Source PostScript (qplan.pps)

%% trace un quadrillage du plan XY
/qplanxy { 
gsave
   190 255 div 190 255 div 200 255 div setrgbcolor
   xmin3d 1 xmax3d {
   1 dict begin
     /i exch def
     [i ymin3d 0 i ymax3d 0] ligne3d
   end
   } for
   ymin3d 1 ymax3d {
   1 dict begin
     /i exch def
     [xmin3d i 0 xmax3d i 0] ligne3d
   end
   } for
grestore 
} def

%% trace un quadrillage du plan XZ
/qplanxz { 
gsave
   190 255 div 190 255 div 200 255 div setrgbcolor
   xmin3d 1 xmax3d {
   1 dict begin
     /i exch def
     [i 0 zmin3d i 0 zmax3d] ligne3d
   end
   } for
   zmin3d 1 zmax3d {
   1 dict begin
     /i exch def
     [xmin3d 0 i xmax3d 0 i] ligne3d
   end
   } for
grestore 
} def

%% trace un quadrillage du plan YZ
/qplanyz { 
gsave
   190 255 div 190 255 div 200 255 div setrgbcolor
   ymin3d 1 ymax3d {
   1 dict begin
     /i exch def
     [0 i zmin3d 0 i zmax3d] ligne3d
   end
   } for
   zmin3d 1 zmax3d {
   1 dict begin
     /i exch def
     [0 ymin3d i 0 ymax3d i] ligne3d
   end
   } for
grestore 
} def