CGX: Handling of missing geometry in path plots

[mkraska]

if the sampling points of a path plot happen to be outside the geometry, then these points are removed, no matter if they were based on line division or node selection.
If such nodes occure at the beginning or end of a path, then there is no problem. If the nodes are in a hole or gap in the geometry, then in the plot there is just a straight line connecting the proximal nodes with valid values.
See for example https://github.com/mkraska/CalculiX-Examples/tree/master/Linear/StressConc1#post-processing
In Gnuplot, you would just need an empty separator line to interrupt the graph. Such lines might be issued whenever there is an invalid data point.

[mkraska]

still persistent in 2.13.1