[Radiance-general] Ray-tracing with Radiance
Guglielmetti, Robert
Robert.Guglielmetti at nrel.gov
Mon Aug 10 10:03:49 PDT 2015
There is a daysim-specific mailing list that may be useful for some of
your questions:
http://www.radiance-online.org/community/mailing-lists/subscribe/radiance-d
aysim
I can tell you that if you're planning to use rcontrib and do 3- or
5-phase type stuff, you definitely should be using a recent version of
Radiance. Either build from latest source, or use one of the NREL
pre-built packages (I recommend v5):
https://github.com/NREL/Radiance/releases/tag/5.0.a.3
On 8/10/15, 9:14 AM, "Ikrima Amaireh" <ezxia at nottingham.ac.uk> wrote:
>Dear Germ?n,
>
>Many thanks for you. I agree with you totally that all Radiance works
>need to apply ray-tracing approach as the core principle of it. However,
>what I meant by using ray-tracing in radiance, was the using of RTRACE
>directly through stand-alone radiance tool (as you kindly mentioned).
>
>As you clarified, Daysim uses 2-phase method to do annual simulation (2nd
>phase) fast, based on pre-calculated Daylight Coefficient Matrix (1st
>phase). Now, if I need to produce the illuminance levels (produced by
>specific CFS) at the Workplane under static scene, can I still use Daysim
>for that? Or, shall I stick to RTRACE tool directly through pure Radiance?
>
>And, if I have to stick to using Pure Radiance (RTRACE), is the method
>detailed in the attached document (hope, you see that: where Geometry and
>Workplane sensors are built in Ecotect and directly exported to Radiance
>engine), is it still valid?
>
>
>Finally, in both cases (using pure Radiance and/or Daysim), shall we
>replace the Radiance tool (works as engine) by the latest released
>version (i.e. Version 4.2 or recent?) as the one works with
>Ecotect-Radiance approach (I'm not sure about Daysim, yet) is old version
>(2.0; in think!)?
>
>
>Really, I am grateful to you for your appreciated help and looking to
>hear from you again :)
>
>Regards,,,
>
>Ikrima
>
>
>
>
>
>> As some of you may remember, I am trying to model a set of CFS to
>>compare their effect on indoor horizontal illuminance of a room.
>So far, I have been advised by you for several stages, which really
>helped me a lot for better understanding of radiance and how it works.
>Now, I have a question about how I use ray-tracing method in radiance? Is
>it similar to the way explained through the following attachment?
>As here, calculations are run using Radiance engine but Ecotect or Daysim
>interface (for geometry modelling and material assignment).
>Document:
>http://web.mit.edu/sustainabledesignlab/projects/TeachingResources/Getting
>StartedwithEcotectRadianceDaysim.pdf
>
>I hope if you can kindly advise me on that asap, please?
>
>
>Ikrima,
>
>Strictly speaking, Radiance always use ray-tracing. Whenever you call
>RPICT, RTRACE or RCONTRIB, there will always be a ray-tracing simulation
>performed. However, when you want to perform annual simulations, you will
>want to do as few ray-tracing simulations as possible since they take
>time.
>RTRACE, for example, is a method used to calculate the illuminance or
>luminance of a point (sensor) in a static scene. Doing this for a whole
>year would require 8760 or more RTRACE calls, which means 8760 or more
>ray-tracing simulations, which is slow.
>
>Accordingly, Daysim (which uses the 2-phase method) runs one ray-tracing
>simulation that calculates the Daylight Coefficient matrix (this can be
>done in pure radiance by using RCONTRIB). This matrix relates the sensors
>(workplane?) in the scene with the sky, mich means that you can modify
>the sky and quickly evaluate illuminance in the same points. This allows
>performing annual simulations fast (only the sky changes in a static
>annual simulation). 3 and 5 phase method are extensions to this that
>allow also modifying the CFSs in the scene.
>
>Hope that clarify a little bit.
>
>
>
>
>-----Original Message-----
>From: radiance-general-request at radiance-online.org
>[mailto:radiance-general-request at radiance-online.org]
>Sent: 10 August 2015 14:20
>To: radiance-general at radiance-online.org
>Subject: Radiance-general Digest, Vol 138, Issue 12
>
>Send Radiance-general mailing list submissions to
> radiance-general at radiance-online.org
>
>To subscribe or unsubscribe via the World Wide Web, visit
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>or, via email, send a message with subject or body 'help' to
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>
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>
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>"Re: Contents of Radiance-general digest..."
