[Radiance-general] Luminaire modelling using Radiance

Mon Aug 10 06:24:32 PDT 2015

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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