\def\grille{% quadrillage du plan Oxy
    \psPoint(-5,-5,0){S1}
    \psPoint(-5,5,0){S2}
    \psPoint(5,5,0){S3}
    \psPoint(5,-5,0){S4}
\pspolygon*[linecolor=gray!20](S1)(S2)(S3)(S4)
\multido{\ix=-5+1}{11}{%
    \psPoint(\ix\space,-5,0){A}
    \psPoint(\ix\space,5,0){B}
    \psline(A)(B)}
\multido{\iy=-5+1}{11}{%
    \psPoint(-5,\iy\space,0){A}
    \psPoint(5,\iy\space,0){B}
    \psline(A)(B)}
    \psPoint(0,0,0){O}
    \psPoint(5,0,0){X}
    \psPoint(0,5,0){Y}
    \psPoint(0,0,8){Z}
    \psline[arrowsize=0.3,arrowinset=0.2,linecolor=blue]{->}(O)(X)
    \psline[arrowsize=0.3,arrowinset=0.2,linecolor=blue]{->}(O)(Y)
    \psline[arrowsize=0.3,arrowinset=0.2,linecolor=blue]{->}(O)(Z)
    \uput[r](X){\textcolor{blue}{$x$}}\uput[u](Y){\textcolor{blue}{$y$}}%
    \uput[r](Z){\textcolor{blue}{$z$}}\uput[u](O){\textcolor{blue}{$O$}}}


\section{Fusing with \textit{jps code}}

We can also \Index{fuse solids} by passing the code directly using
\textit{jps code}. The calculation of the hidden parts is carried
out by the PostScript routines of the \texttt{solides.pro} file,
but the lines of code are ``encapsulated'' within a
\texttt{pspicture} environment thanks to the command
\verb+\codejps{ps code}+.

\subsection{Using \textit{jps code}}

\subsubsection{The choice of object}

\begin{compactitem}
  \item \texttt{[section] n newanneau}: choice of a cylindrical ring defined by
  the coordinates of the vertices of its intersection with the plane $Oyz$.
  \item \texttt{2  1.5  6 [4  16]  newcylindre}: choice of a vertical cylinder
with the following parameters:
  \begin{compactitem}
    \item \texttt{z0=2}: the position of the base centre on the axis $Oz$;
    \item \texttt{radius=1.5}: radius of the cylinder;
    \item \texttt{z1=6}: the position of the top centre on the
    axis $Oz$;
    \item \texttt{[4 16]}: the cylinder is sliced horizontally into 4 pieces and
vertically into 16 sectors.
  \end{compactitem}
  \end{compactitem}

\subsubsection{The transformations}

\begin{compactitem}
  \item \texttt{\{-1  2  5  translatepoint3d\} solidtransform}: the object
previously chosen is translated to the point with the
coordinates $(x=-1,y=2,z=5)$.
  \item \texttt{\{90  0  45  rotateOpoint3d\} solidtransform}: the object
previously chosen is rotated around the axes $(Ox,Oy,Oz)$, in
this order: rotation of 90$^\mathsf{o}$ about $(Ox)$ followed
by a rotation of 45$^\mathsf{o}$ about $(Oz)$.
\end{compactitem}

\subsubsection{The choice of object colour}

\begin{compactitem}
  \item dup (yellow) outputcolors: a yellow object illuminated in
  white light.
\end{compactitem}

\subsubsection{Fusing objects}

\begin{compactitem}
  \item The \Index{fusion} is finally made with the instruction \texttt{solidfuz}.
\end{compactitem}

