[pstricks] ngrid has maximum under calottesphere

[Werner Grundlingh]

Consider the following minimal example:

\documentclass{article}

\usepackage{pst-solides3d}

\begin{document}

\begin{pspicture}(-5,-5)(5,5)
\psset{
    viewpoint=0 20 4,
    Decran=25,
    lightsrc=viewpoint,
    lightintensity=1,
}

  \psSolid[
    object=calottesphere,
    r=3,
    ngrid=90 120,% <---------------- change this to ngrid=150 150
    theta=30,phi=-90,
    grid,hollow,
    fillcolor=white,incolor=green,
    action=draw**
  ](0,0,0)

\end{pspicture}

\end{document}

The result looks like this:

[image: Inline image 1]

However, changing the ngrid parameters to (say) ngrid=150 150, the output
looks like this:

[image: Inline image 2]

Why is that? I'd like to get a "bowl" that is really smooth, and therefore
would like to increase the ngrid parameters to something large without
causing the above problem.
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