 segment is:

                   vrtces[1,1]      segment_vertex_set(1, start)
                   vrtces[2,1]      segment_vertex_set(2, start)
                   vrtces[3,1]      segment_vertex_set(3, start)
                     ...             ...
                   vrtces[1,n]      segment_vertex_set(1, start+n-1)
                   vrtces[2,n]      segment_vertex_set(2, start+n-1)
                   vrtces[3,n]      segment_vertex_set(3, start+n-1)

                The vertices are expressed in the body