“…∇u |∇u| = 0, (1.1) as well as its nontrivial generalizations, is used in the applications as the motion of interfaces (free boundaries) in thermomechanics (solidification, crystal growth) and computational fluid dynamics (free surface flows, multi-phase flows of immiscible fluids, thin films), the smoothing and segmentation of images and the surface reconstructions in the image processing, computer vision and computer graphics (see e.g. [32,29,2,1,6,19,31,15,17]), and in many further situations related to the motion of implicit curves or surfaces. On the other hand, the convergence of numerical schemes to unique viscosity solution [9,14,7] of equation (1.1) is often an open problem, it is an exception to find an analysis of convergence of the methods used for solving the curvature driven flows in the level set formulation.…”