I noticed that gensky returns constant brightness for sun altitude less than ~9 degree.
Looking at the gensky.c at line 276 suggest the same thing:
solarbr = 1.5e9/SUNEFFICACY * (1.147 - .147/(sundir>.16?sundir: .16));
Is there any reason for using a constant value for sun altitudes below a certain degree?
I can see that without doing this the formula gives negative values below a certain degree.
This discontinuity shows itself more when doing annual direct solar calculation where you would get
weird artifacts on the falsecolor image.
I tried the gendaylit command (with params for cie clear sky) and it doesn’t behave same as gensky.