In this project, we develop and apply a tactile rendering algorithm to simulate rich 3D geometric features (such as bumps, ridges, edges, protrusions, texture etc.) on touch screen surfaces. The underlying hypothesis is that when a finger slides on an object then minute surface variations are sensed by friction-sensitive mechanoreceptors in the skin. Thus, modulating the friction forces between the fingertip and the touch surface would create illusion of surface variations. We propose that the perception of a 3D "bump" is created when local gradients of the virtual bump are mapped to lateral friction forces.