Phase: RAMIIVTotal transmission at lower boundary level for direct illumination only
ftran_tot_dir for HET14_WCO_000_00 testcase.
ftran_tot_dir for HET14_WCO_000_20 testcase.
ftran_tot_dir for HET14_WCO_000_50 testcase.
ftran_tot_dir for HET14_WCO_090_20 testcase.
ftran_tot_dir for HET14_WCO_090_50 testcase.