1. A computer-implemented method for generating a three-dimensional modeled object that represents a physical entity, comprising: providing sample points; determining a volumetric function, within a predetermined class of volumetric functions, as the optimum of an optimization program that explores orientation vectors defined at the sample points, wherein the optimization program penalizes a distance from the explored orientation vectors, wherein the distance from the explored orientation vectors involves a difference between a gradient of an argument volumetric function and an explored orientation vector at the sample points; fitting the sample points with an isovalue surface of the volumetric function, wherein the optimization program further penalizes oscillations of the isovalue surface; and displaying the three-dimensional modeled object generated based on the fitting.