Huh, same trouble here, I don't know where to get the calculation results of view factors.
In my thermal analysis to a radiative heating problem (with an assembly consisting of 15 parts), SolidWorks took 17h:3m:10s to finish the calculation of view factor! My computer has 24GB RAM space, however, the maximum usage of RAM space was less than 2GB. (Right now, the calculation of temperature distribution is just kicked in with only 1.10936GB memory usage.
It looks like using open system is more efficient.
view factors are calculated the standard way you calculate them for a hand calc for radiation. it is based on the overlapping area.
last time i looked there were charts that said things like plate to plate facing each other view factor is X
in solidworks simulation, the software handles all the view factor calculations between surface to surface which is what takes time at the start, especially if your mesh is really fine. you should only need to specify for surface to ambient.
the use of an open system may or may not be more efficient. but should only be changed if it is appropriate.