Facet selection groups
If you have carefully selected a group of facets, let\'s say walls of a pipe, then you probably won\'t want to select them once again.
That\'s why the Memorize selection function was added, allowing you to create facet groups, which are saved with the geometry file. Selection groups have other advantages as well: you can count the sum and average of physical quantities on them in the Formula Editor, and you can change their physical parameters with the command line interface
To create a selection group, select some facets, then use Selection menu / memorize selection (shortcut: CTRL+W), and give your selection a name.
Then you can select this group again using the Selection menu, or more quickly by the ALT+1, ALT+2, ... combinations for facet groups #1, #2, ... respectively.
You can also combine selection groups: SHIFT+ALT+1 (or holding SHIFT and selecting Selection/Select memorized/first group) will add selection group 1 to the existing selection. Intuitively, CTRL+ALT+1 will remove selection group 1 from the actual selection.
Formulae with selection groups
In SUM and AVG formulae you can refer to the selection groups by their number:
In the screenshot above
SUM(H,S1)summarizes the Monte Carlo hits (H) on selection group 1AVG(P,S1)averages (weighed by area) the pressure (P) on selection group 1