Segmentations of stellar surface and their performances in energy-flux integrations for a centered dipole (B_d = 10 MG, i = 45°). The magnetic-field strength in each cell is averaged using its values on the center (black circle) and vertices (red circles). Upper panel: segmentation based on spherical t-design (t = 19) and its associated Voronoi tessellation. Middle panel: segmentation constructed with equal steps in latitude and longitude. Lower panel: variation of mean squared error of emerging flux as a function of the cell number for t-design (solid lines) and constant latitude and longitude step (dashed lines) integrations and different field strengths.