[Radiance-general] RE: Radiance and EcoTect
Reinhart, Christoph
Christoph.Reinhart at nrc-cnrc.gc.ca
Mon May 15 15:57:52 CEST 2006
Hi Nick,
I assume that John is referring to a small c-program that comes with Daysim called gen_single_office.exe. It is a very basic but useful program that allows you to write out RADIANCE scene files and sensor grids for single and open plan offices. I find the script useful for parametric studies as all geometry and material properties are set via the command line. In case I want to get a transmissivity value, I would type something like
gen_single_office -o scene.rad -I sensor.pts -t 80
In the resulting scene.rad file you get the transmissivity value in the material description for glazing: 0.871538.
I am using the simplified glass model in Radiance because I currently do not trust the Optics/Windows output to Radiance (mainly because (a) I still do not properly understand it and (b) because I am not aware of a proper validation study). Maybe somebody from LBNL could enlighten us? If Windows/Optics output into Radiance was indeed reliable, it would be invaluable for the Radiance community.
Christoph
-----Original Message-----
From: radiance-general-bounces at radiance-online.org [mailto:radiance-general-bounces at radiance-online.org] On Behalf Of John An
Sent: Saturday, May 13, 2006 11:38 PM
To: radiance-general at radiance-online.org
Subject: [Radiance-general] RE: Radiance and EcoTect
Nick,
Christoph Reinhart has a little script that allows you to input your desired transmissivity, and you can extract the correct Radiance definition from the output. I think that may be the way to go for your purposes. I would contact Christoph to see if you can get your hands on the script. Your other option is to select a few actual glasses with the transmissivity that you desire, and test to make sure that they all produce similar results.
John
Nick Doylend wrote:
Thanks very much for your suggestions.
I looked briefly at outputting glazing data from Optics. It's probably the way to go if I want to model a 'real' glazing type. I don't really understand how the BRTDfunc is used; it sets the surface reflectance as well as transmittance doesn't it? At the moment I'm only considering a 'notional' glazing so I'm just calculating the transmissivity and editing the Radiance file output from Ecotect by hand. For typical glass types, how much difference would using the BRTDfunc definitions make to my internal daylight calculations?
As far as reliability of results is concerned, It seems Radiance (in the hands of an expert user) is more capable of realistic results than Ecotect.
I've noticed that Ecotect's speed of calculation is influenced quite significantly by the number of windows. It doesn't appear to make much difference to Radiance's calculation time. I guess it's down to the differences in calculation method but it does make me wonder how well Ecotect handles models with many windows.
On the other hand, I find Radiance doesn't seem to behave quite as expected.
For example, for an equal glazed area I would expect fewer, larger rooflights to give the same average %DF across the whole floor as more, smaller rooflights. In this case, Ecotect seems to behave as I expect, but Radiance suggests fewer, larger rooflights give the better average %DF. I wonder why this should be. Maybe my assumption is incorrect.
