I am confused about rtrace options setting for mkillum command. I want to calculate the indoor illuminance on the working plane under different daylight conditions. I am wondering should give the same setting for the rtrace options of mkillum and for the rtrace options which will as input of rcalc.
For example, for the working plane illuminance prediction, I used the following commands.
So to keep accurate illuminance prediction, should I also set -ab 3 for the rtrace options of mkillum ? Whether or not it must keep these two settings the same.
Based on my tests, for glass windows, there is no difference in the indoor illuminance values with or without using mkillum to convert the window to a secondary lighting source.
The mkillum command is most useful for generating images at a particular point in time. There is little benefit to using it for interior illuminance calculations, as you will need to trace even more rays with mkillum, and may suffer some geometric approximation errors in the process.
The fact that you got similar results is actually a sign that you did both calculations correctly – though far from a guarantee.
To answer your first question, you should have one more ambient bounce in the straight rendering than you do with mkillum, since mkillum is effectively replacing one of the indirect components.