Center-to-limb variation of intensity a) and polarization c) for the test model atmosphere. The solid line corresponds to the formal solution of differential radiative transfer equations for polarized light using a modified Feautrier method for spherical geometry and the dashed line shows the formal solution of integral radiative transfer equation, using the short characteristics method. The residuals between two approaches are depicted in b) and d) for the center-to-limb variation for intensity and polarization, respectively.