Nick
---------
John An
Environmental Designer
Atelier Ten
-----Original Message-----
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Sent: Friday, May 12, 2006 6:01 AM
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Subject: Radiance-general Digest, Vol 27, Issue 9
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Today's Topics:
1. Re: water simulation (Ignacio Mun?rriz)
2. Re: Glass & MTL file troubles... (or how to go from Revit to
Radiance with little pain...) (Jeffrey McGrew)
3. Re: Glass & MTL file troubles... (or how to go from Revit to
Radiance with little pain...) (Jeffrey McGrew)
4. Re: Glass & MTL file troubles... (or how to go from Revit to
Radiance with little pain...) (Jeffrey McGrew)
5. Re: Glass & MTL file troubles... (or how to go from Revit to
Radiance with little pain...) (Lars Grobe)
6. Re: water simulation (Gregory J. Ward)
----------------------------------------------------------------------
Message: 1
Date: Thu, 11 May 2006 14:13:43 +0200
From: Ignacio Mun?rriz <info at aisarquitectura.com>
Subject: Re: [Radiance-general] water simulation
To: "Radiance general discussion"
<radiance-general at radiance-online.org>
Message-ID: <000901c674f4$5ca3aab0$0301a8c0 at aisxeon>
Content-Type: text/plain; charset="iso-8859-1"
Thanks Greg, i think i'm near to get it, but there is something that is not working, i dont know if Rdot is the DOT product or the -DOT product, i tried the two but it is still not working, i´ve been trying to do some tests with calc and it seems to work but something must be wrong because rpict gives the aiming error, what is the best tool in radiance to test this kind of things, i say, testing cal files while sending rays
void prism2 water
9 transm dx dy dz reflect dxx dyy dzz water.cal
0
3 1 1 1
####water.cal#####
nrwater=1.3;
cos1=if(Rdot,Rdot,-Rdot);
nratio=if(Rdot,1/nrwater,nrwater);
dnormx=if(Rdot,Nx,-Nx);
dnormy=if(Rdot,Ny,-Ny);
dnormz=if(Rdot,Nz,-Nz);
d3=1.0-(nratio*nratio*(1.0 -(cos1*cos1))); cos2=sqrt(d3); d1bis=cos1; d2bis=nratio*cos2; d1t=(d1bis-d2bis)/(d1bis+d2bis); reflpp=d1t*d1t; d1p=1.0/cos1; d2=nratio/cos2; d1=(d1p-d2)/(d1p+d2); reflp=reflpp+(d1*d1); refl=reflp*.5; transp=1.0 -refl; trans=transp*nratio*nratio;
reflect=if(d3,refl,1.0);
transm=if(d3,trans,0.0);
dm=nratio*cos1 - cos2;
dx=nratio*Dx+dm*dnormx;
dy=nratio*Dy+dm*dnormy;
dz=nratio*Dz+dm*dnormz;
dxx=Dx+2.0*cos1*dnormx;
dyy=Dy+2.0*cos1*dnormy;
dzz=Dz+2.0*cos1*dnormz;
----- Original Message -----
From: "Gregory J. Ward" <gregoryjward at gmail.com>
To: "Radiance general discussion" <radiance-general at radiance-online.org>
Sent: Wednesday, May 10, 2006 10:02 PM
Subject: Re: [Radiance-general] water simulation
Hi Ignacio,
Your problem stems from the fact that your modified angles do not obey reciprocity, which says that if you reverse the ray (light) direction, then the angles remain the same on either side. Both prisma and prism2 require this property to function. Implementing Snell's law correctly, you should get a working material.
The vector version of Snell's law may be found in ray/src/ dielectric.c, or in an easier-to-read form on Wikipedia:
http://en.wikipedia.org/wiki/Snell's_law
Note that the roles of the inside and outside indices of refraction,
n1 and n2, reverse when you come from one side of the water verses the other. The n of water is about 1.3, and air is of course 1.0.
(OK, quibblers, air is really 1.0003)
-Greg
> From: Ignacio Munárriz <info at aisarquitectura.com>
> Date: May 10, 2006 5:04:50 AM PDT
>
> I'm trying tom model water with the prism1 & prism2 primitives.
> I`ve been
> able to propagate the rays from sources using
>
> ...
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Message: 2
Date: Thu, 11 May 2006 08:33:13 -0700
From: Jeffrey McGrew <toast at becausewecan.org>
Subject: Re: [Radiance-general] Glass & MTL file troubles... (or how
to go from Revit to Radiance with little pain...)
To: Radiance general discussion <radiance-general at radiance-online.org>
Message-ID: <44635939.3010408 at becausewecan.org>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Rob Guglielmetti wrote:
> Ugh. Yeah, programs like Revit and 3DS, et al. make glazing planes as
> 3D objects with six polygons. No good. Your errors and problems are
> definitely related to this. mkillum expects a single polygon, looking
> in.
OK, that's what I thought. I'm not using Mkillum yet, just trying to make the windows into a Illum source with Skyfunc and not having much luck.
> Not sure how you're flattening the planes, but I'll bet you're still
> ending up with a pair of triangular polys representing the glass
> plane, and who the hell knows which way they're facing. mkillum likes
> regular polygons. Page 577 of Rendering with Radiance has the gory
> details. Not sure the answer to your problem, just stating the issues.
