* much easier.
*
*
- * \subsection{GNUPLOT format}
+ * \subsection{GNUPLOT draft format}
*
* The GNUPLOT format is not able to handle data on unstructured grids
* directly. Directly would mean that you only give the vertices and
* duplicates the functionality of the #Triangulation<dim>::print_gnuplot()#
* functions. These, however, offer more functionality in some respect.
* The grid is represented as a sequence of lines, where each cell is
- * a sequence of five vertices (the first one is appended to close the
- * contour of the cell) with the data appended after each vertex. Each cell
+ * a sequence of five vertices (the first one is appended at the end to close
+ * the contour of the cell) with the data appended after each vertex. Each cell
* is therefore a sequence of five lines #x y v1 v2 ...# forming together
* the bounding line of this cell. After each cell, two newlines are inserted
* to prevent GNUPLOT from joining the lines bounding two cells.
* plot of the (#x-2#)th data set. For example, using #x=4# would mean to
* plot the second data set.
*
+ * This format is somewhat restricted to coninuous data and to finite elements
+ * of first order only. The reason for the first restriction is that it takes
+ * nodal values and can therefore only work if a finite element has degrees of
+ * freedom in the vertices of each cell. This is not the case for discontinuous
+ * elements. The second restriction is only a problem of quality of output: you
+ * actually can print quadratic or higher order elements using this style, but
+ * you will only seem the contour of each cell with the bounding lines of each
+ * cell being straight lines. You won't see the structure of the solution in the
+ * interior of a cell nor on the lines bounding it.
+ *
+ *
+ * \subsection{GNUPLOT 'quality' format}
+ *
+ * To remedy the abovementioned problems, the GNUPLOT 'quality' format was
+ * introduced. As noted above, GNUPLOT can handle tensor grids and displays
+ * them quite nicely, including hidden line removal. It can also handle more
+ * than one tensor grid, then called a patch. The idea now is to describe
+ * each cell as a patch of $N\times N$ points (in 2D). For linear elements,
+ * $2\times 2$ is sufficient, but for higher elements you will want to use
+ * a higher number. The #write_gnuplot# function writes the data in this format
+ * and the argument it takes is the number of subintervals it divides each cell
+ * into, i.e. $N-1$.
+ *
+ * This output routine also addresses the problem introduced with discontinuous
+ * elements, since it takes its data locally from each cell and displays it
+ * as a patch separately; it therefore does not use continuity and GNUPLOT will
+ * also plot discontinuities, if they are there.
+ *
*
* \subsection{POVRAY format}
*
* term of memory and speed to the triangle mesh supported by POVRAY.
*
*
- * @author Wolfgang Bangerth, 1998
+ * @author Wolfgang Bangerth, 1998; GNUPLOT 'quality' format by Guido Kanschat with documentation by Wolfgang Bangerth, 1998
*/
template <int dim>
class DataOut {
/**
* Write data and grid to #out# according
* to the given data format. This function
- * simply calles the appropriate
+ * simply calls the appropriate
* #write_*# function.
*
* In case of gnuplot output, the
* usually has. At present the following
* formats are defined:
* \begin{itemize}
- * \item UCD: #.inp#
- * \item GNUPLOT: #.gnuplot#
- * \item POVRAY: #.pov#
+ * \item #ucd#: #.inp#
+ * \item #gnuplot# and #gnuplot_draft#:
+ * #.gnuplot#
+ * \item #povray#: #.pov#
* \end{itemize}
*
* Since this function does not need data