Abstract: A method of identifying spherical objects in a digital image is provided. The image comprises a plurality of 3D surface points. The method includes computing, at each point in a domain of the image, a gradient of the image; computing an elementary structure tensor at each point in the domain of the image; determining a structure tensor for each point in the domain of the image; finding the eigenvalues of the structure tensors; and calculating an isotropy measure for each structure tensor, wherein said isotropy measure is defined by a ratio of a smallest eigenvalue of said structured tensor by a largest eigenvalue of said structure tensor, wherein a spherical object correspond to an isotropy measure equal to unity.