CIE sky model not changing brightness with sun angle

[Rob Burns]

I was playing with the Vray Lightmeter today, taking some Sun and Sky illuminance measures at different times of day and noticed that the Preetham sky dims as you would expect when the sun is low, but the CIE model stays the same full brightness no matter what the sun angle is. So even when the sun angle is -5 degrees the CIE sky illuminance is 25000 lux, when it should be maybe 400 to 2000 lux. Is this a bug, or does the CIE sky just not link properly with the Vray sun? Looks like I need to stick with the preetham sky from now on.

[vlado]

No, it's not a bug; when doing lighting measurements you are supposed to manually enter the sky illuminance in the sky parameters to the desired value. I believe there are tables with the average sky illuminance for a given place and for a given time of the day.

Best regards,
Vlado

[Rob Burns]

thanks Vlado, good to know.