[Radiance-general] Luminaire modelling using Radiance

Wed Nov 11 11:29:48 PST 2015

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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