l of the arrow object i e therefore the point 11 on the boundary between the point 10 and the point 12 is determined the arrowhead portion 20 is between the point 10 and the point 11 and the line portion 30 is between the point 11 and the point 12 s 20 finally the arrowhead 20 and the line portion 30 are processed respectively and connected to be an arrow object for the line portion 30 create the directional vector mapping data required by the line portion 30 within a predetermined width of the two laterals of the line portion 30 s 30 the predetermined width is assigned by the user for example the dashline portion as shown in fig3 assume that the 2 dimensional graphical data of the line portion is o and the directional vector mapping creation function is r u00b7 thus the directional vector mapping data of the line portion 30 is u03bd 1 r o the directional vector mapping data u03bd u00b7 1 of the line portion 30 capable of representing each corresponding pixel of the third axis i e z axis is created by the image effect on relation map e u00b7 to obtain the parameter on the third axis corresponding to each pixel of the line portion the image effect on relation map e u00b7 comprises the parameter of a threshold length r 1 and a contour curve for defining the change of each pixel on the third axis z within the threshold range starting from the edge fig5 a 5 c respectively represent three possible contours fig5 a is a rounded bevel shape and c 1 represents its contour fig5 b is a linear bevel shape and c 2 represents its contour and fig5 c is a combinational shape of two rounded.