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

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________________________________

From: Giovanni Betti [mailto:gbetti@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