ex_4.tex

\documentclass[a4paper]{article}
\usepackage{pst-solides3d}
\pagestyle{empty}
\begin{document}
 
%@AUTEUR: Juergen Gilg
% \section*{Twister \dots}
\psset[pst-solides3d]{viewpoint=10 9 10,SphericalCoor,
	Decran=20,lightsrc=5 -5 5}
\begin{pspicture}(-6,-6)(-6,6)
\rput(0,0){
\defFunction[algebraic]{twister}(u,v){cos(u)*(4*sqrt(1-v^2)*sin(abs(u))^abs(u))}%
{v}%
{sin(u)*(4*sqrt(1-v^2)*sin(abs(u))^abs(u))}
\psSolid[object=surfaceparametree,
    base=pi neg  pi  1 neg  1,
    linecolor=red!50,
    linewidth=0.75\pslinewidth,
    fillcolor=red,
    incolor=red,
    ngrid=60,
    RotY=90,
    RotZ=90,
    function=twister]%
}
\end{pspicture}
 
\end{document}