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-----
From: [email protected] [mailto:[email protected]]
Sent: 09 July 2015 19:56
To: [email protected]
Subject: Radiance-general Digest, Vol 137, Issue 8
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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 <[email protected]>
To: "[email protected]"
<[email protected]>
Cc: Ikrima Amaireh <[email protected]>
Subject: [Radiance-general] CFS with Radiance
Message-ID:
<D697763F9F216044A99BC674C00561961358CA9710@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 <[email protected]>
To: "[email protected]"
<[email protected]>
Cc: Ikrima Amaireh <[email protected]>
Subject: [Radiance-general] Could not install Radiance!!!
Message-ID:
<D697763F9F216044A99BC674C00561961358CA9719@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
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------------------------------
Message: 3
Date: Thu, 9 Jul 2015 16:44:49 +0000
From: "Guglielmetti, Robert" <[email protected]>
To: "[email protected]"
<[email protected]>
Subject: Re: [Radiance-general] Could not install Radiance!!!
Message-ID: <D1C400AC.1ADAC%[email protected]>
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" <[email protected]> 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
IkrimaThis 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
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------------------------------
Message: 4
Date: Thu, 9 Jul 2015 17:29:39 +0000
From: "Guglielmetti, Robert" <[email protected]>
To: "[email protected]"
<[email protected]>
Subject: Re: [Radiance-general] CFS with Radiance
Message-ID: <D1C40477.1ADCA%[email protected]>
Content-Type: text/plain; charset="us-ascii"
Some very quick replies and clarifications within:
On 7/9/15, 10:26 AM, "Ikrima Amaireh" <[email protected]> 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 <[email protected]>
To: Radiance general discussion <[email protected]>
Subject: Re: [Radiance-general] CFS with Radiance
Message-ID:
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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 < [email protected]>:
Some very quick replies and clarifications within:
On 7/9/15, 10:26 AM, "Ikrima Amaireh" <[email protected]> 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
[email protected]
http://www.radiance-online.org/mailman/listinfo/radiance-general
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University of Nottingham.
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