% --- start of displayed preamble in the book --- input featpost3Dplus2D % --- end of displayed preamble in the book --- defaultfont:="ptmr8r"; warningcheck:=0; beginfig(1) color gammacnt; numeric newradius,radius,aux,i,numc,foc,lc; path conepath, latpath; pen thickp; f:= (2,3,4); viewcentr:= 1.5*(1,1,1); Spread:= 200; Shifts:= 300; radius= 0.5; numc= 9; thickp= pencircle scaled .5; pickup thickp; tropicalglobe(numc,black,radius,blue); for i=1 upto numc: % longitudes aux:= (i-1)*180/numc; gammacnt:=(cosd(aux),sind(aux),0); draw spatialhalfcircle (black,gammacnt,radius,true); endfor; endfig; end;