\subsubsection{Designing objects}

\begin{compactitem}
  \item There are three drawing options:
  \begin{compactitem}
    \item \texttt{drawsolid}: only draw edges; hidden edges are drawn dashed;
    \item \texttt{drawsolid*}: draw and fill solids in their coded order (not
    a very interesting option at first glance); hidden edges are drawn dashed;
    \item \texttt{drawsolid**}: draw and fill solids with the
    painting algorithm; only those parts seen by the observer are
    drawn.
  \end{compactitem}
\end{compactitem}
\begin{center}
\psset{lightsrc=50 -50 50,viewpoint=40 16 32 rtp2xyz,Decran=40}
\psset{unit=0.4}
\begin{minipage}{0.3\linewidth}
\begin{pspicture}(-6,-5)(6,7)
\psframe*[linecolor=gray!40](-6,-5)(6,7)
\codejps{
% solide 1
 /tour {
    -6 1.5 6 [4 16] newcylindre
    dup (jaune) outputcolors
    } def
% solide 2
 /anneau {
    [4 -1 4 1 3 1 3 -1] 24 newanneau
   {0 0 -1 translatepoint3d} solidtransform
    dup (orange) outputcolors
    } def
% fusion
    tour anneau solidfuz
    drawsolid}
\end{pspicture}
\end{minipage}
\hfill
\begin{minipage}{0.3\linewidth}
\begin{pspicture}(-6,-5)(6,7)
\psframe*[linecolor=gray!40](-6,-5)(6,7)
\codejps{
% solide 1
 /tour {
    -6 1.5 6 [4 16] newcylindre
    dup (jaune) outputcolors
    } def
% solide 2
 /anneau {
    [4 -1 4 1 3 1 3 -1] 24 newanneau
   {0 0 -1 translatepoint3d} solidtransform
    dup (orange) outputcolors
    } def
% fusion
    tour anneau solidfuz
    drawsolid*}
\end{pspicture}
\end{minipage}
\hfill
\begin{minipage}{0.3\linewidth}
\begin{pspicture}(-6,-5)(6,7)
\psframe*[linecolor=gray!40](-6,-5)(6,7)
\codejps{
% solide 1
 /tour {
    -6 1.5 6 [4 16] newcylindre
    dup (jaune) outputcolors
    } def
% solide 2
 /anneau {
    [4 -1 4 1 3 1 3 -1] 24 newanneau
   {0 0 -1 translatepoint3d} solidtransform
    dup (orange) outputcolors
    } def
% fusion
    tour anneau solidfuz
    drawsolid**}
\psPoint(0,0,8){Z}
\psPoint(0,0,6){Z'}
\psline[arrowsize=0.3,arrowinset=0.2]{->}(Z')(Z)
\uput[u](Z){$z$}
\end{pspicture}
\end{minipage}
\end{center}

\begin{verbatim}
\psset{lightsrc=50 -50 50,viewpoint=50 20 50 rtp2xyz,Decran=50}
\begin{pspicture}(-6,-2)(6,8)
\psframe(-6,-2)(6,8)
\codejps{
% solide 1
    /tour{
      -6 1.5 6 [4 16] newcylindre
      dup (jaune) outputcolors
    } def
% solide 2
    /anneau{
      [4 -1 4 1 3 1 3 -1] 24 newanneau
      {0 0 -1 translatepoint3d} solidtransform
      dup (orange) outputcolors
    } def
% fusion
    tour anneau solidfuz
    drawsolid**}
\end{pspicture}
\end{verbatim}

