A method for controlling a graphical interface includes: calculating coordinates of a permanent magnet and direction of magnetic moment of the permanent magnet from magnetometer measurements; matching dimensions of a three-dimensional object with the calculated coordinates by multiplying each dimension of the three-dimensional object by a coefficient to obtain a three-dimensional object brought to scale and by multiplying the calculated coordinates by inverse of a coefficient to obtain scaled coordinates; constructing a two-dimensional image corresponding to the image of the object brought to scale observed from a viewpoint and along an optical axis deduced from the scaled coordinates and from the direction of the magnetic moment of the permanent magnet; and controlling the graphical interface to display the constructed image on this graphical interface.