>
>
>Today's Topics:
>
> 1. Re: Ray-tracing with Radiance (Germ?n Molina Larrain)
>
>
>----------------------------------------------------------------------
>
>Message: 1
>Date: Mon, 10 Aug 2015 10:19:18 -0300
>From: Germ?n Molina Larrain <germolinal at gmail.com>
>To: Radiance general discussion <radiance-general at radiance-online.org>
>Subject: Re: [Radiance-general] Ray-tracing with Radiance
>Message-ID:
>
><CAF-iH4LVHB_V+Vmy-mSiv2EtUE25KDxtTAyJfao5Mi6fzFDU1g at mail.gmail.com>
>Content-Type: text/plain; charset="utf-8"
>
>Ikrima,
>
>Strictly speaking, Radiance always use ray-tracing. Whenever you call
>RPICT, RTRACE or RCONTRIB, there will always be a ray-tracing simulation
>performed. However, when you want to perform annual simulations, you will
>want to do as few ray-tracing simulations as possible since they take
>time.
>RTRACE, for example, is a method used to calculate the illuminance or
>luminance of a point (sensor) in a static scene. Doing this for a whole
>year would require 8760 or more RTRACE calls, which means 8760 or more
>ray-tracing simulations, which is slow.
>
>Accordingly, Daysim (which uses the 2-phase method) runs one ray-tracing
>simulation that calculates the Daylight Coefficient matrix (this can be
>done in pure radiance by using RCONTRIB). This matrix relates the sensors
>(workplane?) in the scene with the sky, mich means that you can modify
>the sky and quickly evaluate illuminance in the same points. This allows
>performing annual simulations fast (only the sky changes in a static
>annual simulation). 3 and 5 phase method are extensions to this that
>allow also modifying the CFSs in the scene.
>
>Hope that clarify a little bit.
>
>Best,
>
>Germ?n
>
>
>
>2015-08-10 8:51 GMT-03:00 Ikrima Amaireh <ezxia at nottingham.ac.uk>:
>
>> Hello Robert,
>> Hello all,
>>
>> As some of you may remember, I am trying to model a set of CFS to
>> compare their effect on indoor horizontal illuminance of a room. So
>> far, I have been advised by you for several stages, which really
>> helped me a lot for better understanding of radiance and how it works.
>>
>> Now, I have a question about how I use ray-tracing method in radiance?
>> Is it similar to the way explained through the following attachment?
>> As here, calculations are run using Radiance engine but Ecotect or
>> Daysim interface (for geometry modelling and material assignment).
>>
>> Document:
>> http://web.mit.edu/sustainabledesignlab/projects/TeachingResources/Get
>> tingStartedwithEcotectRadianceDaysim.pdf
>>
>> I hope if you can kindly advise me on that asap, please?
>>
>>
>> Best regards
>> Ikrima
>>
>>
>>
>> -----Original Message-----
>> From: radiance-general-request at radiance-online.org [mailto:
>> radiance-general-request at radiance-online.org]
>> Sent: 12 July 2015 20:37
>> To: radiance-general at radiance-online.org
>> Subject: Radiance-general Digest, Vol 137, Issue 12
>>
>> Send Radiance-general mailing list submissions to
>> radiance-general at radiance-online.org
>>
>> To subscribe or unsubscribe via the World Wide Web, visit
>>
>> http://www.radiance-online.org/mailman/listinfo/radiance-general
>> or, via email, send a message with subject or body 'help' to
>> radiance-general-request at radiance-online.org
>>
>> You can reach the person managing the list at
>> radiance-general-owner at radiance-online.org
>>
>> When replying, please edit your Subject line so it is more specific
>> than
>> "Re: Contents of Radiance-general digest..."
>>
>>
>> Today's Topics:
>>
>> 1. Git for Windows and starting tutorials (Ikrima Amaireh)
>>
>>
>> ----------------------------------------------------------------------
>>
>> Message: 1
>> Date: Sun, 12 Jul 2015 20:36:19 +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] Git for Windows and starting tutorials
>> Message-ID:
>> <
>> D697763F9F216044A99BC674C00561961358CA9C4C at EXCHANGE1.ad.nottingham.ac.
>> uk>
>>
>> Content-Type: text/plain; charset="us-ascii"
>>
>> Hi Robert,
>>
>> Many thanks for your help.
