joao.tex

\documentclass{minimal}
\usepackage{pstricks}
\usepackage{pst-solides3d}
\pagestyle{empty}
 
\begin{document}
 
\begin{pspicture}(-4,-1)(4,7.5)
\psset{viewpoint=50 60 20 rtp2xyz,lightsrc=viewpoint}
\psset{solidmemory}
\pstVerb{
/mytransform {
3 dict begin
   /z exch def
   /y exch def
   /x exch def
   z 2 lt {
      x y z
   } {
      x y 4 x dup mul sub
      z min
   } ifelse
   %
end
} def
}
\psSolid[object=cylindrecreux,
   r=2 sqrt,
   ngrid=6 36,
   h=4,
   fillcolor=yellow,
   transform=mytransform,
   name=B1,
   action=none,
]
\defFunction[algebraic]{Ftest}(x,y)
   {4-x^2}
   {}
   {}
\psSolid[object=surface*,
   r=2 sqrt,
   ngrid=4 36,
   function=Ftest,
   name=A1,
   fillcolor=yellow,
   action=none,
]
\psSolid[object=fusion,
   base=A1 B1,
]
\end{pspicture}
\end{document}