%@AUTEUR: Juergen Gilg
% \section*{Twister \dots}
\psset[pst-solides3d]{viewpoint=10 9 10,SphericalCoor,
	Decran=10,lightsrc=5 -5 5}
\begin{pspicture}(-6,-6)(-6,6)
\rput(0,0){
\defFunction[algebraic]{twister}(u,v){-u^3/3+u*v^2}%
{u^2-v^2}%
{v-v^3/3+v*u^2}
\psSolid[object=surfaceparametree,
    base=2 neg  2  2 neg  2,
    linecolor={[cmyk]{1,0,1,0.5}},linewidth=0.75\pslinewidth,
    ngrid=50,
    RotY=90,
    RotZ=90,
    function=twister]%
}
\end{pspicture}