>>
>> I have installed Git for Windows as you adviced :) Now, Before I start
>> with 3 or 5-phase tutorials, I'm thinking to go through "radiance
>>tutorial"
>> (by Axel Jacobs) as a beginner with almost a shallow
>> knowledge/experience of radiance. So, do recommend this (radiance
>> tutorial would be enough to start with 3 or 5-phase methods and
>> understanding of BSDF data approach,
>> etc) or advice another tutorial/source for better understanding of
>> radiance basics (using command prompt)?
>>
>> Many thanks again :)
>>
>> Regards
>> Ikrima
>>
>>
>>
>> ------------------------------
>>
>> Message: 2
>> Date: Fri, 10 Jul 2015 15:52:23 +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] Radiance-general Digest, Vol 137,
>> Issue 8
>> Message-ID: <D1C542EA.1AE88%Robert.Guglielmetti at nrel.gov>
>> Content-Type: text/plain; charset="us-ascii"
>>
>> OK so it sounds like you first tried the Windows installer (presumably
>> a NREL-provided one such as this:
>> https://github.com/NREL/Radiance/releases/download/5.0.a.3/radiance-5.
>> 0.a-w in64.exe), and this most likely worked fine, you just had some
>> issues actually *doing* anything with it. This is normal. =)
>>
>> I recommend you install Git for windows (https://msysgit.github.io/),
>> as that will add a little BASH emulator in your Windows system. This
>> way you can run most of the commands exactly as they appear in most of
>> the tutorials out there that are written from a UNIX perspective (as
>> you point out). If you run the "Git BASH shell" you will be able to
>> try out all the multi-phase methods, use and generate BSDFs, etc. Once
>> you have Git for Windows installed, head over to Andy McNeil's
>> tutorials for 3- and 5-phase, fire up the Git BASH shell (it'll be in
>> the Git program group in the Windows start menu), and get started!
>>
>> One thing to keep in mind is that when running any commands that
>> read/write data (e.g. rcontrib), be sure to use ASCII format rather
>> than float. Windows has issues with float data (among many other
>>things).
>>
>> Good luck!
>>
>> - Rob
>>
>> On 7/10/15, 8:08 AM, "Ikrima Amaireh" <ezxia at nottingham.ac.uk> wrote:
>>
>> >Hi Robert,
>> >
>> >My PC is running on Windows 7 Enterprise.
>> >Initially, I installed Radiance for Window using its installer but I
>> >found that most of the tutorials are provided for pc with Linux
>> >and/or Linux-like operating systems; So I had to install try learnix
>> >(that did not work) and Ubuntu (also did not work)!
>> >Finally, I tried to use Cygwin to run Radiance on Window OS. I could
>> >install Cygwin (works fine), Xming (not sure if working) and Radiance
>> >(not all its programs are working!).
>> >
>> >I'm a bit confused as I'm not sure if running Radiance on windows
>> >using Cygwin will be enough for carrying my work. For example, can I
>> >work out phases methods and generate BSDF data?
>> >
>> >I wish if you can help me to do that.
>> >
>> >Many thanks
>> >ikrima
>> >
>> >
>> >
>> >------------------------------
>> >
>> >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: 3
>> Date: Fri, 10 Jul 2015 17:34:30 +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] Modelling CFS
>> Message-ID:
>> <
>> D697763F9F216044A99BC674C00561961358CA9BAF at EXCHANGE1.ad.nottingham.ac.
>> uk>
>>
>> Content-Type: text/plain; charset="us-ascii"
>>
>> 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: radiance-general-request at radiance-online.org [mailto:
>> radiance-general-request at radiance-online.org]
>> Sent: 09 July 2015 19:56
>> To: radiance-general at radiance-online.org
>> Subject: Radiance-general Digest, Vol 137, Issue 8
>>
>> Send Radiance-general mailing list submissions to
>> radiance-general at radiance-online.org
>>
>> To subscribe or unsubscribe via the World Wide Web, visit
>>
>> http://www.radiance-online.org/mailman/listinfo/radiance-general
>> or, via email, send a message with subject or body 'help' to
>> radiance-general-request at radiance-online.org
>>
>> You can reach the person managing the list at
>> radiance-general-owner at radiance-online.org
>>
>> When replying, please edit your Subject line so it is more specific
>> than
>> "Re: Contents of Radiance-general digest..."
>>
>>
>> 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!"
>>
>>
>>
>>
>> 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: 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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