[Radiance-general] Modelling CFS
Germán Molina Larrain
germolinal at gmail.com
Fri Jul 10 09:43:34 PDT 2015
If it is just for a few "moments" of the day, I would just use ray-tracing.
Regarding "how do I draw...", I have to say that there are several options.
I am not sure how flexible is Ecotect to draw CFS... but there are two
exporters from SketchUp: SU2RAD and Groundhog. As the developer of the
latter, I would recommend you to ask someone else about it, because I think
it is awesome, haha.
Regards
2015-07-10 13:34 GMT-03:00 Ikrima Amaireh <ezxia at nottingham.ac.uk>:
> Hi all,
>
> Thanks Robert and Larrain for your detailed replies, that helped me a lot.
>
> I would summarise here what I got form your appreciated replies, as
> following:
> - Radiance is convenient and best of tools to model daylighting due to its
> ray-tracing method.
> - 3 or 5-phases methods are used to facilitate the calculations.
> - Generating BSDF data is also used to facilitate these calculations but
> it is limited to Klems resolution of some CFS.
>
> Initially, I'm not planning to do annual calculations. It's just for
> specific hours of the day and the target is to produce a illuminance levels
> for indoor grid under different CFSs. Hence, according to my understanding
> from Larrain words, I can use either 2-phase or Ray-tracing methods. My
> question is how can I draw/define the CFS geometry and Space for these
> calculations? Is it similar to the way use in Ecotect/Radiance calculations?
>
> Regards
> Ikrima
>
>
> -----Original Message-----
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> Sent: 09 July 2015 19:56
> To: radiance-general at radiance-online.org
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> Today's Topics:
>
> 1. CFS with Radiance (Ikrima Amaireh)
> 2. Could not install Radiance!!! (Ikrima Amaireh)
> 3. Re: Could not install Radiance!!! (Guglielmetti, Robert)
> 4. Re: CFS with Radiance (Guglielmetti, Robert)
> 5. Re: CFS with Radiance (Germ?n Molina Larrain)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Thu, 9 Jul 2015 17:26:29 +0100
> From: Ikrima Amaireh <ezxia at nottingham.ac.uk>
> To: "radiance-general at radiance-online.org"
> <radiance-general at radiance-online.org>
> Cc: Ikrima Amaireh <ezxia at nottingham.ac.uk>
> Subject: [Radiance-general] CFS with Radiance
> Message-ID:
> <
> D697763F9F216044A99BC674C00561961358CA9710 at EXCHANGE1.ad.nottingham.ac.uk>
>
> Content-Type: text/plain; charset="us-ascii"
>
> Hi G. Larrain,
>
> Thanks for your detailed clarification (below).
>
> I wonder if you kindly can help me toward better understanding and
> answering the following:
>
> We agreed that for daylight modelling of spaces with CFS, Radiance is a
> suitable tool as it applies ray-tracing method. And for annual and/or
> climate-based daylight calculations, as calculation time becomes a critical
> factor, using BSDF data for CFS is highly recommended to tackle the task
> with radiance (using phases methods). However:
>
> - if someone needs to perform daylight calculations for given space with
> different CFS (different cases for comparison purposes) to get illumination
> levels for horizontal grid points (and not pictures nor scenes), is
> Radiance still the most convenient option?
> - is it still needed to use any of the phase methods (2, 3 or 5)?
> - most importantly, is it still needed to get BSDF data for CFS or just
> can model the detailed CFS in Radiance (and, if yes, how?)
>
>
> Many thanks for your kind help :)
>
> Regards
> Ikrima
>
>
> "Ikrima,
>
> I am going to try to build the puzzle of CFS, Phases, BSDF and
> calculations.... at least the way I understand it.
>
> *CFS* are those systems that, via interreflection or other light transport
> phenomena, redirect light (or solar radiation). Thus, in order to get a
> reliable result you will have to consider all the phenomena involved.
> Then, *common
> simple performance indexes*, such as the miss-used Shading Coefficient and
> the Aperture Percentage, *always loose a lot of information, trying to
> reduce all the complex behavior of a CFS to one single number*. We all know
> that venetian blinds are more "transparent" from certain viewing directions
> than from others, but these performance indexes do not tell you that.
