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

[David Geisler-Moroder]

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<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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