A method, including, receiving three-dimensional tomographic data with respect to a body of a living subject, and using the data to generate a representation of an external surface of the body and displaying the representation on a screen. The method further includes inserting an invasive instrument into a region of the body and identifying a position of the instrument in the body. The method also includes rendering an area of the external surface surrounding the identified position of the instrument locally transparent in the displayed representation, so as to make visible on the screen an internal structure of the body in a vicinity of the identified position.
