Direct Sun positions in Daylight Coefficient Calculation in Daysim



What is the latest number of direct contributions that Daysim considers?
It used to be 65, and then 2305. Are all the sun-positions considered now?
I can run a simulation and find this out from .dc file I believe, but I thought I should ask instead.


I dont think 2305 was ever accessible through a GUI in any of the flavors of Daysim (despite the 2008 proposal). You can find the number of suns generated by your version of Daysim in a file called direct_radiance_file.tmp.rad in the daysim project directory. I checked mine (from a project a few months ago and it has 63 suns. direct_radiance_file.tmp.rad (7.1 KB)


Thanks for responding Sarith. I just ran a study and I see 213 columns in .DC file. So that is 65 direct sun positions. I also checked the file you mention. Again, 65 suns are there. This makes me wonder why do you have 63?


The original Daysim generates suns as per the the sunpath for a particular location, so it will keep deviating by a few suns. We do the same thing with HB[+], but take the full number of suns instead.

The 2008 DDS method and all the LBNL recommended methods such as 5 and 6 phase do away with this variability by setting 2305 (or 5165) suns irrespective of location. So, you can use the same model with different weather data without having to re-calculate the coefficient matrices.