[Radiance-general] integral of radiation in one point -spherical illuminance

[Greg Ward]

That's a really smart suggestion, David.  This didn't even occur to me, and it avoids the issue with source sampling Lars referred to earlier (April 20 post).  Guilio's idea would also work, although it might take longer to achieve similar accuracy.

Cheers,
-Greg

> From: David Geisler-Moroder <david.moroder at gmail.com>
> Date: May 9, 2012 2:23:17 AM PDT
> 
> Hi Giovanni,
> 
> did you try using rsensor?
> Using a simple sensor file with all sensor values equal to 1 such as
> 
> degrees 0 90 180 270
> 0       1  1   1   1
> 120     1  1   1   1
> 
> should do the work.
> 
> Best,
> David
> 
>  
> 
> 2012/5/9 giulio antonutto <antonutto at yahoo.it>
> Giovanni,
> 
> I think there is another way, which requires some more fiddling, but that can give you a lot more flexibility.
> Especially with visualisations.
> I would start by taking n. 6 x  90º wide angular images of luminance from the observer position.
> You could use vwrays to work with rtrace.
> Then derive the illuminance at the view point, as you know the solid angle of each pixel / direction and the luminance of it.
> See the IESNA book for details. You could write a little script with rcalc, python or octave.
> I guess Andy or Greg would do all in one line with sed / awk :-)
>  
> Once done you could have polar maps of your illuminance component, directionality of lighting in the space, etc etc.
> 
> To start playing with the idea you could do as Mark is suggesting, 6 illuminance values are  good as you could easily plot the vector illumiannce to visualise the directionality of lighting.
> This is an useful metrics for museums.
> 
> Either way, have fun!
> G
> 
> 
> On 8 May 2012, at 14:16, Giovanni Betti wrote:
> 
>> Dear Martin, Minki,
>>  
>> Thanks for the replies, I guess what I was trying to calculate (and to whom dr. Martin refers to) is better called cubical illuminance; the script Greg shared with Minki (thanks as always, Greg!) allows to sample a full sphere in one go.
>>  
>> I think I have my ideas a lot clearer now, I’ll just need to implement either one of the approaches.
>>  
>> Thanks,
>>  
>> Giovanni
>>  
>>  
>>  
>> From: Moeck, Dr. Martin [mailto:m.moeck at osram.com] 
>> Sent: 08 May 2012 12:52
>> To: 'Radiance general discussion'
>> Subject: Re: [Radiance-general] integral of radiation in one point -spherical illuminance
>>  
>> Hi Giovanni,
>>  
>> that is called spherical illuminance. As an approximation, you could calculate 6 illuminance values (up, down, East, West, North, South) and average them. Christopher Cuttle wrote a few papers on spherical illuminance.
>>  
>> Regards
>>  
>> Martin Moeck
>> OSRAM
>>  
>>  
>>  
>> From: Giovanni Betti [mailto:gbetti at fosterandpartners.com] 
>> Sent: Tuesday, May 08, 2012 1:42 PM
>> To: Radiance general discussion
>> Subject: [Radiance-general] integral of radiation in one point
>>  
>> Dear list,
>>  
>> I have question that I hope you’ll help get my head around.
>> I want to calculate the overall illuminance on a point in space that is, regardless of directionality.
>> I have made some simplified 2d sketches for clarity.
>> As I understand a radiance sensor point in rtrace will have cosine related sensitivity (image01)
>> If I am to place two coincident with opposing normals (image2) I’ll miss on contributions from the sides.
>> Rotating the normals by 90 degrees at a time (figure 3) and summing contributions might not work either because will overestimate diagonal contributions (figure 4 ).
>> So I’m not getting too much closer to the solution…
>>  
>> Is there something that I am missing here?
>> Any light on this will be appreciated,
>>  
>> Best,
>> Giovanni Betti
> 
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