I'll look that up. Thanks for the confirmation.
I'm able to flatten the planes in Max via the 'Edit Poly' modifier.
Thankfully, all of those 6-sided polys have their Y-axis pointing the same way it appears, even if tilted/turned, so I can flatten them all with a single tool. However, this doesn't remove the side polys, and leaves you with two flat faces I suspect, so I'll have to research this method more.
> If you can grep the stuff out, I'd bet you could write something to
> take the result(s) and generate a corresponding .mat file, with shell
> scripting techniques, or python or perl, or whatever.
Yeah, my unix god friend pointed me towards AWK as a simple solution.
I'm just lazy, and can't write code quickly (not a programmer) so I was hoping that there might be a solution out there already.
> Sounds like a plan. The thing is, you are closer to real numbers than
> most lighting designers, by having the wherewithal to tackle Radiance.
> Don't short-change yourself. A good model and sound parameters in
> Radiance beats any of the tools commonly used in lighting design, IMO.
Didn't know that. Huh. Well, Revit produces very good models (other than this glass thing) so I'm halfway there I guess.
Jeffrey
------------------------------
Message: 3
Date: Thu, 11 May 2006 08:37:51 -0700
From: Jeffrey McGrew <toast at becausewecan.org>
Subject: Re: [Radiance-general] Glass & MTL file troubles... (or how
to go from Revit to Radiance with little pain...)
To: Radiance general discussion <radiance-general at radiance-online.org>
Message-ID: <44635A4F.2040901 at becausewecan.org>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Bleicher, Thomas wrote:
> I think your looking for high quality renderings of the interior, so
> you definitely want to use mkillum to restrict your scene to the interior.
> If it's just a crude rendering I'd create a sky and wouldn't bother
> much about the windows as light source.
>
That's what we've got going, it's a building with lots of glass and skylights and such. So do you think just having the windows be glass would be enough to get somewhat-close numbers? I fear that not making the glass a secondary light source, and just having it be, well, glass and only having the ray of sunlight bouncing around is going to give me bad numbers.
> You could write a script to delete polygons with material glass based
> on their area (reduce 6 sides to 2) and vicinity to already checked
> polygons (reduce 2 to one) but that's not going to be easy. You might
> be able to edit the windows in MAX to get a Radiance friendly geometry.
>
That's what I'm doing, I can edit them in Max via the 'Edit Poly'
modifier, but I'll need to research this more. I want to stay away from hand-editing much of anything, for I want to be able to go back and edit the Revit model, re-export to Max, and from there re-export to OBJ2RAD for quick revisions. So far, so good on that front, but this glass thing is leaving me stumped.
> Please see the man page for obj2rad. The top section describes
> material mapping based on the context (or material) of the face in the
> obj file. If you use the same set of materials in all your models you
> could create a material library and a corresponding mapping file.
> Obj2rad then assigns the correct Radiance material name (as far as I
> understand this point, never used it much).
>
I saw that. I was hoping there was a way to use the .MTL file that's already generated by Max. Basically, I'm just being lazy, and hoping there was an existing solution out there.
> You're welcome! If you can provide Radiance geometry we might offer a
> discount ... ;)
Now that doesn't sound like a bad idea! ;-)
--
Jeffrey McGrew
Because We Can, LLC
(415) 505-4689
www.becausewecan.org
------------------------------
Message: 4
Date: Thu, 11 May 2006 08:42:54 -0700
From: Jeffrey McGrew <toast at becausewecan.org>
Subject: Re: [Radiance-general] Glass & MTL file troubles... (or how
to go from Revit to Radiance with little pain...)
To: Radiance general discussion <radiance-general at radiance-online.org>
Message-ID: <44635B7E.4040609 at becausewecan.org>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Lars Grobe wrote:
> You will get nicer Renderings with lower ambient settings. But with
> big window openings, it should not be really necessary to use mkillum.
> If you use it, consider generating the faces in another tool that
> gives you more control, maybe "even" writing them with an editor.