\newpage

\subsection{A \Index{chloride ion}}
\begin{LTXexample}[width=6cm]
\begin{pspicture}(-3,-4)(3,4)
\psset{lightsrc=100 -50 -10,lightintensity=3,viewpoint=200 20 10 rtp2xyz,Decran=20}
{\psset{linewidth=0.5\pslinewidth}
\codejps{/Cl {9.02  [18 16] newsphere
{-90 0 0 rotateOpoint3d} solidtransform
 dup (Green) outputcolors} def
/Cl1 { Cl {10.25 10.25 10.25 translatepoint3d} solidtransform } def
/Cl2 { Cl {10.25 -10.25 10.25 translatepoint3d} solidtransform } def
/Cl3 { Cl {-10.25 -10.25 10.25 translatepoint3d} solidtransform } def
/Cl4 { Cl {-10.25 10.25 10.25 translatepoint3d} solidtransform } def
/Cl5 { Cl {10.25 10.25 -10.25 translatepoint3d} solidtransform } def
/Cl6 { Cl {10.25 -10.25 -10.25 translatepoint3d} solidtransform } def
/Cl7 { Cl {-10.25 -10.25 -10.25 translatepoint3d} solidtransform } def
/Cl8 { Cl {-10.25 10.25 -10.25 translatepoint3d} solidtransform } def
/Cs {8.38  [18 16] newsphere
 dup (White) outputcolors} def
/Cl12{ Cl1 Cl2 solidfuz} def
/Cl123{ Cl12 Cl3 solidfuz} def
/Cl1234{ Cl123 Cl4 solidfuz} def
/Cl12345{ Cl1234 Cl5 solidfuz} def
/Cl123456{ Cl12345 Cl6 solidfuz} def
/Cl1234567{ Cl123456 Cl7 solidfuz} def
/Cl12345678{ Cl1234567 Cl8 solidfuz} def
/C_Cs { Cl12345678 Cs solidfuz} def
C_Cs  drawsolid**}}%
\psPoint(0,0,0){P}
\psPoint(10.25,10.25,10.25){Cl1}
\psPoint(10.25,-10.25,10.25){Cl2}
\psPoint(-10.25,-10.25,10.25){Cl3}
\psPoint(-10.25,10.25,10.25){Cl4}
\psPoint(10.25,10.25,-10.25){Cl5}
\psPoint(10.25,-10.25,-10.25){Cl6}
\psPoint(-10.25,-10.25,-10.25){Cl7}
\psPoint(-10.25,10.25,-10.25){Cl8}
\pspolygon[linestyle=dashed](Cl1)(Cl2)(Cl3)(Cl4)
\pspolygon[linestyle=dashed](Cl5)(Cl6)(Cl7)(Cl8)
\psline[linestyle=dashed](Cl2)(Cl6)
\psline[linestyle=dashed](Cl3)(Cl7)
\psline[linestyle=dashed](Cl1)(Cl5)
\psline[linestyle=dashed](Cl4)(Cl8)
\pcline[offset=0.5]{<->}(Cl2)(Cl1)
\aput{:U}{a}
\pcline[offset=0.5]{<->}(Cl6)(Cl2)
\aput{:U}{a}
\end{pspicture}
\end{LTXexample}

We define the chloride ion $\mathrm{Cl^-}$:
\begin{verbatim}
/Cl {9.02  [12 8] newsphere
 {-90 0 0 rotateOpoint3d} solidtransform
 dup (Green) outputcolors} def
\end{verbatim}
which we shift to each vertex of a cube:
\begin{verbatim}
/Cl1 { Cl {10.25 10.25 10.25 translatepoint3d} solidtransform } def
/Cl2 { Cl {10.25 -10.25 10.25 translatepoint3d} solidtransform } def
/Cl3 { Cl {-10.25 -10.25 10.25 translatepoint3d} solidtransform } def
/Cl4 { Cl {-10.25 10.25 10.25 translatepoint3d} solidtransform } def
/Cl5 { Cl {10.25 10.25 -10.25 translatepoint3d} solidtransform } def
/Cl6 { Cl {10.25 -10.25 -10.25 translatepoint3d} solidtransform } def
/Cl7 { Cl {-10.25 -10.25 -10.25 translatepoint3d} solidtransform } def
/Cl8 { Cl {-10.25 10.25 -10.25 translatepoint3d} solidtransform } def
\end{verbatim}
Then a caesium ion $\mathrm{Cs^+}$ is placed in the center:
\begin{verbatim}
/Cs {8.38  [12 8] newsphere
 dup (White) outputcolors} def
\end{verbatim}
Finally we fuse the separate spheres in pairs.

