A modeling arrangement for modeling the topography of a three-dimensional surface, comprising: a light source (102, 200) arranged to produce substantially monochromatic and coherent electromagnetic radiation; a camera arranged to photograph the surface to be modeled at wavelengths emitted by the light source (102, 200) as well as wavelengths detected by the human eye; and a grating provided in connection with the light source (102, 200); wherein the light source (102, 200) and the grating provided in connection with the light source (102, 200) are arranged jointly to produce a diffraction pattern of a known geometry on the surface to be modeled, wherein the diffraction pattern is a pattern that accurately complies with a mathematical-physical model and wherein beam output angles of the diffraction pattern are accurately known based on the mathematical-physical model; and the modeling arrangement being calibrated, and hence having calibration information, so that the relative orientations of the optical axis of the camera and the diffraction axis are known and that the position, distance and orientation of the output point of the grating to the starting point of the optical axis of the camera are known and so that the calibration takes into account the calibration information that corrects the optical distortions of the lens of the camera, the modelling arrangement configured to calculate a depth position of each point of a network of points produced by the diffraction pattern based on a single photograph of the camera using the calibration information from the modelling arrangement, wherein the optical distortions of the photograph are corrected by the calibration information by moving the pixels of the photograph to correct positions. a light source (102, 200) arranged to produce substantially monochromatic and coherent electromagnetic radiation; a camera arranged to photograph the surface to be modeled at wavelengths emitted by the light source (102, 200) as well as wavelengths detected by the human eye; and a grating provided in connection with the light source (102, 200); wherein the light source (102, 200) and the grating provided in connection with the light source (102, 200) are arranged jointly to produce a diffraction pattern of a known geometry on the surface to be modeled, wherein the diffraction pattern is a pattern that accurately complies with a mathematical-physical model and wherein beam output angles of the diffraction pattern are accurately known based on the mathematical-physical model; and the modeling arrangement being calibrated, and hence having calibration information, so that the relative orientations of the optical axis of the camera and the diffraction axis are known and that the position, distance and orientation of the output point of the grating to the starting point of the optical axis of the camera are known and so that the calibration takes into account the calibration information that corrects the optical distortions of the lens of the camera, the modelling arrangement configured to calculate a depth position of each point of a network of points produced by the diffraction pattern based on a single photograph of the camera using the calibration information from the modelling arrangement, wherein the optical distortions of the photograph are corrected by the calibration information by moving the pixels of the photograph to correct positions.