%% 
%%  A DANTE-Edition example
%% 
%%  Example 23-05-55 on page 388.
%% 
%%  Copyright (C) 2011 Herbert Voss
%% 
%%  It may be distributed and/or modified under the conditions
%%  of the LaTeX Project Public License, either version 1.3
%%  of this license or (at your option) any later version.
%% 
%%  See http://www.latex-project.org/lppl.txt for details.
%% 
%% 
%% ==== 
% Show page(s) 1
%% 
\documentclass[]{article}
\pagestyle{empty}
\setlength\textwidth{375.57637pt}
\setlength\parindent{0pt}

\usepackage{pstricks,pst-3dplot,pst-grad}
\def\func{x dup mul y dup mul 2 mul add x 6 mul sub y 4 mul sub 3 add 10 div}

\begin{document}
\psset{unit=1cm,linewidth=1.5pt}
\begin{pspicture}(-1,-1)(10,9)
  \psset{Beta=20,Alpha=160,subticks=7}
  \pstThreeDCoor[xMin=0,yMin=0,zMin=0,xMax=7,yMax=7,zMax=7,linewidth=1pt]
  \psset{linewidth=0.1pt,linecolor=gray}
  \pstThreeDPlaneGrid(0,0)(7,7)
  \pstThreeDPlaneGrid[planeGrid=xz,planeGridOffset=7](0,0)(7,7)
  \pstThreeDPlaneGrid[planeGrid=yz](0,0)(7,7)
  {\psset{linewidth=1.5pt}
   \pscustom[fillstyle=gradient,plotstyle=curve]{
    \psplotThreeD[xPlotpoints=200,yPlotpoints=1,drawStyle=xLines](0,7)(0,0){\func}
    \psplotThreeD[xPlotpoints=1,yPlotpoints=200,drawStyle=yLines](7,7)(0,7){\func}
    \psplotThreeD[xPlotpoints=200,yPlotpoints=1,drawStyle=xLines](7,0)(7,7){\func}
    \psplotThreeD[xPlotpoints=1,yPlotpoints=200,drawStyle=yLines](0,0)(7,0){\func}}}
  \pstThreeDPlaneGrid[planeGrid=yz,planeGridOffset=7](0,0)(7,7)
\end{pspicture}
\end{document}
