[pstricks] Strange 3D behaviour with viewpoint 1 -1 1

[Georg Verweyen]

The arrows of 3D graphics are broken if (and only if) all of the
following conditions are fullfilled:
- The linewidth is quite thick.
- The viewpoint is 1 -1 1.
- The ps file is transformed to pdf.
- The AdobeReader is /not/ set to "print as image".
- The file is printed, you will only see the effect on the paper,
while the display is okay.
You can see this behaviour when commenting and uncommenting the two
different lines with viewpoint settings in the following example.

Cheers, Georg

\documentclass{article}
\usepackage{%
            ,pst-all%
            ,pstricks-add%
            }
\defineTColor{hell}{black} % This provides transparency
                           % for the frame
\begin{document}
 \pagestyle{empty}
 \sffamily
\begin{pspicture}(12,12)
  \psset{%
    unit=0.75,%
    viewpoint=1.2 -1.5 1,% If this is active, everything's fine
%    viewpoint=1 -1 1,% try activating this line and print as pdf
    arrowinset=0,%
    arrowscale=0.75 0.2,%
    linecolor=lightgray,%
    linewidth=2%
  }
  \ThreeDput[normal=0 0 1](0,0,5){%Arrow to 2
    \psset{%
      arrows=-,%
    }
    \psline(0,1)(2,1)%
  }
  \ThreeDput[normal=1 0 0](2,1,5){%Frame at 2
    \psframe[linewidth=.2mm, style=hell](-2,-1)(2,1)
  }
  \ThreeDput[normal=1 0 0](2,1,5.5){%Label
    \Large \white Something
  }
  \ThreeDput[normal=0 0 1](0,0,5){%Arrow from 2
    \psset{%
      arrows=->,%
    }
    \psline(2,1)(5,1)%
  }
  \ThreeDput(2.2,1,5){%
    \makebox[0em][l]{\Large Arrow}
  }

\end{pspicture}
\end{document}