Error in custom sky using azimuth, altitude, epsilon, delta

Hello,

I’m conducting a series of daylight simulations and in each case the sky is generated using different combinations of azimuth and altitude angles, epsilon, and delta values. I want to stick to using these four values. For some combinations, the sky is created fine, but not for others. My altitude angles range between 0-90, azimuth_0-360, epsilon_1-12, delta_0.01-0.6.

Although I’m using Honeybee to generate the skies and run the simulations, when the gendaylit command is run with the settings in the Grasshopper file the following output is seen. I posted this query in the ladybug forum and was told I might have better luck here.

Can someone help me understand why sometimes the sky is not being created? Below is what happens in such cases. You can see the hdr image for the sky is not generated and the error says Bad Radiance Image.

Hi Manal,

I am not familiar with the gendaylit -P option or its behavior, but this is clearly the source of your troubles. The gendaylit man page refers to the paper:

Solar Energy Vol. 44, No 5, pp. 271-289, 1990

in reference to the Perez parameterization. Perhaps you could discover more there? Most users apply one of the irradiance (-W or -G) or illuminance (-L) options to specify light levels. In your example, gendaylit sets the light levels (direct and indirect) to zero, probably due to the exception mentioned in the warning output.

I’m sorry I can’t be more help – there are others who understand gendaylit much better than I do.

Best,
-Greg