-5 5 setxrange -4 6 setyrange 25 setxunit 10 10 12 SetCamPos 0 0 0 SetCamView qplanxy 2 setlinejoin 10 setresolution 10 10 10 setlightsrc .1 setlinewidth .6 setgray /f { 2 dict begin /y exch def /x exch def #rpn# (x^2 + y^2)/4 end } def -4 4 -4 4 [.5 .5] {f} newsurface dup [.3 .5] solidputinouthuecolors drawsolid**