>
> Now... Radiance can certainly perform calculations of spaces with CFS
> using its "common" Ray-tracing. However, this may be slow for some purposes
> (i.e.
> annual simulations and climate-based daylight modelling), and *this is why
> 2, 3 and 5 phase methods have been developed*. The *BSDF* representation, I
> would say, goes in the same direction... It allow summarizing all the
> bounces, reflections, refractions, etc. that occure withing the CFS in a
> single matrix or tensor.* By using BSDFs*, Radiance itself and other tools
> (i.e. EnergyPlus) can treat CFS as blackboxes, avoiding all the opcits
> within the system. A BSDF that uses the Klems Full representation has
> 21,045 numbers (instead of one, such as the Shading Coefficient).
>
> Being said all that, I would not trust a calculation method unless it can
> actually deal with the optics of a CFS that is drawn and/or it can use BSDF
> (or similar) information.
>
> Lets remember that a perforated screen, a venetian blind, a light
> diffusing device can all have a Shading Coefficient of 50%, but all of them
> will behave very differently. I made some presentations about this on my
> previous work (we sold complex Shading Devices), trying to promote the use
> of BSDF in EnergyPlus calculations... the differences (in solar heat gains)
> were more than considerable.
>
> I hope that someone else gives us his/her perspective on this topic...
> there are a lot of concepts that I might be misunderstanding.
>
> Best!"
>
>
>
>
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> ------------------------------
>
> Message: 2
> Date: Thu, 9 Jul 2015 17:38:41 +0100
> From: Ikrima Amaireh <ezxia at nottingham.ac.uk>
> To: "radiance-general at radiance-online.org"
> <radiance-general at radiance-online.org>
> Cc: Ikrima Amaireh <ezxia at nottingham.ac.uk>
> Subject: [Radiance-general] Could not install Radiance!!!
> Message-ID:
> <
> D697763F9F216044A99BC674C00561961358CA9719 at EXCHANGE1.ad.nottingham.ac.uk>
>
> Content-Type: text/plain; charset="us-ascii"
>
> Hi all,
>
> After one a few weeks of trying, I could not manage to install radiance
> properly. I am almost disappointed! Please any help?
>
> Regards
> Ikrima
>
>
>
>
> This message and any attachment are intended solely for the addressee and
> may contain confidential information. If you have received this message in
> error, please send it back to me, and immediately delete it.
>
> Please do not use, copy or disclose the information contained in this
> message or in any attachment. Any views or opinions expressed by the
> author of this email do not necessarily reflect the views of the University
> of Nottingham.
>
> This message has been checked for viruses but the contents of an
> attachment may still contain software viruses which could damage your
> computer system, you are advised to perform your own checks. Email
> communications with the University of Nottingham may be monitored as
> permitted by UK legislation.
>
>
>
>
> ------------------------------
>
> Message: 3
> Date: Thu, 9 Jul 2015 16:44:49 +0000
> From: "Guglielmetti, Robert" <Robert.Guglielmetti at nrel.gov>
> To: "radiance-general at radiance-online.org"
> <radiance-general at radiance-online.org>
> Subject: Re: [Radiance-general] Could not install Radiance!!!
> Message-ID: <D1C400AC.1ADAC%Robert.Guglielmetti at nrel.gov>
> Content-Type: text/plain; charset="us-ascii"
>
> Hi Ikrima,
>
> We'll need a bit more info, here. What OS are you on? How are you
> attempting to install it (using an installer, compiling from source, or
> what)? What happens when you try??
>
> On 7/9/15, 10:38 AM, "Ikrima Amaireh" <ezxia at nottingham.ac.uk> wrote:
>
> >Hi all,
> >
> >After one a few weeks of trying, I could not manage to install radiance
> >properly. I am almost disappointed! Please any help?
> >
> >Regards
> >Ikrima
> >
> >
> >
> >
> >This message and any attachment are intended solely for the addressee
> >and may contain confidential information. If you have received this
> >message in error, please send it back to me, and immediately delete it.
> >
> >Please do not use, copy or disclose the information contained in this
> >message or in any attachment. Any views or opinions expressed by the
> >author of this email do not necessarily reflect the views of the
> >University of Nottingham.
