\documentclass{article} \usepackage{pst-solides3d} \begin{document} \pagestyle{empty} \newcommand\SectionArenes{ 360 -20 180{ /Angle exch def R r sub 2 div Angle cos mul R r add 2 div add % y=(R-r)cos(A)+(R+r)/2 R r sub 2 div Angle sin mul neg h add % z=-(R-r)sin(A)+h } for r 0 R 0 } \begin{center} \begin{pspicture}(-5,-6)(5,5) \psframe*[linecolor=gray!20](-5,-4)(5,4) \psset[pst-solides3d]{SphericalCoor,viewpoint=50 45 45,Decran=25,lightsrc=10 20 20} \psSolid[object=grille,base=-10 10 -10 10,fillcolor=yellow!30](0,0,0) \psSolid[object=anneau,section=\SectionArenes,fillcolor=blue!50!gray!30,h=4,R=8,r=6]% \psPoint(0,0,12){Z} \psline[arrowsize=0.3,arrowinset=0.2,linecolor=blue]{->}(O)(Z) \uput[u](Z){\textcolor{blue}{$z$}} \end{pspicture} \end{center} \end{document}