[Radiance-general] Luminaire modelling using Radiance
Jack de Valpine
jedev at visarc.com
Wed Nov 11 14:12:37 PST 2015
Hi Germán,
I am following this somewhat peripherally, however I do note that from
the appearance of your test samples, in the bottom view, the right most
sample looks different. The higher end (the yellow portion) is smaller
than in the other two samples...
-Jack
On 11/11/2015 4:07 PM, Germán Molina Larrain wrote:
> In the end, this is the illum modifier... *I wonder about the
> src_theta *parameter
>
> void brightdata noGeo_illum_dist
> 4 boxcorr noGeo_illum.dat source.cal src_theta
> 0
> 4 1 0.1 0.1 0.1 # 1, dimx, dimy, dimz
>
> 2015-11-11 17:56 GMT-03:00 Germán Molina Larrain <germolinal at gmail.com
> <mailto:germolinal at gmail.com>>:
>
> Hi Greg,
>
> Thanks very much for the information. I tried what you said, and I
> think that you might be slightly wrong.
>
> - At First I did what you said... multiplied the original A1 value
> in brightdata (127.324) by Pi and by R2 (0.05*0.05) and the
> returned number was ridiculously close to 1, which is the -m
> option I input.
>
> - I checked the surce.cal file, and the boxcorr requires A1, A2,
> A3 and A4... the first one being a multiplier and the others being
> the length, width and depth of the box. Using A1...A4 = 1 0.1 0.1
> 0.1, I got the following results
>
> TOP VIEW
> <https://drive.google.com/file/d/0B2NfkTSl19hQVkdzN1JlWFllcE0/view>
> BOTTOM VIEW
> <https://drive.google.com/file/d/0B2NfkTSl19hQVXRvTXRWYV9hR2s/view?usp=sharing>
>
> One of them is using just ies2rad , the second is using ies2rad -i
> 0.05 and the third one is transforming this to a box as explained
> before.... *THEY LOOK GOOD TO ME...?*
>
> I think the area and that kind of things has to be used for planar
> surfaces. right? I mean, for when we do crazier boxes...?
>
> Regards,
>
> Germán
>
> 2015-11-11 16:40 GMT-03:00 Greg Ward <gregoryjward at gmail.com
> <mailto:gregoryjward at gmail.com>>:
>
> Hi Germán,
>
> Yes, it is a little more complicated, and you are right to
> worry about normals! Actually, it is the projected area that
> matters, which for the sphere is (mostly) constant. The main
> thing you need to do is to compute a first real brightdata
> argument (A1) equal to the existing one produced by ies2rad,
> multiplied by PI*R*R, where R is the radius of the original
> sphere. Multiplying the value thus by the projected area of
> the emitter gets you back to radiant intensity. Then, use the
> "boxcorr" function as the first string argument to the
> brightdata primitive in order that this radiant intensity is
> divided by the projected area in the appropriate direction
> during rendering.
>
> It would be prudent to verify the results by rendering
> illuminance in a large sphere around the light source before
> and after, just to make sure neither of us messed up!
>
> Cheers,
> -Greg
>
>> *From: *Germán Molina Larrain <germolinal at gmail.com
>> <mailto:germolinal at gmail.com>>
>>
>> *Subject: *Re: [Radiance-general] Luminaire modelling using
>> Radiance
>>
>> *Date: *November 11, 2015 9:29:48 AM HST
>>
>> *
>> *
>>
>> Hello again guys,
>>
>> I have a question now.... I have been reading about all this,
>> and I would like to input geometry surrounded by illum.
>> However, ies2rad seem to only be able to generate a Sphere.
>> How do I try this with different shapes? (i.e. a box) is it
>> just a matter of deleting the Sphere and put a lot of
>> Polygons with the same modifier? I am worried about normals
>> and stuff like that.
>>
>> I hope I made myself clear, haha
>>
>> Regards,
>>
>> Germán
>>
>> 2015-08-10 10:24 GMT-03:00 Germán Molina Larrain
>> <germolinal at gmail.com <mailto:germolinal at gmail.com>>:
>>
>> well, thanks a lot guys! I have a lot to read, write, try
>> and see now.... I will let you guys know how this goes
>> and come back with a lot of new questions, haha.