>
'Nicer' is good, but I'm worried about the actual numbers. We want renderings as well as falsecolor images. If we just wanted nice renderings, we'd probably go to vRay, which is kind of our unofficial standard for 'sexy' images. If I can get 'ok' renderings but decent falsecolor images without having to edit the glass or use it as a lightsource I could make this whole process very, very easy.
> Triangles don't work with mkillum. Still, the obj format is not
> limited to triangles, it depends more on the modeler (and you must
> make sure that the panes are 100% plain).
>
Yeah, when I export to OBJ I'm picking the 'poly' option which seems to produce polygons and rectangles. Revit produces rectangles/polys as well, it doesn't render everything to triangles like some modelers. So I think I'm ok there.
> Do you know obj2rad's -n option?
Yeah, just being lazy, and hoping for an easy solution.
What would be the best is to use the new Revit API to write an Radiance exporter, and skip Max altogether. However, this is beyond my abilities and available time currently (and sadly).
Jeffrey McGrew
Because We Can, LLC
(415) 505-4689
www.becausewecan.org
------------------------------
Message: 5
Date: Thu, 11 May 2006 17:51:21 +0200 (MEST)
From: "Lars Grobe" <grobe at gmx.net>
Subject: Re: [Radiance-general] Glass & MTL file troubles... (or how
to go from Revit to Radiance with little pain...)
To: Radiance general discussion <radiance-general at radiance-online.org>
Message-ID: <16096.1147362681 at www111.gmx.net>
Content-Type: text/plain; charset="us-ascii"
Hi!
> That's what we've got going, it's a building with lots of glass and
> skylights and such. So do you think just having the windows be glass
> would be enough to get somewhat-close numbers? I fear that not making
> the glass a secondary light source, and just having it be, well, glass
> and only having the ray of sunlight bouncing around is going to give
> me bad numbers.
I think you are worried too much here. The numbers should not change so much because of mkillum, the image will look nicer in many cases. But the main reason for mkillum is the following.
If you have a model where most of the indirect light enters the room through small windows, the probability that the (random) indirect rays, which are send from the surface to several (random) directions to find out its indirect contribution hits the (small) light source is getting low. You can increase the number of random rays, but that won't help sometimes and takes a lot of rendering time. So, in these cases, it is better to bring the light source closer. Bt as it sounds to me, your model is not the typical case with shading devices etc, right? So, if you have simple, large windows, at least your numbers should be fine.
Lars.
------------------------------
Message: 6
Date: Thu, 11 May 2006 10:30:01 -0700
From: "Gregory J. Ward" <gregoryjward at gmail.com>
Subject: Re: [Radiance-general] water simulation
To: Radiance general discussion <radiance-general at radiance-online.org>
Message-ID: <7EC041C2-8F0F-4B87-915C-6D83E5A90A7F at gmail.com>
Content-Type: text/plain; charset=ISO-8859-1; delsp=yes; format=flowed
Hi Ignacio,
Regrettably, I don't have time to debug your function file at the moment. You can try using the debugcal script that comes with Radiance, giving it ray origins and directions on the standard input or using ximage:
ximage test.pic | debugcal test.oct -f water.cal -e '$1=dx;$2=dy; $3=dz;$4=dxx;$5=dyy;$6=dzz'
This script assigns the standard variables from rayinit.cal so you can find out what is happening.
To answer your first question, the Rdot variable is the negative dot product, meaning that it is positive when a ray strikes the front of a surface material, and negative when it strikes the back side of the surface.
Hope this helps.
-Greg
> From: Ignacio Munárriz <info at aisarquitectura.com>
> Date: May 11, 2006 5:13:43 AM PDT
>
> Thanks Greg, i think i'm near to get it, but there is something that
> is not working, i dont know if Rdot is the DOT product or the -DOT
> product, i tried the two but it is still not working, i´ve been trying
> to do some tests with calc and it seems to work but something must be
> wrong because rpict gives the aiming error, what is the best tool in
> radiance to test this kind of things, i say, testing cal files while
> sending rays
------------------------------
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