%@AUTEUR: Juergen Gilg
% \section*{Twister \dots}
\psset[pst-solides3d]{viewpoint=10 9 10,SphericalCoor,
	Decran=80,lightsrc=5 -5 5}
\begin{pspicture}(-6,-6)(-6,6)
\rput(0,0){
\defFunction[algebraic]{twister}(u,v){cos(u)*cos(v)*(abs(cos(3*u/4))^1 
    + abs(sin(3*u/4))^1)^(-1/1)*(abs(cos(6*v/4))^1 + abs(sin(6*v/4))^1)^(-1/1)}%
{sin(u)*(abs(cos(3*u/4))^1 + abs(sin(3*u/4))^1)^(-1/1)}%
{cos(u)*sin(v)*(abs(cos(3*u/4))^1 + abs(sin(3*u/4))^1)^(-1/1)*(abs(cos(6*v/4))^1 + 
    abs(sin(6*v/4))^1)^(-1/1)}
\psSolid[object=surfaceparametree,
    base=pi neg 2 div  pi 2 div  0 pi 2 mul,
    linecolor={[cmyk]{1,0,1,0.5}},linewidth=0.75\pslinewidth,
    ngrid=45,
    RotY=90,
    RotZ=90,
    function=twister]%
}
\end{pspicture}