[Radiance-general] BSDF orientation and implementation

Thu Feb 27 10:54:24 PST 2014

Chris,
A few weeks ago somebody alerted me to a bug in BSDFViewer for tensor tree
BSDFs that flips the transmission front and back. So your tensor tree BSDF
is probably fine. My stupid utility has a bug.  I'll let you know when I've
fixed it and posted a new version.
Andy

On Thu, Feb 27, 2014 at 6:43 AM, Chris Coulter <
Chris.Coulter at burohappold.com> wrote:

> Andy/David/Rob - Thanks for the encouragement and suggestions.
>
> I've been working through trying to troubleshoot as I go along. Studying
> it in a 10m cube so I can easily understand how the light is being
> redistributed rather than in my full model. I also found that running the
> CFS through genBSDF with an all black material helpful to digest that
> specular transmission is occurring as expected.
> Andy's reminder that +Z is "in" the space was helpful in making me
> understand why the Klems bsdf seemed backwards. Now my tensor tree bsdf
> seems backwards using the same geometry - which is unnerving. I'm reworking
> the process and will post updates, and inevitably more questions. I was
> finally able to get Andy's BSDF Viewer to compile in Ubuntu - it was much
> easier once I realized the network had been disabled and then resolved my
> proxy issues for the compiler's dependencies. I forgot about bsdf2rad, will
> look into it.
>
> David, your note was clear. Thanks. My system is grid a 10mm cubes fit
> into skylights that are 4m x 8m or larger. I think the edge condition can
> be ignored in the BSDF calculation.
>
>
> Thanks again all for help here and in the tutorials, presentations, code,
> etc. Once I can confirm my results are wrong and its not as much of a user
> error as it likely is, I'll post more info/questions.
>
> Chris
>
> -----Original Message-----
> From: Guglielmetti, Robert [mailto:Robert.Guglielmetti at nrel.gov]
> Sent: Wednesday, February 26, 2014 11:40 PM
> To: Radiance general discussion
> Subject: Re: [Radiance-general] BSDF orientation and implementation
>
> Hi Chris,
>
> What Andy said! To that end, I would add that tools like objview (for
> visualizing your CFS geometry) and bsdf2rad (for visualizing the BSDF
> distribution) are very useful for getting comfortable with your generated
> BSDFs. I am working on a little "test room" model, a la the ltview script
> but for CFS instead of luminaries. When it's sensible I'll post some
> results. It's very helpful to visualize these things; Andy's BSDFviewer is
> awesome, but I also like to mock these things up in Radiance proper so I am
> certain the functions and the models are are being implemented and oriented
> correctly, you know what I mean?
>
> - Rob
>
> From: David Geisler-Moroder <david.moroder at gmail.com<mailto:
> david.moroder at gmail.com>>
> Reply-To: Radiance discussion <radiance-general at radiance-online.org
> <mailto:radiance-general at radiance-online.org>>
> Date: Wednesday, February 26, 2014 at 10:34 AM
> To: Radiance discussion <radiance-general at radiance-online.org<mailto:
> radiance-general at radiance-online.org>>
> Subject: Re: [Radiance-general] BSDF orientation and implementation
>
> Hi Chris,
>
> a short note from my side:
> Yes, you can import BSDFs of systems into WINDOW and generate new BSDFs
> including the glass panes of your IGU. Therefore my approach is usually to
> simulate only the system without any glazing and put the overall system
> together in WINDOW with the right glass.
> Concerning the generation of BSDFs for various applications of a single
> system you should decide if the kind of system you are simulating is
> representative for your application. I tend to simulate typical periods of
> a systems (e.g. for a lamella system you can use the -dim settings to get
> that right) and model any frame in the geometric model. However, in cases
> where e.g. the ratio of system thickness to system size dimension is quite
> high and thus the frame will significantly influence the BSDF, it is better
> to include the real geometry in the BSDF simulation model. However, you
> then probably end up generating more than a single BSDF for the same system
> depending on the applications.
>
> I hope it's somehow clear... if not, let me know and I'll try again ;-)
>
> Cheers,
> David
>
>
>
> 2014-02-26 1:03 GMT+01:00 Andrew McNeil <amcneil at lbl.gov<mailto:
> amcneil at lbl.gov>>:
> Chris,
> Everything you write seems correct. One whatch-it I can offer is to make
> sure you're system is situated properly for the genBSDF run. +Z is into the
> space, +Y is up.  All of the geometry should be in the -Z space. If you
> don't follow these guidelines you're BSDF will be strange.
> Andy
>
>
> On Tue, Feb 25, 2014 at 8:06 AM, Chris Coulter <
> Chris.Coulter at burohappold.com<mailto:Chris.Coulter at burohappold.com>>
> wrote:
> Good morning Gurus!
>
> I have worked through the 3- and 5-phase tutorials in hopes of being able
> to apply a BSDF to one of my projects. This project will be using
> micro-louver cellular structures imbedded within an IGU, in both skylights
> and vertical windows. I think I understand the general process, but wanted
> to ask a few questions before getting too far down the road...
>
> The skylights and windows are all different sizes and the windows are in
> multiple orientations (of course). My understanding of the BSDF and
> seemingly from this mail (
> http://www.radiance-online.org/pipermail/radiance-general/2011-November/008248.html),
> I should be able to calculate the BSDF once for my system. I was planning
> model the louvers as 1m by 1m, but run genBSDF with the -dim arguments
> smaller than this. Is this the correct approach? Ideally I would not
> calculate the BSDF for each orientation, assuming that micro-louver
> geometry does not change.
>
> In my BSDF material definition, I would alter the up vector according to
> the surface being applied - the up vector matches the BSDF orientation
> (calculated in xy space) to the specific geometry's orientation (0 0 1 for
> a window). If the louver are rotated within the IGU assembly (rz -45) for a
> skylight, I can account for this with the up vector of 1 1 0 (surface
> normal is 0 0 1). This would hold true for rotation within the vertical
> apertures as well. Each different up vector would be a different BSDF
> material.
>
> Lastly, if the glazing properties (VLT) are not defined yet, can I import
> the BSDF file into Window and create multiple options for IGU's with
> varying properties? It seems so from David Geisler-Moroder's presentation
> at the 2012 Workshop (
> http://radiance-online.org/community/workshops/2012-copenhagen/Day1/Geisler-Moroder/geisler-moroder_BSDF_tutorial_s.pdf).
> Certainly skylights and windows will have different VLT and it would again
> be nice to not be required to run genBSDF multiple times.
>
> I am in the process of working through the steps on my own, but wanted to
> ask these questions while I'm waiting on genBSDF.
>
>
> Any help is much appreciated, as always.
>
> Chris Coulter
> Senior Lighting Designer
> Buro Happold Consulting Engineers
> 100 Broadway, 23rd Floor
> New York, NY 10005
> Tel: 212.334.2025<tel:212.334.2025>
> Direct: 212.616.0254<tel:212.616.0254>
> Email: chris.coulter at burohappold.com<mailto:chris.coulter at burohappold.com>
> Website: www.burohappold.com<http://www.burohappold.com>
>
>
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