Embodiments of the present invention include generating a 3D model of a body cavity, and receiving, from a position transducer associated with a medical probe configured to be inserted into the cavity and having at least one elongated electrode disposed along a distal end of the probe, signals indicating orientation and location coordinates of the distal end within the body cavity. Based on the model and the signals, while parts of the given electrode other than the identified segment are not in contact with the inner surface of the cavity, a segment along a length of a given electrode that is in contact with tissue at a site on an inner surface of the cavity is identified. A graphical representation of the model with a visual marker at a location on the model corresponding to the site contacted by the segment of the given electrode is rendered to a display.