[Radiance-general] Radiance-general Digest, Vol 122, Issue 28

Fri Apr 25 06:09:50 PDT 2014

Thanks, Chris.
/Anne

On Tue, Apr 22, 2014 at 8:15 PM, <
radiance-general-request at radiance-online.org> wrote:

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> Today's Topics:
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>    1. Re: Fwd: How to interpret the -vu for genklemsamp ?
>       (Chris Coulter)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Tue, 22 Apr 2014 18:15:39 +0000
> From: Chris Coulter <Chris.Coulter at BuroHappold.com>
> To: Radiance general discussion <radiance-general at radiance-online.org>
> Subject: Re: [Radiance-general] Fwd: How to interpret the -vu for
>         genklemsamp ?
> Message-ID:
>         <CBDA7B0F3FC5354F986B71977E204BEC212FF45E at EX-MBX01.burohappold.com
> >
> Content-Type: text/plain; charset="utf-8"
>
> Anne,
>
> Yes, your situation seems quite complicated (or maybe just confusing). I
> had enough troubles visualizing without the added roatations you have. It
> seems as if you understand the basics, the view up vector correctly
> aligns/rotates your BSDF (about the normal vector) to the geometry in your
> model.
> If your vector math is correct for the rotations you?ve noted below, I
> would have expected a kbin of (-0.09,0.26,1,-0.82,0,0.57). I also would
> have expected the vu vector to have non-zero components for Y. My
> understanding of order of operations would be: rotate BSDF 55d on a flat
> plane, then orient that vu to your real-world geometry. The base BSDF is
> oriented in XY, with +Y being the vu vector. Andy?s note the other day on
> rotation got me to full visualize having to orient both view and daylight
> matrices to the xml file. Think of them as hemispheres (or your cupped
> hands) about the geometry of the bsdf?
>
> I might suggest a few things:
>
> 1)     if you have access to a CAD/modelling software, it is probably
> worthwhile taking some simple geometry with a line for the normal vector
> and one for the vu vector as it is aligned to your BSDF (assuming +Z is
> into room, +Y is ?up?, geometry lives in ?Z space). Then, begin the
> necessary rotations required to properly orient the geometry to what is in
> your model. Query the normal and view up vectors and there you have it.
>
> 2)     I also find extremely helpful is physically rotating something on
> your desk w/ some indicating lines on it to better visualize things. I grab
> a pack of gum, my phone, post-it notes, etc and hold a pen in the vu vector
> and start spinning it around to understand at least what quadrants the
> vectors should lie in. While this won?t give you the vector components,
> this at least helps understand the relative rotations.
>
> 3)     If your BSDF is quite complex and you?re not sure how it should
> behave, you might try to substitute with a simple blind/slat system that
> obscures a known set of sun positions. This also helped me in verifying
> that the rotations seemed correct before inserting the more complex BSDF.
>
> Good luck!
>
> Chris
>
>
> From: Anne Iversen [mailto:iversen.anne at gmail.com]
> Sent: Tuesday, April 22, 2014 9:38 AM
> To: radiance-general
> Subject: [Radiance-general] Fwd: How to interpret the -vu for genklemsamp ?
>
> Hello list,
> I have a question related to Chris Coulters question about BSDF
> orientation and implementation earlier this month.
> I have a BSDF, placed in a skylight, with normal vector, vp of: -0.09 0.26
> 1 (The skylights are oriented counterclockwise 335?N, and with tilt of 15?).
>
> Now I come to the more tricky part ? at least for me ? considering the
> ?view up?:
> The clockwise rotation of the BSDF in the plane of the glass is 55?.
> The default vu is 0 0 1. Doing some right-hand gymnastics, the coordinate
> system of the BSDF-plane is translated as the (x,z) coordinate system with
> the ?top? of the default-BSDF in 0 0 1 ?. Since the BSDF I?m about to
> simulate is oriented 55? clockwise in this coordinate system my ?vu vector
> will be (-0.82 0 0.57). The kbin for my view matrix then turns into
> kbin(-0.0936,0,0.2578,-0.82,0,0.57). I have tried to sketch this on a very
> simple hand drawing located here:
> https://dl.dropboxusercontent.com/u/9713279/20140422145308628.pdf
>
> My question is ? is my understanding of the view up right ?
>
>
> Med venlig hilsen/Best regards,
>
> Anne Iversen
>
> ____________________________________________
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>
> Anne Iversen
> PhD, MSc Energy, Sustainability Engineer
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