\vfill


\subsection{A prototype of a \Index{vehicle}}
\begin{center}
\psset{lightsrc=100 0 100,viewpoint=25 10 10,Decran=30}
\begin{pspicture}(-6,-4)(6,8)
\pstVerb{/Pneu {
   /m {90 4 div} bind def
   /Scos {m cos 2 m mul cos add 3 m mul cos add} bind def
   /Z0 {h 4 div} bind def
   /c {Z0 Scos div} bind def
   /Z1 {Z0 c m cos mul add} bind def
   /Z2 {Z1 c m 2 mul cos mul add} bind def
   /R1 {R c m sin mul sub} bind def
   /R2 {R1 c m 2 mul sin mul sub} bind def
   /R3 {R2 c m 3 mul sin mul sub} bind def
   R h 4 div neg % 1
   R h 4 div % 2
   R1 Z1 % 3
   R2 Z2 % 4
   R3 h 2 div % 5
   r h 2 div  % 6
   r h 2 div neg  % 7
   R3 h 2 div neg % 8
   R2 Z2 neg % 9
   R1 Z1 neg % 10
   } def}%
\grille
\codejps{
/roue12 {
% solide 1
    /R 2 def /r 1 def /h 1 def
    [Pneu] 36 newanneau
     {90 0 90 rotateOpoint3d} solidtransform
     {3 4 2 translatepoint3d} solidtransform
     dup (White) outputcolors
% solide 2
    [Pneu] 36 newanneau
    {90 0 90 rotateOpoint3d} solidtransform
   {-3 4 2 translatepoint3d} solidtransform
    dup (White) outputcolors
% fusion
    solidfuz } def
/axe12{
0 0.1 6 [4 16] newcylindre
{90 0 90 rotateOpoint3d} solidtransform
{-3 4 2  translatepoint3d} solidtransform
dup (White) outputcolors
} def
/roue12axes {
roue12 axe12 solidfuz } def
/roue34 {
% solide 3
   /R 1.5 def /r 1 def /h 1 def
    [Pneu] 36 newanneau
    {90 0 110 rotateOpoint3d} solidtransform
   {3 -4 1.5 translatepoint3d} solidtransform
    dup (White) outputcolors
% solide 4
    [Pneu] 36 newanneau
   {90 0 110 rotateOpoint3d} solidtransform
   {-3 -4 1.5 translatepoint3d} solidtransform
    dup (White) outputcolors
% fusion
    solidfuz } def
/axe34{
0 0.1 6  [16 16] newcylindre
{90 0 90 rotateOpoint3d} solidtransform
{-3 -4 1.5  translatepoint3d} solidtransform
dup (White) outputcolors
} def
/roue34axes34 {
roue34 axe34 solidfuz } def
/roues {roue34axes34 roue12axes solidfuz} def
/chassis {
0 1 8  [4 16] newcylindre
{100 0 0 rotateOpoint3d} solidtransform
{0 4 2.5  translatepoint3d} solidtransform
dup (White) outputcolors
} def
roues chassis solidfuz
    drawsolid**}
\psPoint(0,0,2.7){Z'}
\psline[arrowsize=0.3,arrowinset=0.2,linecolor=blue]{->}(Z')(Z)
\end{pspicture}
\end{center}
We have to operate in several steps to fuse the solids in pairs:
\begin{compactitem}
  \item We first fuse the two front wheels \texttt{roue12}:
  \begin{verbatim}
/roue12 {
% solide 1
    /R 2 def /r 1 def /h 1 def
    [Pneu] 36 newanneau
     {90 0 90 rotateOpoint3d} solidtransform
     {3 4 2 translatepoint3d} solidtransform
     dup (White) outputcolors
% solide 2
    [Pneu] 36 newanneau
    {90 0 90 rotateOpoint3d} solidtransform
   {-3 4 2 translatepoint3d} solidtransform
    dup (White) outputcolors
% fusion
    solidfuz } def
  \end{verbatim}
  \item Then the two wheels and their axis:
  \begin{verbatim}
/axe12{
0 0.1 6  [4 16] newcylindre
{90 0 90 rotateOpoint3d} solidtransform
{-3 4 2  translatepoint3d} solidtransform
dup (White) outputcolors
} def
/roue12axes {
roue12 axe12 solidfuz } def
\end{verbatim}
  \item After that the rear wheels and their axis:
  \begin{verbatim}
/roue34 {
% solide 3
   /R 1.5 def /r 1 def /h 1 def
    [Pneu] 36 newanneau
    {90 0 110 rotateOpoint3d} solidtransform
   {3 -4 1.5 translatepoint3d} solidtransform
    dup (White) outputcolors
% solide 4
    [Pneu] 36 newanneau
   {90 0 110 rotateOpoint3d} solidtransform
   {-3 -4 1.5 translatepoint3d} solidtransform
    dup (White) outputcolors
% fusion
    solidfuz } def
/axe34{
0 0.1 6 [16 16] newcylindre
{90 0 90 rotateOpoint3d} solidtransform
{-3 -4 1.5  translatepoint3d} solidtransform
dup (White) outputcolors
} def
/roue34axes34 {
roue34 axe34 solidfuz } def
\end{verbatim}

