represent entrance and exit points with respect to the ray 304 the 3 dimensional edit point 307 is constructed by taking the midpoint between the entrance point 305 and exit point 306 embodiments of the present disclosure have advantages relative to prior art methods in particular to the method described by igarashi et al in the siggraph 99 article u201c teddy a sketching interface for 3d freeform design u201d for example embodiments of the present disclosure will work with an object having any arbitrary shape embodiments of the present disclosure also enable the user to specify the clipping surface or plane with the selection of a single point the method described by igarashi et al on the other hand requires two points and the object oriented precisely relative to the single point perspective embodiments of the present disclosure also enable the user to select the single edit point from either a 2 dimensional or 3 dimensional representation of the object to be edited in an exemplary embodiment a graphical user interface presents the operator of the system 2 dimensional slice presentation of the ct voxel data and a 3 dimensional view of the segmented anatomy region of interest the operator then can choose between the 2 dimensional and 3 dimensional view for the selection of the edit point while the present disclosure includes descriptions of various preferred embodiments it should be understood by those having skill in the art that the descriptions herein are merely exemplary and that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention therefore it is intended that the invention not be limited to the best mode of carrying out this invention or to.