Computer-implemented method for designing a CAD modeled object in a CAD system comprising a graphical user interface adapted for designing a CAD modeled object, the CAD system being history based and the CAD modeled object being described by history data and a boundary representation (B-rep), wherein the method comprises: - displaying several three-dimensional parametric shapes that constitute specifications of the modeled object in the GUI on a screen, a parametric shape being a non-uniform rational B-spline of the B-rep, a parametric shape being modeled by at least one function of at least one parameter that provides the position of points of the shape, wherein each of the displayed several three-dimensional parametric shapes is divided in several portions, the several portions including at least three portions, the portions being parts of the shape that form the shape when assembled, a different design operation being assigned to each portion; - user-interacting with the GUI on the screen through a touchpad or a sensitive screen, the user-interacting comprising a triggering and a moving of a pointer, which are projected onto a location on a support, the location of the user-interacting being a location of the pointer on the support at the triggering - determining one portion based upon the location of the projection of the user-interacting on the support, the determining being performed among all the portions; and - performing, on the shape to which the determined portion belongs, the operation assigned to this portion; wherein: ▪ the three-dimensional parametric shapes comprise a central portion, to which a moving operation is associated, at least one extremity portion, to which an extension operation is associated, and at least one intermediate portion, between the extremity portion and the central portion, to which an expansion operation is associated; ▪ the determined portion is evaluated to be at a smallest distance on the support from the location of the user-interacting among all the portions; ▪ the determining comprises evaluating a distance on the support from the projection of the location of the user-interacting to all the portions, and selecting the portion at the smallest distance from the location of the user-interacting; and ▪ the distance from the location of the user-interacting to a respective portion is a minimum of distances from the location of the user-interacting to points associated to the respective portion; and ▪ wherein the points associated to the respective portion comprise shape points which are determined by discretizing the shape and then projecting the discretized shape on the support ▪ wherein the support is a drawing surface other than the screen plane. - displaying several three-dimensional parametric shapes that constitute specifications of the modeled object in the GUI on a screen, a parametric shape being a non-uniform rational B-spline of the B-rep, a parametric shape being modeled by at least one function of at least one parameter that provides the position of points of the shape, wherein each of the displayed several three-dimensional parametric shapes is divided in several portions, the several portions including at least three portions, the portions being parts of the shape that form the shape when assembled, a different design operation being assigned to each portion; - user-interacting with the GUI on the screen through a touchpad or a sensitive screen, the user-interacting comprising a triggering and a moving of a pointer, which are projected onto a location on a support, the location of the user-interacting being a location of the pointer on the support at the triggering - determining one portion based upon the location of the projection of the user-interacting on the support, the determining being performed among all the portions; and - performing, on the shape to which the determined portion belongs, the operation assigned to this portion; ▪ the three-dimensional parametric shapes comprise a central portion, to which a moving operation is associated, at least one extremity portion, to which an extension operation is associated, and at least one intermediate portion, between the extremity portion and the central portion, to which an expansion operation is associated; ▪ the determined portion is evaluated to be at a smallest distance on the support from the location of the user-interacting among all the portions; ▪ the determining comprises evaluating a distance on the support from the projection of the location of the user-interacting to all the portions, and selecting the portion at the smallest distance from the location of the user-interacting; and ▪ the distance from the location of the user-interacting to a respective portion is a minimum of distances from the location of the user-interacting to points associated to the respective portion; and ▪ wherein the points associated to the respective portion comprise shape points which are determined by discretizing the shape and then projecting the discretized shape on the support ▪ wherein the support is a drawing surface other than the screen plane.