> >
> >This message has been checked for viruses but the contents of an
> >attachment may still contain software viruses which could damage your
> >computer system, you are advised to perform your own checks. Email
> >communications with the University of Nottingham may be monitored as
> >permitted by UK legislation.
> >
> >
> >_______________________________________________
> >Radiance-general mailing list
> >Radiance-general at radiance-online.org
> >http://www.radiance-online.org/mailman/listinfo/radiance-general
>
>
>
>
> ------------------------------
>
> Message: 4
> Date: Thu, 9 Jul 2015 17:29:39 +0000
> From: "Guglielmetti, Robert" <Robert.Guglielmetti at nrel.gov>
> To: "radiance-general at radiance-online.org"
> <radiance-general at radiance-online.org>
> Subject: Re: [Radiance-general] CFS with Radiance
> Message-ID: <D1C40477.1ADCA%Robert.Guglielmetti at nrel.gov>
> Content-Type: text/plain; charset="us-ascii"
>
> Some very quick replies and clarifications within:
>
> On 7/9/15, 10:26 AM, "Ikrima Amaireh" <ezxia at nottingham.ac.uk> wrote:
>
> >Hi G. Larrain,
> >
> >Thanks for your detailed clarification (below).
> >
> >I wonder if you kindly can help me toward better understanding and
> >answering the following:
> >
> >We agreed that for daylight modelling of spaces with CFS, Radiance is a
> >suitable tool as it applies ray-tracing method. And for annual and/or
> >climate-based daylight calculations, as calculation time becomes a
> >critical factor, using BSDF data for CFS is highly recommended to
> >tackle the task with radiance (using phases methods). However:
>
>
> BSDF data in an annual simulation context is generally limited to Klems
> basis BSDF data, which may not be high enough resolution for some CFS. And
> the 5-phase method, which can circumvent this, is not necessarily "quick".
> This is all still very much a quandary and the newest daylight metrics
> have added confusion to all of this, IMO.
>
>
> >
> >- if someone needs to perform daylight calculations for given space
> >with different CFS (different cases for comparison purposes) to get
> >illumination levels for horizontal grid points (and not pictures nor
> >scenes), is Radiance still the most convenient option?
>
>
> Absolutely. The lack of an image-as-output requirement does not change the
> fact that ray tracing is a good/convenient algorithm option for daylight
> simulation problems, especially when dealing with diffusing media and CFS
> in general. BSDFs allow you to do lots of "what-ifs", relatively quickly,
> but are beholden to the limitations of the resolution of the BSDF.
>
>
> >- is it still needed to use any of the phase methods (2, 3 or 5)?
>
>
> Is what still needed? BSDF data? Ray tracing? I don't know of other
> lighting simulation tools that can employ the multiphase methods. I would
> say BSDF data is optional for 2-phase, required for 3-phase, and optional
> for 5-phase.
>
> >- most importantly, is it still needed to get BSDF data for CFS or just
> >can model the detailed CFS in Radiance (and, if yes, how?)
>
>
> Again I'm confused as to what "it" is. A couple of approaches are
> available to you in general. If you have a geometric model of the CFS you
> can use Radiance (genBSDF) to make a BSDF of the CFS and use that in a 3-
> or 5-phase context. However in an annual/climate-based simulation context,
> you will be stuck with a Klems basis BSDF and that will not be very good
> resolution for a lot of CFS; here you may want to use the 5-phase method
> and stick the actual CFS geometry in the building model.
>
> Some things to consider here are the photon map, now a part of Radiance
> proper, or using the 2-phase method where appropriate. By 2-phase method I
> mean generating a daylight matrix for your calculation points (or view),
> and modeling the window material as-is. If the "CFS" is a shade cloth, you
> can approximate that with a Radiance "trans". Same for translucent panels.
