[pstricks] I need a little help

[Cyrille Piatecki]

With pstricks-solid3D I have some little problems I am not able to find 
the  answer by myself. Thoses problems are associated with the file here 
uhder

\documentclass{article}
\usepackage{pst-solid3D}

\begin{document}
  \begin{center}
  \psset{unit=1}
  \psset{lightsrc=viewpoint }
  \psset{viewpoint=40 30 560 rtp2xyz,Decran=20}
  \begin{pspicture}(-4,-4)(4,4)
\psgrid
  \psSurface[fillcolor=cyan!10,algebraic,%axesboxed,
  ngrid=.25 
.25,incolor=yellow,linewidth=0.125\pslinewidth,grid,intersectionplan={
  [0 0 1 -5.8]
  [0 0 1 -0.35]
  },
  intersectioncolor=(bleu) (rouge),
  intersectionlinewidth=1  1,
  intersectiontype=0,](-3,-3)(5,5){-((x-4)^2+(y-4)^2)*0.2+10}
  \axesIIID[linecolor=blue,linewidth=0.4pt,labelsep=18pt](0,0,0)(11,7,7)
\psLineIIID[linecolor=blue,
  linewidth=0.1pt,linearc=0.,
  doubleline=false](0,0,0)(4,0,0)(4,4,0)(4,4,8)
\psLineIIID[linecolor=blue,
  linewidth=0.1pt,linearc=0.,
  doubleline=false](0,0,0)(0,4,0)(4,4,0)
\psLineIIID[linecolor=red,
  linewidth=0.1pt,linearc=0.,
  doubleline=false](0,0,0)(2,0,0)(2,2,0)(2,2,2)
\psLineIIID[linecolor=red,
  linewidth=0.1pt,linearc=0.,
  doubleline=false](0,0,0)(0,2,0)(2,2,0)

\pscurve[linecolor=green](-0.32,0.45)(-0.33,.9)(-0.6,2.4)
\rput(-1.8,-.2){\tiny $x_1$}
\rput(-1,-.1){\tiny $x_0$}
\rput(.8,-0.2){\tiny $y_0$}
\rput(1.2,-.5){\tiny $y_1$}
\rput(-2.5,.4){\tiny $U_0$}
  \end{pspicture*}
  \end{center}

\end{document}


1) if you look at the two \psLineIIID command they end in (4,4,8) and 
(2,2,2). The last 8 and 2 are the altitudes at wioch I want a level 
curve. They are the evaluation of the 3D plotted
function for x = y = 4 and x = y = 2. But when I have plotted the level 
curve with intersectionplan={
  [0 0 1 -5.8]
  [0 0 1 -0.35]
  },
   which give, if I have understood, an horizontal plan at the level 5.8 
and 0.35, I have been obliged to use those values and not the original 
values which give not the right level.

2) I wonder how to rotate the complete figure

3) How to erase the curve under z= - 2 without changing the présentation 
of the function.

4) How to construct really the green curve on the curvature of the curev ?
Thanks to anybody who could help me.

Cyrille Pi