[pstricks] Slices of a solid of revolution

[Herbert Voss]

Hamed wrote:
> Hi everybody,
>
> First of all, thanks a lot for Juergen,
>
> Second, my question was about the slice of a solid of revolution. 
>
> I meant can we do the slice for the solid obtained by rotating the region
> bounded by y=x and y=x^2 about the x-axis
>   
hope, this helps

Herbert

\documentclass{article}
\usepackage{pst-plot}
\SpecialCoor
\usepackage{multido}
\parindent=0pt

#1: x1; #2: x2: #3: no of steps; #4: equation
\def\psVolume(#1,#2)#3#4{{%  
  \psplot{#1}{#2}{#4}\psplot{#1}{#2}{#4 neg}
  \multido{\iA=1+1}{#3}{%
    \pscustom[fillcolor=green,fillstyle=solid]{%
      \code{
        /dX #2 #1 sub #3 div def
        /Start dX \iA\space 1 sub mul #1 add def
        /End Start dX add def
        /Height End Start add 2 div /x ED #4 def }
      \psellipticarc(!Start 0)(! Height 8 div Height){90}{270}
      \rlineto(! dX 0)
      \psellipticarc(!End 0)(! Height 8 div Height){270}{90}
      \rlineto(!dX neg 0)}}
  \psellipticarc(#2,0)(! #2 dup #1 sub #3 div 2 div sub
    /x ED x 4 div #4){90}{270}
 
\psset{plotstyle=line,linestyle=dashed,plotpoints=40,dotstyle=*,dotsize=0.5pt}
  \psplot{#1}{#2}{#4}\psplot{#1}{#2}{#4 neg}%
}\ignorespaces}

\begin{document}

\psset{xunit=2}
\begin{pspicture}(-0.5,-4)(4,4)
  \psaxes{->}(0,0)(0,-4)(3,4)
  \psVolume(0,1){2}{x}
  \psVolume(1,2){2}{x dup mul}
  \psline(2,0)(3,0)
\end{pspicture}

\begin{pspicture}(-0.5,-4)(4,4)
  \psaxes{->}(0,0)(0,-4)(3,4)
  \psVolume(0,1){20}{x}
  \psVolume(1,2){20}{x dup mul}
  \psline(2,0)(3,0)
\end{pspicture}

\end{document}