a probe, comprising:

an insertion tube having a distal end configured for insertion into a body cavity of a living subject;

a basket assembly comprising multiple resilient spines coupled to the distal end of the insertion tube and joined together in a predefined form when the basket assembly is unconstrained by external forces; and

a force sensor configured to output an indication of a force exerted on the basket assembly upon physical contact of some of the spines on an external member; and

a processor, configured to receive the indication of the force, to compute a constrained form of the basket assembly, different from the predefined form, responsively to the force, and to render to a display a graphical image representing the constrained form of the basket assembly.