[Radiance-general] RE: Radiance and EcoTect
John An
ja at a10nyc.com
Sun May 14 05:37:53 CEST 2006
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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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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