Re: [Brad] Help:Setting up a radiance system--brad

[Thomas Bleicher]

Hi Steve.

Providing photometry is not the most popular thing among manufacturers.
The files you get typically are years old (no problem there because the
fittings are as old or sometimes much older) and do not always conform
to the IES or Eulumdat standard.

In you particular case I'd guess that the IES file does not contain
correct luminaire dimensions and represents the fitting with a small
ball or disk for any calculation programm. Usually this is not a
problem as most (other) calculation software does not offer the same
level of control as Radiance does. In those apps it doesn't matter
where the light physically comes from.

You can use the '-g' option of ies2rad to create a separate scene file
from the mgf geometry in your file. To preview any scene file use the
'objview' script that's installed with Radiance. It takes the scene
file, places it in an illuminated environment and starts rvu with
the right view parameters. That should give you an idea of the shape
of the fitting.

How can you verify your Radiance light source?
I'd get one of the popular calculations apps (Relux or Dialux) load
the IES file into that and calculate the light distribution of a simple
box with one light fitting in it. If Radiance achieves the same
pattern and roughly the same values you can assume that you have
converted the IES file correctly.

About your last question:
Light sources that have a complex light output (like those based
on IES photometry) are created as light emitting geometry in
Radiance. You can have simple spotlights but I don't remember
if brad does create them by default.


Regards,
Thomas


On 16 Apr 2007, at 18:37, steve michel wrote:

> I used the ies2rad utility and with getbbox on the generated rad  
> file, I get  bounding box dimensions that don't correspond to the  
> lamp geometry. For example a fixture with a T8 lamp returns a  
> getbbox dimension of .1,.1,.1 (xyz). The ies file I used includes  
> mgf data and a  .dxf file was generated (via ies2rad or brad). Is  
> there a way to confirm the fixture/lamp scale and preview it???
>
>
> And in general, should the lamps loaded via brad's libraries appear  
> as lamps or geometric emitting objects? Eg.
>
> ---------------------------------------------------------------------- 
> ---------------
>
> >
> > > 3/ this issue is probably trivial for experienced users:  
> SCALING of lights
> > >
> > > If I insert a radiance ies light into a blender scene, how do I  
> check that
> > > the relative scales of blender objects AND radiance lights  
> coincide????? A
> > > room 10x 10 units in blender with an inserted light fixture  
> from radiance
> > > libraries might might too small or too big..does anyone know of  
> this and/or
> > > can explain???
> >
> >Just make sure that you use units consistently in your file.
> >For instance I always use metres.
> >So if I get a model in millimetres, I scale it down with a .001  
> factor.
> >Then ies2rad by default outputs geometry and photometries using  
> meters
> >(-dm), so I have no problems.
> >Perhaps you're trying to use the desktop radiance luminaires?
> >They are in foot, if I remember well, so you must scale them
> >appropriately, and redo the ies2rad run to get the photometries  
> right.
> >
> >HTH,
> >
> >Francesco
> >
> >
> >
> >
> >
> >
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