1. A method of generating a descriptor of a three-dimensional object represented by a set of coordinates, said descriptor being a string of interaction values V i of one or more properties, represented by value Vb, at chosen coordinates within said set of coordinates of said three-dimensional object, with one or more properties, represented by value Vc, of the interaction points of a cage surrounding said three-dimensional object said method comprising performing for each of a set of one or more of said cages the steps of: (i). enclosing entirely said three-dimensional object in said cage, (ii). for each property, while keeping said three-dimensional object entirely enclosed in said cage by varying one or more dimensions of said cage, minimizing the interaction value V i resulting from the interaction between said three dimensional object and said cage by changing the relative orientation between the three-dimensional object and said cage, and (iii). assigning each of the obtained minimized interaction values V i to a distinct position in said descriptor.