\item Then fuse the two wheel assemblies:
\begin{verbatim}
/roues {roue34axes34 roue12axes solidfuz} def
\end{verbatim}

\item The final step is to fuse the previously generated solid with
the chassis:
\begin{verbatim}
/chassis {
0 1 8  [4 16] newcylindre
{100 0 0 rotateOpoint3d} solidtransform
{0 4 2.5  translatepoint3d} solidtransform
dup (White) outputcolors
} def
roues chassis solidfuz
    drawsolid**}
\end{verbatim}
\end{compactitem}


\subsection{A \Index{wheel} -- or a space station}

\begin{center}
\begin{pspicture}(-6,-5)(6,6)
\psset{lightsrc=50 -50 50,viewpoint=40 50 60,Decran=60,linewidth=0.5\pslinewidth}
%\psframe*[linecolor=black](-6,-5)(6,5)
\codejps{
 /rayon0 {
     1 0.2 6 [4 16] newcylindre
     {90 0 0 rotateOpoint3d} solidtransform
      dup (White) outputcolors
   } def
36 36 360 {
    /angle exch def
  /rayon1 {
     1 0.2 6  [4 16] newcylindre
     {90 0 angle rotateOpoint3d} solidtransform
      dup (White) outputcolors
   } def
  /rayons {rayon0 rayon1 solidfuz} def
  /rayon0 rayons def
  } for
 /moyeu { -2 1 2  [4 10] newcylindre dup (jaune) outputcolors} def
 /rayonsmoyeu {rayons  moyeu solidfuz} def
 /pneu {2 7 [18 36] newtore dup (White) outputcolors} def
 /ROUE {pneu rayonsmoyeu solidfuz} def
  ROUE  drawsolid**}
\end{pspicture}
\end{center}
We define the first spoke:
\begin{verbatim}
 /rayon0 {
     1 0.2 6 [4 16] newcylindre
     {90 0 0 rotateOpoint3d} solidtransform
      dup (White) outputcolors
   } def
\end{verbatim}
Then, with a loop, we fuse all the spokes of the wheel:
\begin{verbatim}
36 36 360 {
    /angle exch def
  /rayon1 {
     1 0.2 6  [4 16] newcylindre
     {90 0 angle rotateOpoint3d} solidtransform
      dup (White) outputcolors
   } def
  /rayons {rayon0 rayon1 solidfuz} def
  /rayon0 rayons def
  } for
\end{verbatim}
After that, we draw the hub and the tyre of the wheel, and finally
fuse all of them:
\begin{verbatim}
 /moyeu { -0.5 1 0.5  [4 10] newcylindre dup (White) outputcolors} def
 /rayonsmoyeu {rayons  moyeu solidfuz} def
 /pneu {2 7 [18 36] newtore dup (jaune) outputcolors} def
 /ROUE {pneu rayonsmoyeu solidfuz} def
  ROUE  drawsolid**
\end{verbatim}