>>
>> Best,
>>
>> Germán
>>
>> 2015-08-08 19:52 GMT-03:00 Randolph M. Fritz
>> <rmfritz3 at gmail.com <mailto:rmfritz3 at gmail.com>>:
>>
>> "Further to Randolph’s post, the idea is to wrap the
>> luminaire
>> geometry as tightly as possible using the shapes
>> Randolph mentioned,
>> but this enveloping geometry will have *illum*
>> applied to it, not
>> glow"
>>
>> Duh. Rob is, of course, quite correct.
>> --
>> Randolph M. Fritz, Lighting Design and Simulation
>> +1 206 390 4477 <tel:%2B1%20206%20390%204477> ||
>> rmfritz3 at gmail.com <mailto:rmfritz3 at gmail.com>
>>
>>
>> On Sat, Aug 8, 2015 at 1:59 PM, Rob Guglielmetti
>> <rob.guglielmetti at gmail.com
>> <mailto:rob.guglielmetti at gmail.com>> wrote:
>> > Thomas has great info on lamp color and using
>> replmarks. Further to
>> > Randolph’s post, the idea is to wrap the luminaire
>> geometry as tightly as
>> > possible using the shapes Randolph mentioned, but
>> this enveloping geometry
>> > will have *illum* applied to it, not glow. The glow
>> is used to illuminate
>> > the luminaire geometry itself so that it appears
>> realistic in a rendering.
>> > You apply glows to the lamp objects in the
>> luminaire generally, or you could
>> > apply them to any shades or lenses in the luminaire.
>> >
>> > The luminous intensity of the illum is derived from
>> the input lumens in the
>> > IES file and is modulated by a few cal files, which
>> use the candela values
>> > from the IES file. The lamp color utility can give
>> you reasonable values to
>> > use for the glows, based on lamp input lumens.
>> Again, the glows illuminate
>> > the local luminaire geometry, and the illums
>> actually illuminate the space.
>> > The ileum material is invisible when viewed
>> directly, which is why you need
>> > the glows to make the luminaries appear correct in
>> a rendering. The flux
>> > from the glow also does not make it past the illum
>> geometry and so it does
>> > not contribute to the scene illumination or any
>> calculations.
>> >
>> > There is some info on using illums and glows here:
>> >
>> >
>> http://www.rumblestrip.org/using-the-illum-material-for-smoother-renderings-in-radiance/
>> >
>> > I did a bunch of crap with different illum geometry
>> and cal files
>> > (lboxcorr.cal et al.) and got pretty good at
>> picking the best ones for the
>> > jobs at hand (wall mounted sconces and stuff like
>> that can be tricky to get
>> > looking “right”), but never got around to posting a
>> summary on that stuff. A
>> > good place to start is just running a few different
>> luminaire types though
>> > ies2rad and see what you get, and then play with
>> the output files from
>> > there.
>> >
>> > Are we having fun yet?
>> >
>> > -Rob
>> >
>> > From: Randolph M. Fritz <rmfritz3 at gmail.com
>> <mailto:rmfritz3 at gmail.com>>
>> > Reply: Radiance general discussion
>> <radiance-general at radiance-online.org
>> <mailto:radiance-general at radiance-online.org>>>
>> > Date: August 8, 2015 at 2:32:01 PM
>> > To: Radiance general discussion
>> <radiance-general at radiance-online.org
>> <mailto:radiance-general at radiance-online.org>>>
>> > Subject: Re: [Radiance-general] Luminaire
>> modelling using Radiance
>> >
>> > The basic technique is to wrap the visible geometry
>> of the luminaire, if
>> > any, with a glow in a simple shape that actually
>> radiates the light. The
>> > glow is transparent, so that the geometry can be
>> seen, and direct
>> > illumination does not pass through the glow, so
>> light can be used internal
>> > to the glow to give the luminaire a realistic look.
>> >
>> > The glow geometry and description may be generated
>> by ies2rad. IIRC only
>> > four shapes are supported: sphere, rectangular,
>> cuboid (box), and thin disc.
>> >
>> > Ies2rad does not support eulumdat and again, IIRC,
>> has not been updated to
>> > support the latest IES photometry standard, LM-63-02.
