%% Auteur : Manuel Luque
%%
\begin{pspicture}(-3,-3)(4.5,5)
\psset{SphericalCoor,lightsrc=viewpoint,viewpoint=100 10 10,Decran=100}
\psSolid[object=grille,base=-4 4 -3 3,linecolor={[rgb]{0.72 0.72 0.5}},action=draw](0,0,-2)
\defFunction[algebraic]{G1}(t){t}{0.25*t^2}{-2}
\defFunction[algebraic]{G2}(t){-t}{-0.25*t^2}{2}
\psSolid[object=courbe,
   function=G1,
   range=-3 3,
   r=0,
   linecolor=blue,
   linewidth=2pt]
\psSolid[object=cone,
   function=G1,
   range=-3 3,
   ngrid=3 16,
   incolor=green!50,
   fillcolor=yellow!50,
   origine=0 0 0]
\psSolid[object=courbe,
   function=G2,
   range=-3 3,
   r=0,
   linecolor=blue,
   linewidth=2pt]
\gridIIID[Zmin=-2,Zmax=2,spotX=r](-4,4)(-3,3)
\end{pspicture}