A method of modifying a substrate formed of non-deformable material is disclosed. In some embodiments, techniques are disclosed for identifying a region of a planar substrate that is susceptible to stretching during a subsequent shaping operation. In some embodiments, techniques are disclosed for adding an amount of non-deformable material to the planar substrate at an identified location and in a single operation, acting on the substrate until the substrate has a shape corresponding to a uniform thickness and a three-dimensional curvature.