>> >
>> > --
>> > Randolph M. Fritz, Lighting Design and Simulation
>> > +1 206 390 4477 <tel:%2B1%20206%20390%204477> ||
>> rmfritz3 at gmail.com <mailto:rmfritz3 at gmail.com>
>> >
>> > On Sat, Aug 8, 2015 at 7:46 AM, Thomas Bleicher
>> <tbleicher at gmail.com <mailto:tbleicher at gmail.com>> wrote:
>> >> Hi German.
>> >>
>> >> The most important information you need you will
>> find in the ies2rad man
>> >> page. In general you use it to create a library of
>> luminaire *.rad and
>> >> *.dat
>> >> files which you can later reference into your
>> scenes via xform. I found it
>> >> more convenient and flexible for my exporters to
>> create files with
>> >> triangular markers and use "!replmarks ..." to
>> place multiple luminaire
>> >> files. That way you can later replace all
>> luminaires in an array with a
>> >> single change in the scene file.
>> >>
>> >> When you write a plugin you have to pay attention
>> to the units of the ies
>> >> file and adjust the -d parameter accordingly.
>> Unfortunately ies2rad
>> >> doesn't
>> >> read that information from the file.
>> >>
>> >> The geometry in IES files is limited to discs,
>> ovals, rectangles and
>> >> extrusions of these shapes. Mostly you will find
>> the 2 dimensional shapes
>> >> for recessed and spot lights while the 3
>> dimensional shapes are used for
>> >> pendants (boxes and cylinders). If you want to
>> avoid these crude things in
>> >> your model and use detailed geometry instead (from
>> a dxf file, for
>> >> example)
>> >> then you use the -i option to create an illum
>> sphere. The sphere will be
>> >> used with the luminance data generated from the
>> ies file. You have to
>> >> place
>> >> the detailed geometry of fixture into the sphere
>> yourself. ies2rad doesn't
>> >> do that for you.
>> >>
>> >> I found that geometry provided by manufacturers is
>> very detailed and can
>> >> lead to problems in large models. MGF geometry
>> information is extremely
>> >> rare.
>> >>
>> >> You can use the -t option to set the lamp type.
>> This defines the color
>> >> temperature. The -m option allows you to set a
>> maintenance factor that all
>> >> artificial lighting calculations require. Not that
>> some lamp type entries
>> >> in
>> >> the lamp.tab file already include a correction
>> factor for the lamp so you
>> >> have to take this into account when calculating
>> the final value of -m. I
>> >> found it safest to use "-t WHITE" (which does not
>> have a correction) and
>> >> lump all the efficiency reductions and maintenance
>> factors together into a
>> >> single -m value.
>> >>
>> >> European manufacturers provide are more likely to
>> provide Eulumdat file
>> >> specs for their luminairs. Sometimes they convert
>> these for you into IES
>> >> files. If you can only get LDT files you can use
>> DIALUX or something
>> >> similar
>> >> to convert the LDT to IES files. It used to offer
>> this option a few year
>> >> ago, at least. There may be other converters out
>> there, but I don't
>> >> remember
>> >> the names.
>> >>
>> >> Hth, Thomas
>> >>
>> >> On Fri, Aug 7, 2015 at 2:09 PM, Germán Molina Larrain
>> >> <germolinal at gmail.com <mailto:germolinal at gmail.com>>
>> >> wrote:
>> >>>
>> >>> Hello everyone,
>> >>>
>> >>> I think this might be a silly question, but I
>> actually have not found too
>> >>> much information on how to model luminaires using
>> Radiance... I am asking
>> >>> this because I want to add this feature to the
>> plugin I am developing.
>> >>>
>> >>> What is the recommended method for modelling
>> luminaires in Radiance? I
>> >>> intend to use IES files as input. Hopefully I
>> would also have the
>> >>> geometry,
>> >>> but I have to consider cases when this is not
>> available.
>> >>>
>> >>> I know there is an IES2RAD program, but I am not
>> quite sure how general
>> >>> it
>> >>> is. Also, I have heard about the use of illums (a
>> sphere, for example)
>> >>> that
>> >>> covers the entire luminaire....?
>> >>>
>> >>> I am kind of lost, so if someone could give me a
>> hint, I would really
>> >>> appreciate it.
>> >>>
>> >>> Also, if someone know where to find information
>> about IES files and their
>> >>> format, that would also be really helpful.
>> >>>
>> >>> THANKS
>> >>>
>> >>> Germán
>> >>>
>> >>> _______________________________________________
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>> >>
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