrant a different format than this forum.

Determinant ( 2016-12-27 16:57:29 -0500 )edit

Also, what adaptive angles are chosen when "Number of Daylighting Views" is incremented? How can I access this in OS (i.e. not in the Sketchup plugin)?

Determinant ( 2016-12-27 17:15:18 -0500 )edit

I think it would be more helpful if these last two comments were re-posted as actual questions...

rpg777 ( 2017-01-09 12:05:16 -0500 )edit

Got it. Some of this just got put on hold so will post if/when it becomes relevant again. In the meanwhile have other question(s) that I will post.

Determinant ( 2017-01-09 14:23:06 -0500 )edit

Hi, I'm joining this conversation as my question is related. These replies are from one year ago, so I'm asking for an update: is the use of custom user defined BSDF (created with LBNL-WINDOW or genBSDF) already implemented in Open Studio? And also any hint of the possibility of image generation for dynamic glare analysis (sorry if I'm out-of-date, I stopped using OS for a while), thank you!