Circular polarization test case from P17 using the spheroidlike Müller matrix (Eq. (46)) with assumed orientation of the particles along the z-axis. We show the intensity I, Stokes U/I and Q/I, the linear polarization degree and angle, and the circular polarization V/I. The analytic solution is indicated by the dashed lines in black and the MCPOL model results in red and orange. For the circular polarization we also plot the difference from the analytical solution in the lower panel. The absolute difference is shown in blue and a relative difference of σ (∆(x)) = ±3 × 10⁻⁴ (Eq. (50)) is shaded in grey.