\subsection{Intersection of two cylinders}

\begin{LTXexample}[width=8cm]
\begin{pspicture}(-4,-3)(6,3)
\psset{lightsrc=50 -50 50,viewpoint=100 -30
40,Decran=100,linewidth=0.5\pslinewidth, unit=0.5}
\codejps{
 /cylindre1 {
     -6 2 6 [36 36] newcylindrecreux %newcylindre
     {90 0 0 rotateOpoint3d} solidtransform
      dup (Yellow) (White) inoutputcolors
   } def
 /cylindre2 {
     -6 2 6 [36 36] newcylindrecreux %newcylindre
     {90 0 90 rotateOpoint3d} solidtransform
      dup (Yellow) (White) inoutputcolors
   } def
 /UnionCylindres {cylindre1 cylindre2 solidfuz} def
  UnionCylindres  drawsolid**}
\end{pspicture}
\end{LTXexample}


\subsection{Intersection between a sphere and a cylinder}

This time we draw the curve of intersection using
\verb+\psSolid[object=courbe]+.

\begin{LTXexample}[width=8cm]
\psset{unit=0.5,lightsrc=50 -50 50,viewpoint=100 0 0 rtp2xyz,Decran=110,linewidth=0.5\pslinewidth}
\begin{pspicture}(-7,-6)(5,6)
\defFunction{F}(t){t cos dup mul 5 mul}{t cos t sin mul 5 mul}{t sin 5 mul}
\codejps{%
   /cylindre1 {
       -5 2.5 5 [36 36] newcylindre
       {2.5 0 0 translatepoint3d} solidtransform
        dup (White) outputcolors
   } def
   /sphere1 {
        5 [36 72] newsphere
        dup (White) outputcolors
   } def
   /CS {cylindre1 sphere1 solidfuz} def
   CS drawsolid**}
\psPoint(0,0,0){O}
\psSolid[object=courbe,r=0,
   function=F,
   range=0 360,
   linecolor=red,linewidth=4\pslinewidth]
\end{pspicture}
\end{LTXexample}


\subsection{Two linked \Index{rings}}

\begin{LTXexample}[width=8cm]
\begin{pspicture}(-5,-4)(3,3)
\psset{lightsrc=50 50 50,viewpoint=40 50 60,Decran=30,unit=0.85}
\codejps{
 /anneau1 {1 7 [12 36] newtore
 {0 0 0 translatepoint3d} solidtransform
 dup (Yellow) outputcolors} def
 /anneau2 {1 7 [12 36] newtore
 {90 0 0 rotateOpoint3d} solidtransform
 {7 0 0 translatepoint3d} solidtransform
 dup (White) outputcolors} def
 /collier {anneau1 anneau2 solidfuz} def
  collier  drawsolid**}
\end{pspicture}
\end{LTXexample}



\subsection{The \Index{methane molecule}: wooden model}

\begin{LTXexample}[width=8cm]
\begin{pspicture}(-4.5,-4)(3.2,5)
\psset{lightsrc=50 50 10,lightintensity=2,viewpoint=100 50 20 rtp2xyz,
Decran=30}
\psset{linecolor={[cmyk]{0,0.72,1,0.45}},linewidth=0.5\pslinewidth,
  unit=1}
%\psframe[fillstyle=solid,fillcolor=green!20](-4,-4)(3.2,5)
\pstVerb{/hetre {0.764 0.6 0.204 setrgbcolor} def
         /chene {0.568 0.427 0.086 setrgbcolor} def
         /bois {0.956 0.921 0.65 setrgbcolor} def
         }%
\codejps{
 /H1 {
 2  [18 16] newsphere
 {-90 0 0 rotateOpoint3d} solidtransform
 {0 10.93 0 translatepoint3d} solidtransform
 dup (hetre) outputcolors} def
  /L1 {
     0 0.25 10  [12 10] newcylindre
     {-90 0 0 rotateOpoint3d} solidtransform
      dup (bois) outputcolors
   } def
/HL1{ H1 L1  solidfuz} def
/HL2 { HL1 {0 0 -109.5 rotateOpoint3d} solidtransform } def
/HL3 { HL2 {0 -120 0 rotateOpoint3d} solidtransform } def
/HL4 { HL2 {0 120 0 rotateOpoint3d} solidtransform } def
 /C {3  [18 16] newsphere
  {90 0 0 rotateOpoint3d} solidtransform
   dup (chene) outputcolors} def
/HL12 { HL1 HL2 solidfuz} def
/HL123 { HL12 HL3 solidfuz} def
/HL1234 { HL123 HL4 solidfuz} def
/methane { HL1234 C solidfuz} def
  methane  drawsolid**}
\end{pspicture}
\end{LTXexample}


