[pstricks] 3D Clipping

[Herbert Voss]

geotal wrote:

> Thanks.  pst-vue3d is excellent.  

indeed

 > Now instead of a sphere,
> I would like to plot the circular paraboloid f(x,y) = x^2 + y^2,  
> clipped (bounded) by the plane z = 1, which resembles a bowl, close to a 
> semi-sphere.
> 
> I have looked at the code of the sphere and semi-sphere in pst-vue3d to 
> see if I could define the paraboloid but it is
> beyond me.

a parametrical plot with a limited z value is easy

x(t,u) = a sqrt(u/h) cos t
y(t,u) = a sqrt(u/h) sin t
z(t,u) = u

u=[0;1], t=[0;360)  a is the radius at the height h


\documentclass[12pt]{article}
\usepackage{pst-3dplot}
\begin{document}

\psset{xunit=5cm,yunit=5cm}
\begin{pspicture}(-1,-1)(1,1)
\pstThreeDCoor[xMax=1,yMax=1,zMin=0.1,zMax=2]
\pstVerb{
   /height 1 def
   /radius 1 def
}
\parametricplotThreeD[yPlotpoints=50,plotstyle=curve](0,360)(0,1){%
         radius u height div sqrt mul t cos mul
         radius u height div sqrt mul t sin mul
         u  }
\end{pspicture}

\end{document}


Herbert