\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}