\subsection{The \Index{thiosulphate ion}}

\begin{center}
\begin{pspicture}(-4,-3)(4.5,5.5)
\psset{lightsrc=100 10 -20,lightintensity=3,viewpoint=200 30
20 rtp2xyz,Decran=40}
%\psframe(-4,-3)(4.5,5.5)
{\psset{linewidth=0.5\pslinewidth}
\codejps{
/Soufre1 {3.56  [20 16] newsphere
 dup (Yellow) outputcolors} def
/Soufre2 {3.56  [20 16] newsphere
 {0 0.000 20.10 translatepoint3d} solidtransform
 dup (Yellow) outputcolors} def
% Liaison simple
/LiaisonR {
     7.5 0.5 15  [10 10] newcylindre
      dup (Red) outputcolors
   } def
/LiaisonY {
     0 0.5 7.5  [10 10] newcylindre
      dup (Yellow) outputcolors
   } def
% fin Liaison simple
/Liaison{LiaisonR LiaisonY solidfuz} def
/Ox {2.17  [20 16] newsphere
     {0 0 15 translatepoint3d} solidtransform
     dup (Red) outputcolors} def
/LO { Liaison Ox solidfuz} def
/LO1 { LO  {0 -109.5 0 rotateOpoint3d} solidtransform } def
/LOx1 { LO1  {0 0 120 rotateOpoint3d} solidtransform } def
% fin liaison simple S-O
% Liaison double S=O
/LiaisonD1 {Liaison {-0.75 0 0 translatepoint3d} solidtransform} def
/LiaisonD2 {Liaison {0.75 0 0 translatepoint3d} solidtransform} def
/LiaisonDD { LiaisonD1 LiaisonD2 solidfuz} def
/LiaisonDOx {LiaisonDD Ox solidfuz} def
/LiaisonDOx1 {LiaisonDOx {0 -109.5 0 rotateOpoint3d} solidtransform } def
/LiaisonDOx2 {LiaisonDOx1 {0  0 -120 rotateOpoint3d} solidtransform } def
/LO12 { LiaisonDOx1 LiaisonDOx2 solidfuz} def
/LO123 {LO12 LOx1 solidfuz} def
% liaison simple S-S
/L4 { 0 0.5 20.10  [16 10] newcylindre
      dup (Yellow) outputcolors
    } def
/S1L4{ Soufre1 L4 solidfuz} def
/S1S2L4{ S1L4 Soufre2 solidfuz} def
/S2O3 { S1S2L4 LO123 solidfuz} def
S2O3  drawsolid**}
\axesIIID(0,0,0)(25,20,25)}
\psPoint(0,0,20.1){S2}
\psPoint(-14.14,0,-5){O1}
\psPoint(7.07,-12.24,-5 ){O2}
\psPoint(7.07,12.24,-5 ){O3}
\pcline[linestyle=dotted]{<->}(O2)(O)
\aput{:U}{15 pm}
\pcline[linestyle=dotted]{<->}(O)(S2)
\aput{:U}{\small 20,1 pm}
\pcline[linestyle=dotted]{<->}(O2)(O3)
\lput*{:U}{\small 24,5 pm}
\pcline[linestyle=dotted]{<->}(O2)(S2)
\lput*{:U}{\small 28,8 pm}
\pstMarkAngle[arrows=<->,MarkAngleRadius=0.8,linestyle=dotted]{O2}{O}{O3}{\footnotesize 109,4$^{\mathrm{o}}$}
\pstMarkAngle[arrows=<->,MarkAngleRadius=0.8,linestyle=dotted]{O1}{O}{S2}{\footnotesize 109,5$^{\mathrm{o}}$}
\rput(0,-2.5){$\mathrm{S_2^{\phantom{2}}O_3^{2-}}$}
\end{pspicture}
\end{center}

