A method, including constructing a simulated surface of a body cavity, and pressing a distal end of a probe against a wall of the body cavity. While pressing the distal end against the wall, position measurements are accepted from the probe indicating a position of the probe within the body cavity, and force measurements are accepted from the probe indicating a force between the distal end and the wall. A distortion in the simulated surface is created at the position indicated by the position measurements, so as to form a distorted surface, upon detecting that the force measurements exceed a predefined amount. The distorted surface is then displayed.
