[Radiance-general] Guidelines for trans Material

[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
>
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>

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# Jack de Valpine
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