[Radiance-general] Radiance 5.0 installation on ubuntu 14.04

[Greg Ward]

Hi Humberto,

It does help to know a little context about your model.  Yes, using "u=Z" for vertical windows in any orientation and "u=Y" for the sky or skylights is the standard approach.  This is in fact the default behavior in rfluxmtx if no up-direction is specified, but it's best to be explicit about it.  The "u=Y" for horizontal relates to the standard choice of Y for "north" in gensky and gendaylit.  You can of course rotate the sky during your dctimestep phase, and this is much faster than rotating your surface orientations and re-running rfluxmtx.

In other words, I recommend running rfluxmtx once for the interior illuminances and their relation to your inward-facing window.  Then, you will run it again to connect the still inward-facing window polygon as a source this time and its flux relationship to the ground and sky hemisphere.  This brings up another important point, which is how best to specify the ground+sky in rfluxmtx.  I discussed this durning my 2014 Workshop presentation on new Radiance features:

	Radiance Code Update 2014  http://www.radiance-online.org/community/workshops/2014-london/presentations/day1/Ward_WhatIsNew.pdf

The discussion of rfluxmtx starts at slide 38.  Pay special attention to the example on slide 42, where I show how to combine a uniform ground hemisphere with a Reinhart sky description.

Once you have your two flux matrices, you will pipe the output of gensky or (more likely) gendaylit to xform -rz to rotate in the opposite direction of your model's rotation, then through genskyvec into dctimestep, where you will combine the matrices with the desired window glazing+shading BTDF to compute the irradiance values for your interior points.  Alternatively, you may run gendaymtx for a whole year, using its built-in -rz option rather than xform.

Cheers,
-Greg

> From: Humberto Antunes <hs.antunes at campus.fct.unl.pt>
> Subject: Re: [Radiance-general] Radiance 5.0 installation on ubuntu 14.04
> Date: March 19, 2016 5:30:51 AM PDT
> 
> Thanks Greg, that definitely helped.
> 
> So we really need to be careful about the surface normal, if the objective is to get illuminance values on the work plane inside a room the normal of the window should face the interior, is that it?
> 
> There is just something i cant't understand, defining the up-direction, in the windows located in vertical surfaces the up-direction is allways "u=Z" no matter the orientation of the window, while in the ground or sky surface in the daylight matrix receiver file up-direction is "u=Y", right?
> 
> It may be import to say that my model is a simple office room with only a window, a lot like Axel's model on the rcontrib lesson, and i will have to analyse the illuminance at the work plane for the four different orientations of the window with different control parameters for the shading device applied to that same window.
> 
> Best regards
> Humberto A.
> 
> 
> 2016-03-18 23:50 GMT+00:00 Greg Ward <gregoryjward at gmail.com>:
> Oh, but I did neglect to mention a critical point, which is that rfluxmtx figures out the hemisphere orientation(s) from the surface or surfaces you specify in your source and receiver files.  So, it's very important that surface normals are directed in a certain way -- specifically, receiver normals point in the direction of the sampled hemisphere, and source normals point *away* from the hemisphere we want to sample.
> 
> Though this may seem counter-intuitive, it follows naturally from the typical orientation of windows in Radiance, whose normals face the interior.  When the windows are acting as the receivers in a matrix calculation, such as for a view or illuminance value matrix, their normal is looking towards the interior hemisphere being sampled.  When their role changes to make them the source surfaces, as when you calculate the exterior daylight matrix, they are still facing the correct direction to have their opposite-side hemisphere send out samples to the exterior.
> 
> In this way, rfluxmtx allows you to re-use your receiver description in one run as the source description in another run.
> 
> I'm hoping this makes sense, because I mention it in the man page, but it's not quite obvious and I did it the wrong way around the last time I used the tools, myself(!)
> 
> Best,
> -Greg
> 
> rfluxmtx.pdf
> 
>> From: "Gregory J. Ward" <gregoryjward at gmail.com>
>> Subject: Re: [Radiance-general] Radiance 5.0 installation on ubuntu 14.04
>> Date: March 18, 2016 4:40:09 PM PDT
>> 
>> Hi Humberto,
>> 
>> The rfluxmtx command takes over for genklemsamp and calls rcontrib with the options needed for correct operation.  You don't need to specify the bin or the .cal file(s), as rfluxmtx takes care of that part.  You do need to set both the "u=Z" (or whatever) up-direction and the desired hemispherical sampling type (e.g., "h=r4") in your Radiance scene description handed to rfluxmtx as the source or receiver(s).
>> 
>> The reinhartb.cal file is more general than the original reinhart.cal file, and uses slightly different mechanisms (hence the need for a new name).
>> 
>> I hope this helps, and thanks to everyone for pitching in.  I realize that the changes made post-tutorial have caused a good deal of confusion, but we hope to get it all sorted out in the end.
>> 
>> Cheers,
>> -Greg
>> 
>>> From: Humberto Antunes <hs.antunes at campus.fct.unl.pt>
>>> Subject: Re: [Radiance-general] Radiance 5.0 installation on ubuntu 14.04
>>> Date: March 18, 2016 2:49:55 PM PDT
>>> 
>>> Hello again everybody,
>>> 
>>> I have a question related to the command rfluxmtx.
>>> While using rcontrib to generate the view matrix we had to set the window orientation with the command -b kbinS or (N,E or W), how do we do that in the rfluxmtx? Is it set by the "u" variable or it is not needed to do this with the rfluxmtx command?
>>> 
>>> Also, as reinhart.cal file been replaced for the reinhartb.cal?
>>> 
>>> Best regards
>>> Humberto A.
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