\section{The option \texttt{transform}}

The option \Lkeyword{transform}, which is nothing else than a formula $\mathbb{R}^3 \rightarrow  \mathbb{R}^3$,
which is applied to every point of the solid. In the first example, the object that accepts the transformation is a cube.
The referenced cube is yellow, the transformed cube is green and the cube before the \Index{transformation} is setup with a reticule.

\subsection{Identical scaling factor in the three coordinates}

The scaling factor is set to $0.5$. It is either introduced within the PostScript variable `\texttt{/Facteur}':
\begin{verbatim}
\pstVerb{/Facteur {.5 mulv3d} def}%
\end{verbatim}
and then passed to the option \verb+transform+:
\begin{verbatim}
\psSolid[object=cube,a=2,ngrid=3,
         transform=Facteur](2,0,1)%
\end{verbatim}
or directly passed to the option:
\begin{verbatim}
\psSolid[object=cube,a=2,ngrid=3,
         transform={.5 mulv3d}](2,0,1)%
\end{verbatim}
Here the \textit{jps} abbreviation \texttt{transform=\{.5 mulv3d\}} for a function $\mathbb{R}^3 \rightarrow \mathbb{R}^3$ was used.

Another method would be to use the code
\begin{verbatim}
\defFunction[algebraic]{matransformation}(x,y,z)
   {.5*x}
   {.5*y}
   {.5*z}
\end{verbatim}
and then pass it to the option
\texttt{transform=matransformation}.
\begin{LTXexample}[pos=t]
\psset{viewpoint=20 60 20 rtp2xyz,lightsrc=viewpoint,Decran=20}
\begin{pspicture}(-5,-3)(6,5)
\psSolid[object=grille,base=-4 4 -4 4,fillcolor=red!50]%
\axesIIID(0,0,0)(4,4,4)%
\psSolid[object=cube,fillcolor=yellow!50,
      a=2,ngrid=3](-2,0,1)
\psSolid[object=cube,fillcolor=green!50,
      a=2,transform={.5 mulv3d},
      ngrid=3](2,0,1)
\psSolid[object=cube,
      action=draw,
      a=2,ngrid=3](2,0,1)
\end{pspicture}
\end{LTXexample}

\encadre{The scaling factor also affects the position coordinates of the cube's center.}

\subsection{Different scaling factors for the three coordinates}

Let's for example use a factor 0.75 for $x$, 4
for $y$ and 0.5 for $z$ using the function \texttt{scaleOpoint3d} from the
 \textit{jps} library---so a cube will be transformed to a cuboid.
\begin{LTXexample}[pos=t]
\psset{viewpoint=20 60 20 rtp2xyz,lightsrc=viewpoint,Decran=20}
\begin{pspicture}(-5,-3)(6,5)
\psSolid[object=grille,base=-4 4 -4 4,fillcolor=red!50]%
\axesIIID(0,0,0)(4,4,4)%
\psSolid[object=cube,fillcolor=yellow!50,
      a=2,ngrid=3](-2,0,1)
\psSolid[object=cube,fillcolor=green!50,
      a=2,transform={.75 4 .5 scaleOpoint3d},
      ngrid=3](2,0,1)
\psSolid[object=cube,
      action=draw,
      a=2,ngrid=3](2,0,1)
\end{pspicture}
\end{LTXexample}

\subsection{Transformation associated with the distance to the origin}

Here an example applied to a cube:

\begin{equation*}
\left\lbrace\begin{aligned}
x'&=\big(0.5\sqrt{x^2+y^2+z^2}+1-0.5\sqrt{3}\big)x \\
y'&=\big(0.5\sqrt{x^2+y^2+z^2}+1-0.5\sqrt{3}\big)y \\
z'&=\big(0.5\sqrt{x^2+y^2+z^2}+1-0.5\sqrt{3}\big)z
\end{aligned}\right.
\end{equation*}

\begin{LTXexample}[width=7cm]
\begin{pspicture}(-3,-4)(4,3)
\psset{viewpoint=20 60 20 rtp2xyz,lightsrc=10 15 7,Decran=20}
\pstVerb{
/gro {
4 dict begin
   /M defpoint3d
   /a .5 def
   /b 1 a 3 sqrt mul sub def
   /k M norme3d a mul b add def
   M k mulv3d
end
} def}%
\psset{linewidth=.02,linecolor=gray}
\psSolid[object=cube,a=3,ngrid=9,
      transform=gro]%
\end{pspicture}
\end{LTXexample}
%\newpage