We first define the two sulphur atoms and place them on the $Oz$
axis. $\mathrm{S_1}$ is placed at the origin $O$.
\begin{verbatim}
\codejps{
/Soufre1 {3.56  [20 16] newsphere
 dup (Yellow) outputcolors} def
/Soufre2 {3.56  [20 16] newsphere
 {0 0.000 20.10 translatepoint3d} solidtransform
 dup (Yellow) outputcolors} def
\end{verbatim}
Then the single bond \textsf{S-O} using the following convention:
half red---the half connected to \textsf{O}, and half yellow---the half connected to \textsf{S}.
\begin{verbatim}
/LiaisonR {
     7.5 0.5 15  [10 10] newcylindre
      dup (Red) outputcolors
   } def
/LiaisonY {
     0 0.5 7.5  [10 10] newcylindre
      dup (Yellow) outputcolors
   } def
/Liaison{LiaisonR LiaisonY solidfuz} def
\end{verbatim}
The oxygen atom, its bond, and the setting of the combined unit:
\begin{verbatim}
/Ox {2.17  [20 16] newsphere
     {0 0 15 translatepoint3d} solidtransform
     dup (Red) outputcolors} def
/LO { Liaison Ox solidfuz} def
/LO1 { LO  {0 -109.5 0 rotateOpoint3d} solidtransform } def
/LOx1 { LO1  {0 0 120 rotateOpoint3d} solidtransform } def
% fin liaison simple S-O
\end{verbatim}
For the double bond \textsf{S=O}, we take the single bond above
and duplicate it with shifts of 0.75~cm along the $Ox$ axis.
\begin{verbatim}
% Liaison double S=O
/LiaisonD1 {Liaison {-0.75 0 0 translatepoint3d} solidtransform} def
/LiaisonD2 {Liaison {0.75 0 0 translatepoint3d} solidtransform} def
/LiaisonDD { LiaisonD1 LiaisonD2 solidfuz} def
\end{verbatim}
Connecting it to the \textsf{O} atom:
\begin{verbatim}
/LiaisonDOx {LiaisonDD Ox solidfuz} def
\end{verbatim}
and with two successive rotations we position the two bonds
\textsf{=O}:
\begin{verbatim}
/LiaisonDOx1 {LiaisonDOx {0 -109.5 0 rotateOpoint3d} solidtransform } def
/LiaisonDOx2 {LiaisonDOx1 {0  0 -120 rotateOpoint3d} solidtransform } def
\end{verbatim}
The following step consists of fusing the two connections:
\begin{verbatim}
/LO12 { LiaisonDOx1 LiaisonDOx2 solidfuz} def
/LO123 {LO12 LOx1 solidfuz} def
\end{verbatim}
Then the single bond \textsf{S-S} is created:
\begin{verbatim}
% liaison simple S-S
/L4 { 0 0.5 20.10  [16 10] newcylindre
      dup (Yellow) outputcolors
    } def
\end{verbatim}
and fused with the two atoms \textsf{S-S}:
\begin{verbatim}
/S1L4{ Soufre1 L4 solidfuz} def
/S1S2L4{ S1L4 Soufre2 solidfuz} def
\end{verbatim}
The last step will be to fuse the two \textsf{S-S} and the three
\textsf{O} already equipped with their bonds:
\begin{verbatim}
/S2O3 { S1S2L4 LO123 solidfuz} def
S2O3  drawsolid**}
\end{verbatim}

\endinput