> With this single daylight matrix, you can throw a vector of sky matrices
> at it and get an annual climate-based result very quickly. Problem is, we
> want to do stuff to the windows, sometimes at the time step level, so:
>
> Blinds and compact daylight redirection devices (e.g. Lightlouver) are
> best represented as BSDF, and if most of the redirected flux is headed up
> and away from the points of interest, a Klems basis BSDF is good enough
> IMO. In these cases you could use the 3-phase method. Problem is when you
> have a BSDF for blinds, and you also want to simulate the blinds-up
> condition (i.e. clear, specularly transmitting glass). Using a Klems basis
> BSDF for this is sub-optimal. You end up needing to do two annual
> simulations, one as 2-phase for the clear glass scenario, and again as a
> 3-phase (with a blinds BSDF for the transmission matrix) for the blinds
> down condition. If you have a lot of different window groups, your
> simulation space can get large in a hurry. But it's still do-able and you
> can get results that tell a story you simply couldn't tell 5 years ago,
> informing the newest daylight metrics as well.
>
>
>
>
>
>
> ------------------------------
>
> Message: 5
> Date: Thu, 9 Jul 2015 15:56:11 -0300
> From: Germ?n Molina Larrain <germolinal at gmail.com>
> To: Radiance general discussion <radiance-general at radiance-online.org>
> Subject: Re: [Radiance-general] CFS with Radiance
> Message-ID:
> <CAF-iH4LSr=y12F1khTrHh6hnf-kS=EmaFuo8uWKvHqMs=
> FZL-Q at mail.gmail.com>
> Content-Type: text/plain; charset="utf-8"
>
> I must say that I agree with Rob, however, a short answer that might help.
>
> For evaluating illuminance levels in a space with different CFS you,
> strictly speaking, DO NOT HAVE TO do anything. You may choose between
> different methods that have some pros and cons.
>
>
> *ray-tracing*
>
> - Requires ray-tracing for each time-step and each system, which is slow
> (*four systems simulated annualy in an hourly basis --> 4*8760 = 35,040
> simulations*.)
> - As accurate as it gets, if options are defined correctly.
>
>
> *2 phase method*
>
> - Do not need the BSDF
> - Requires ray-tracing for each CFS (*4 systems --> 4 ray-tracing
> simulations*)
> - After ray-tracing, annual simulation is fast.
>
> *3-phase method:*
>
> - Requires BSDF data in KLEMS basis, which may be slow to compute,
> unless it can be exported from WINDOW, for example, or such data has
> already been calculated (the idea is to make a database, I think).
> - Does not really work well for specular systems (Klems patches are too
> big)
> - Requires 2 ray-tracing runs, always (*4 systems --> 2 ray-tracing
> simulations*)
> - After ray-tracing and BSDF calculation, annual simulation is fast
>
> *5-phase method:*
>
> - Requires BSDF data in KLEMS basis AND/OR Tensor tree format, which
> may be slow to compute, unless it can be exported from WINDOW, for
> example,
> or such data has already been calculated (the idea is to make a
> database, I
> think).
> - Works well for specular systems
> - Requires 4 ray-tracing runs + 1 for each system, always (*4 systems
> --> 4+1 = 5 ray-tracing simulations*)
> - Hard to code...?
> - After ray-tracing and BSDF calculation, annual simulation is fast
>
>
> I would not say there is a recipe. If you have to choose between 1 or 2
> CFSs, maybe it is faster to just draw them and use the 2 phase method (or
> ray-tracing if an annual simulaton is not required). On the contrary, if
> you are going to test 10 different CFSs, 3 and 5 phases may make sense,
> since you reduce the expensive ray-tracing calculations... However, this
> will also depend on weather you have the BSDF data AND/OR if it makes sense
> to calculate it and store it AND/OR if you intend to simulate a dynamically
> controlled CFS.
>
> Best!
>
> 2015-07-09 14:29 GMT-03:00 Guglielmetti, Robert <
> Robert.Guglielmetti at nrel.gov>:
>
> > Some very quick replies and clarifications within:
> >
> > On 7/9/15, 10:26 AM, "Ikrima Amaireh" <ezxia at nottingham.ac.uk> wrote:
> >
> > >Hi G. Larrain,
> > >
> > >Thanks for your detailed clarification (below).
> > >
> > >I wonder if you kindly can help me toward better understanding and
> > >answering the following:
> > >
> > >We agreed that for daylight modelling of spaces with CFS, Radiance is
> > >a suitable tool as it applies ray-tracing method. And for annual
> > >and/or climate-based daylight calculations, as calculation time
> > >becomes a critical factor, using BSDF data for CFS is highly
> > >recommended to tackle the task with radiance (using phases methods).
