[Radiance-general] Guidelines for trans Material

[Marcus Jacobs]

Thanks

Although I would like to avoid the time and expense of performing this 
analytical work, I am thinking that it may be necessary. First, is there any 
existing data that is readily available for translucent materials that are 
used as diffusing elements for light fixtures? Also, are there any 
specifications or procedures as to how to perform these tests?

Thanks

Marcus


>>From: Jack de Valpine

>Just to add to what Rob said. I know that it is possible to arrange for
>equipment rentals directly from KonicaMinolta. This especially makes
>sense for the luminance meter which is indeed ~$3,000 at retail. Also on
>the spot light that Rob mentioned, good camera equipment stores that are
>set up to provide rental equipment to professionals will have a wide
>selection of lighting. I know that for one exercise I rented a small
>spotlight where you could adjust the beam spread (sorry I do not
>remember the name/type) at a reasonable price.
>
> >
> > On Jun 3, 2006, at 8:30 AM, Marcus Jacobs wrote:
> >> So I think they are actually more complicated that the example that I
> >> showed to you before. Out of curiosity, just as many modeling
> >> software estimate a complex surface as a mesh of planes or triangles,
> >> could the same principle be used for the lighting fixtures
> >> themselves. In other words, instead of seeing each fixture as a
> >> single complex surface, can it be considered it as just a group of
> >> flat planes? One item that I need to have addressed is whether I
> >> should model the diffuse shades a single surface or if it acceptable
> >> to have inner and outer surfaces (you can think of it as having a
> >> thickness to it). See here:
> >>
> >> http://i35.photobucket.com/albums/d178/marcdevon/luminaireview.jpg
> >
> > Hi Marcus,
> >
> > Without actual photometric data (such as an ies file) to apply to your
> > group of flat planes, you have to model the actual comple geometry.
> > But I'm afraid I may have misunderstood your question.  As for the
> > single/dual surface question, I guess it depends on how close your
> > views will bring you to the shade.  The trans material is infinitely
> > thin, and it'd be best to model the thng as a single surface.  For
> > closeup work, you may need to introduce thickness but that's gonna get
> > a lot more complicated from a valid material definition standpoint.
> >
> >
> >>
> >>
> >> The information in Rayfront's user manual and pages 325-326 from RwR
> >> were VERY useful to me in gaining insight as to how Radiance treats
> >> light. There was a word that was mentioned that has me worried.
> >> Measure. Aside from not having any experience with performing a
> >> empirical test of light distribution, measuring light sounds very
> >> expensive. May I ask, would purchasing the needed equipment require a
> >> second mortgage to be taken out or giving up one's first born? Is it
> >> required to use transfunc or transdata in lieu of trans to obtain
> >> acceptable accuracy?
> >
> > Mmmm, measurements, yeah.  The gear can be expensive.  Let's see, at
> > my old job, where I did these measurements, I used an illuminance
> > meter, a luminance meter and a theatrical spotlight (ETC Source Four
> > HID, aka "leko", or ERS).  The light fixture was a free sample, but
> > you could use other sources too.  The illuminance meter (Minolta
> > Somethingorother-nowdiscontinued) was about $800 and the luminance
> > meter (Minolta LS-100) was more expensive, I believe almost three
> > thousand USD.  Actually, here are a couple of links I just found for
> > the meters I used (the illuminance meter I link to here is a newer
> > model than I used, but it's basically the same thing).
> >
> > http://www.tequipment.net/MinoltaTL1.asp
> > http://www.tequipment.net/MinoltaLS100.asp
> >
> > It's expensive not to mention time-consuming, but it's also fun and is
> > an excellent example of the power of Radiance, in that Radiance is
> > happy to accept material data as complex as you are willing to gather.
> >
> > Maybe Peter can chime in with his thoughts on this stuff, and maybe an
> > update on his goniophotometer project?
> >
> > - Rob
> >
> > _______________________________________________
> > Radiance-general mailing list
> > Radiance-general at radiance-online.org
> > http://www.radiance-online.org/mailman/listinfo/radiance-general
> >
> >
>
>--
># Jack de Valpine
># president
>#
># visarc incorporated
># http://www.visarc.com
>#
># channeling technology for superior design and construction
>