\subsection{Bending and \Index{torsion} of beams}

The solid to the left is a prism of the height 10 cm with 20 floors
(\texttt{\Lkeyword{ngrid}=20 2}). In every floor, an additional angle of rotation---for example 10$^{\mathrm{o}}$ around the $Oz$ axis is---given.
 Now that the adjacent floors have a distance of $0.5$~cm, one multiplies $z\times20$.

La flexion est envisag\'{e}e dans le plan $xOz$ sous l'action d'une force perpendiculaire \`{a} la poutre appliqu\'{e}e en son extr\'{e}mit\'{e}.

\begin{LTXexample}[pos=t]
\psset{viewpoint=100 50 20 rtp2xyz,lightsrc=viewpoint,Decran=100,unit=0.65}
\begin{pspicture}(-3,-1)(3.5,11)
\psSolid[object=grille,base=-2 2 -2 2,ngrid=8]%
\psSolid[object=prisme,h=10,ngrid=20 2,
        base=0.5 0 0.5 0.5 0 0.5 -0.5 0.5 -0.5 0 -0.5 -0.5 0 -0.5 0.5 -0.5]%
\end{pspicture}
\begin{pspicture}(-3,-1)(3.5,11)
\psSolid[object=grille,base=-2 2 -2 2,ngrid=8]%
\pstVerb{
/torsion {% on tourne de 10 degr\'{e}s suivant l'axe Oz \`{a} chaque niveau
2 dict begin
   /M defpoint3d % on r\'{e}cup\`{e}re les coordonn\'{e}es
   M /z exch def pop pop
    M 0 0 z 20 mul rotateOpoint3d
end} def}%
\psSolid[object=prisme,h=10,ngrid=20 2,
        base=0.5 0 0.5 0.5 0 0.5 -0.5 0.5 -0.5 0 -0.5 -0.5 0 -0.5 0.5 -0.5,
        transform=torsion]%
\psTransformPoint[RotZ=20](2 0 10)(0,0,0){A}
\psTransformPoint[RotZ=20](2 1 10)(0,0,0){A'}
\psTransformPoint[RotZ=20](-2 0 10)(0,0,0){B}
\psTransformPoint[RotZ=20](-2 -1 10)(0,0,0){B'}
\psline[linecolor=red]{v-v}(A')(A)(B)(B')
\end{pspicture}
\begin{pspicture}(-3.5,-1)(3,11)
\psSolid[object=grille,base=-2 2 -2 2,ngrid=8]%
\pstVerb{%  id\'{e}e de Christophe Poulain
/flexion {% on tourne de 2 degr\'{e}s suivant l'axe Oy \`{a} chaque niveau
2 dict begin
   /M defpoint3d % on r\'{e}cup\`{e}re les coordonn\'{e}es
   M /z exch def pop pop
    M 0 z 2 mul 0 rotateOpoint3d
end} def}%
\axesIIID(0,0,0)(3,3,10)
\psSolid[object=prisme,h=10,ngrid=20 2,
        base=0.5 0 0.5 0.5 0 0.5 -0.5 0.5 -0.5 0 -0.5 -0.5 0 -0.5 0.5 -0.5,
        transform=flexion]%
\psTransformPoint[RotY=20](0.5 0 10)(0,0,0){A}
\psPoint(3 20 cos mul 20 sin 10 mul add 0.5 add,0, 20 cos 10 mul 20 sin 3 mul sub){A'}
\psdot(A)\psline[linecolor=red]{-v}(A)(A')
\end{pspicture}
\end{LTXexample}

\endinput