Update user guide entry for interpptstopts

docs/user-guide/utilities/fieldconvert.tex

@@ -168,8 +168,8 @@ possibly also Reynolds stresses) into single file;
 \item \inltt{innerproduct}: take the inner product between one or a series of fields with another field (or series of fields).
 \item \inltt{interpfield}: Interpolates one field to another, requires fromxml, fromfld to be defined;
 \item \inltt{interppointdatatofld}: Interpolates given discrete data using a finite difference approximation to a fld file given an xml file;
-\item \inltt{interppoints}: Interpolates a field to a set of points. Requires fromfld, fromxml to be defined, and a topts, line, plane or block of target points;
-\item \inltt{interpptstopts}: Interpolates a set of points to another, requires fromfld and fromxml to be defined, a line or plane of points can be defined;
+\item \inltt{interppoints}: Interpolates a field to a set of points. Requires fromfld, fromxml to be defined, and a topts, line, plane or box of target points;
+\item \inltt{interpptstopts}: Interpolates a set of points to another. Requires a topts, line, plane or box of target points;
 \item \inltt{isocontour}: Extract an isocontour of ``fieldid'' variable and at value ``fieldvalue''. Optionally ``fieldstr'' can be specified for a string definition or ``smooth'' for smoothing;
 \item \inltt{jacobianenergy}: Shows high frequency energy of Jacobian;
 \item \inltt{qualitymetric}: Evaluate a quality metric of the underlying mesh to show mesh quality;
@@ -641,7 +641,34 @@ This module  runs in parallel for the line, plane and box extraction of points.
 \subsection{Interpolate a set of points to another: \textit{interpptstopts} module}
 You can interpolate one set of points to another using the following command:
 \begin{lstlisting}[style=BashInputStyle]
-FieldConvert -m interpptstopts:...
+FieldConvert file1.pts -m interpptstopts:topts=file2.pts file2.dat
+\end{lstlisting}
+This command will interpolate the data in  \inltt{file1.pts} to a new set
+of points defined in \inltt{file2.pts} and output it to
+\inltt{file2.dat}.
+
+Similarly to the \textit{interppoints} module, the target point distribution
+can also be specified using the \inltt{line}, \inltt{plane} or \inltt{box}
+options. The optional arguments \inltt{clamptolowervalue},
+\inltt{clamptouppervalue}, \inltt{defaultvalue} and \inltt{cp} are also
+supported with the same meaning as in \textit{interppoints}.
+
+One useful application for this module is with 3DH1D expansions, for which
+currently the \textit{interppoints} module does not work. In this case, we can
+use for example
+\begin{lstlisting}[style=BashInputStyle]
+FieldConvert file1.xml file1.fld -m interpptstopts:\
+    plane=npts1,npts2,x0,y0,z0,x1,y1,z1,x2,y2,z2,x3,y3,z3 \
+    file2.dat
+\end{lstlisting}
+With this usage, the \textit{equispacedoutput} module will be automatically
+called to interpolate the field to a set of equispaced points in each element.
+The result is then interpolated to a plane by the \textit{interpptstopts} module.
+
+\begin{notebox}
+	This module  does not work in parallel.
+\end{notebox}
+
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