I'm running a Radiance day-lighting calculation and I can't understand why I receive the result below when comparing the day-lighting for Dec 28 13:00 and Dec 24 at 13:00 when the direct Normal Illuminances are so different (taken from the epw file).
Furthermore I receive similar results even when the direct normal illuminance is zero, see below
I suppose what I am missing is the actual equations that Radiance uses to calculate the lux value of a point in time, we would ultimately like to do hand calculations for one point in time to quality check our simulated values. Would anyhow be able to point me to where I could find the equations and an explanation of them?
Many thanks,