> However:
> >
> >
> > BSDF data in an annual simulation context is generally limited to
> > Klems basis BSDF data, which may not be high enough resolution for
> > some CFS. And the 5-phase method, which can circumvent this, is not
> necessarily "quick".
> > This is all still very much a quandary and the newest daylight metrics
> > have added confusion to all of this, IMO.
> >
> >
> > >
> > >- if someone needs to perform daylight calculations for given space
> > >with different CFS (different cases for comparison purposes) to get
> > >illumination levels for horizontal grid points (and not pictures nor
> > >scenes), is Radiance still the most convenient option?
> >
> >
> > Absolutely. The lack of an image-as-output requirement does not change
> > the fact that ray tracing is a good/convenient algorithm option for
> > daylight simulation problems, especially when dealing with diffusing
> > media and CFS in general. BSDFs allow you to do lots of "what-ifs",
> > relatively quickly, but are beholden to the limitations of the
> resolution of the BSDF.
> >
> >
> > >- is it still needed to use any of the phase methods (2, 3 or 5)?
> >
> >
> > Is what still needed? BSDF data? Ray tracing? I don't know of other
> > lighting simulation tools that can employ the multiphase methods. I
> > would say BSDF data is optional for 2-phase, required for 3-phase, and
> > optional for 5-phase.
> >
> > >- most importantly, is it still needed to get BSDF data for CFS or
> > >just can model the detailed CFS in Radiance (and, if yes, how?)
> >
> >
> > Again I'm confused as to what "it" is. A couple of approaches are
> > available to you in general. If you have a geometric model of the CFS
> > you can use Radiance (genBSDF) to make a BSDF of the CFS and use that
> > in a 3- or 5-phase context. However in an annual/climate-based
> > simulation context, you will be stuck with a Klems basis BSDF and that
> > will not be very good resolution for a lot of CFS; here you may want
> > to use the 5-phase method and stick the actual CFS geometry in the
> building model.
> >
> > Some things to consider here are the photon map, now a part of
> > Radiance proper, or using the 2-phase method where appropriate. By
> > 2-phase method I mean generating a daylight matrix for your
> > calculation points (or view), and modeling the window material as-is.
> > If the "CFS" is a shade cloth, you can approximate that with a Radiance
> "trans". Same for translucent panels.
> > With this single daylight matrix, you can throw a vector of sky
> > matrices at it and get an annual climate-based result very quickly.
> > Problem is, we want to do stuff to the windows, sometimes at the time
> step level, so:
> >
> > Blinds and compact daylight redirection devices (e.g. Lightlouver) are
> > best represented as BSDF, and if most of the redirected flux is headed
> > up and away from the points of interest, a Klems basis BSDF is good
> > enough IMO. In these cases you could use the 3-phase method. Problem
> > is when you have a BSDF for blinds, and you also want to simulate the
> > blinds-up condition (i.e. clear, specularly transmitting glass). Using
> > a Klems basis BSDF for this is sub-optimal. You end up needing to do
> > two annual simulations, one as 2-phase for the clear glass scenario,
> > and again as a 3-phase (with a blinds BSDF for the transmission
> > matrix) for the blinds down condition. If you have a lot of different
> > window groups, your simulation space can get large in a hurry. But
> > it's still do-able and you can get results that tell a story you
> > simply couldn't tell 5 years ago, informing the newest daylight metrics
> as well.
> >
> >
> >
> >
> > _______________________________________________
> > Radiance-general mailing list
> > Radiance-general at radiance-online.org
> > http://www.radiance-online.org/mailman/listinfo/radiance-general
> >
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>
> This message and any attachment are intended solely for the addressee
> and may contain confidential information. If you have received this
> message in error, please send it back to me, and immediately delete it.
>
> Please do not use, copy or disclose the information contained in this
> message or in any attachment. Any views or opinions expressed by the
> author of this email do not necessarily reflect the views of the
> University of Nottingham.
>
> This message has been checked for viruses but the contents of an
> attachment may still contain software viruses which could damage your
> computer system, you are advised to perform your own checks. Email
> communications with the University of Nottingham may be monitored as
> permitted by UK legislation.
>
>
> _______________________________________________
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