Schematic of the numerical calculation of planetary phase variation for an ellipsoidal and a spherical planet. Top: planet flux map for an ellipsoidal planet at transit (left), quadrature (middle), and eclipse (right) phases. The projected area of the planet changes with the number of pixels at each phase given as npix. Middle: same as top panels, but for a spherical planet. Bottom: planet flux variation obtained from integrating the flux map at the different phases. The black and red circles indicate the integrated flux value at each illustrated phase for the ellipsoidal and spherical planets, respectively.