[Radiance-general] Luminaire modelling using Radiance

Wed Nov 11 13:07:20 PST 2015

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>:

> 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>:
>
>> 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>
>>
>> *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>:
>>
>>> 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>:
>>>
>>>> "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 || rmfritz3 at gmail.com
>>>>
>>>>
>>>> On Sat, Aug 8, 2015 at 1:59 PM, Rob Guglielmetti
>>>> <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>
>>>> > Reply: Radiance general discussion <
>>>> 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
>>>> >>
>>>> > 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 || rmfritz3 at gmail.com
>>>> >
>>>> > On Sat, Aug 8, 2015 at 7:46 AM, Thomas Bleicher <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>
>>>> >> 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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