Incorrect solid angle in gendaylit diffuse normalization factor?

Hello,

I’m looking at the Radiance source code from 2019 ( [https://github.com/NREL/Radiance/blob/master/src/gen/gendaylit.c] ), particularly the gendaylit function.

To get the normalization factor for diffuse light, integ_lv multiplies a buffer by (2*pi/144).

It seems like the buffer should be multiplied by the solid angle represented by each of the 145 azimuth and zenith angles (phi_o, theta_o) . Given that there are 145 distinct points for which the luminance is calculated (and 145 equal solid angles), I’m wondering if this value should be (2pi/145) rather than (2pi/144).

Can anyone say whether this has been changed since 2019? Or if it is in fact correct as 144?

Grateful for any help. Apologies if this has already been discussed elsewhere.

Thanks,

Annie

I don’t know the answer to this, but @Jan_Wienold might be able to help.

1 Like

Hi Anni and Greg,

This part of the code was never touched since it was released from J-J.
Delaunay in 1994.

I don’t have so much time to check the code in detail, but from a quick
look it seems you are right and this looks like a bug in gendaylit.

OK, I’ve updated the source to correct the factor, which will have a 0.7% effect on the sky normalization.

1 Like

Great! Thanks very much for your responses Greg and Jan.