I would like to bring this subject up from it's grave because I'm having the same problem. More bounces gives lower results which is just plain wrong in my world. I can't really trust my results at the moment because they differ a lot depending on how many bounces I choose.
I tested with the solution provided, calculate as illuminance and it seems to work fine, the more bounces the higher the illuminance. But when I divide by 20769 I get quite low DF results, a little bit too low in my opinion. Btw, the formula is in my version of Ecotect is "V * 1,05", not "V * 100" as in yunpengs response, therefore I divided with 207,69 instead.
Does someone have a solution to this? Is the formula correct?
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