\documentclass{article} \usepackage{pst-solides3d} \begin{document} \pagestyle{empty} \newcommand\SectionJante{ 90 10 270{ /Angle exch def R r sub Angle cos mul R add % y=(R-r)cos(A) + R R r sub Angle sin mul % z=(R-r)sin(A) } for R h 2 div neg % (y=R, z=-h/2) R h 2 div neg h 6 div add % (y=R, z=-h/2+h/6) 270 -10 90 { /Angle exch def R r sub h 6 div sub Angle cos mul R add % y=(R-r-h/6)cos(A)+ R R r sub h 6 div sub Angle sin mul % z=(R-r)-h/6sin(A) } for } \begin{center} \begin{pspicture}(-5,-4)(5,4) \psframe*[linecolor=blue!20](-5,-4)(5,4) \psset[pst-solides3d]{SphericalCoor,viewpoint=70 40 30,Decran=25,lightsrc=100 30 100} \psSolid[object=anneau,section=\SectionJante,h=8,R=12,r=8]% \end{pspicture} \end{center} \end{document}