Indeed, direct normal and diffuse horizontal irradiance are the two fields taken from the EPW file.
Sky cover is not used at all. (Any change in results is merely stochasticity.)
I'm guessing that you are hoping to separate direct and diffuse sources by manipulating the EPW file. I would advise against this. Radiance and Daysim use the ratio of direct and diffuse irradiance to determine the distribution of light over the sky dome. So removing the direct component won't merely remove the sun -- it will dramatically (and unrealistically) alter the appearance of the rest of the sky as well.
Direct and diffuse sources can be separated, but not through the current DIVA UI.
Thank you for your insightfull reply. I am indeed trying to separate these sources, but I obviously don't know much about the way in which illuminance values are calculated.
I am a student in Architecture, and hoped to be able to retrieve this kind of light information from a user friendly interface like DIVA. Apparently, it is not that simple.
Do you have any suggestions on how to do this?
Do I have to use the visual basic component for this?
Or can I better just learn how to work with Radiance directly?
I am new to these programs, so it will probably take a while for me to figure out how to do this. However, it would be nice to know where to start.
Thanks in advance,