You can clearly see the sources of $x$-displacement around $x=0.5$ and
-$x=-0.5$, and of $y$-displacement at the origin. The next image shows the
-final grid after eight steps of refinement:
-
-<img src="https://www.dealii.org/images/steps/developer/step-8.grid.png" alt="">
-
+$x=-0.5$, and of $y$-displacement at the origin.
What one frequently would like to do is to show the displacement as a vector
-field, i.e., show vectors that for each point show the direction and magnitude
+field, i.e., vectors that for each point illustrate the direction and magnitude
of displacement. Unfortunately, that's a bit more involved. To understand why
this is so, remember that we have just defined our finite element as a
collection of two components (in <code>dim=2</code> dimensions). Nowhere have
quantities) but that the two components actually are the parts of a
vector-valued quantity, namely the displacement. Absent this knowledge, the
DataOut class assumes that all individual variables we print are separate
-scalars, and Visit then faithfully assumes that this is indeed what it is. In
+scalars, and Visit and Paraview then faithfully assume that this is indeed what it is. In
other words, once we have written the data as scalars, there is nothing in
-Visit that allows us to paste these two scalar fields back together as a
+these programs that allows us to paste these two scalar fields back together as a
vector field. Where we would have to attack this problem is at the root,
namely in <code>ElasticProblem::output_results()</code>. We won't do so here but
instead refer the reader to the step-22 program where we show how to do this
for a more general situation. That said, we couldn't help generating the data
anyway that would show how this would look if implemented as discussed in
-step-22. The vector field then looks like this (Visit randomly selects a few
+step-22. The vector field then looks like this (Visit and Paraview
+randomly select a few
hundred vertices from which to draw the vectors; drawing them from each
individual vertex would make the picture unreadable):