[Radiance-general] Luminaire modelling using Radiance

[Randolph M. Fritz]

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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