Boolean selections — Union Selection (), Intersection Selection (), Difference Selection (), and Complement Selection () — are useful to combine two or more selections (union), create a selection of entities that are common to the input selections (intersections), create selection of entities that are in one selection but not in another (difference), and to create a selection as the complement (inverse) of one or more selections (all boundaries except the inflow boundaries, for example). The complement can be convenient if a selection is needed that consists of all boundaries except one or a few. Then it is easier to first create a selection (just the one boundary, for example) and then use a Complement node to create its complement. All Boolean selection nodes’ Settings windows have similar sections. To add this node, right-click the Geometry node and choose an option from the Selections menu.

Based on space dimension, select a Level — Object, Domain, Boundary, Edge (3D only), or Point for the selections to add or remove from the Selections to add (Selections to intersect, Selections to subtract, and Selections to invert) list.

Use the buttons in this section to move, add, or delete selections in the Selections to add (Union), Selections to intersect (Intersection), or Selections to invert (Complement) lists. For the Difference selection node, also choose Selections to subtract. Click the Add button () to open an Add dialog box that contains all existing selections for the same geometric entity level. Use the Move Up (), Move Down (), and Delete () buttons to organize the list.

This section contains settings for controlling if the resulting selection should contribute to a cumulative selection and if it should be kept and shown. From the Contribute to list, choose an option. In addition to available Cumulative Selection nodes, None is always available from the list. To create a new Cumulative Selection, click New. Enter a Name in the New Cumulative Selection window. Click OK or press enter. This new cumulative selection is now available from any Contribute to list for a geometry selection.

By default, the Keep selection check box is selected. Clear the check box if you do not want the resulting selection to be available as a named selection in other nodes in the geometry sequence or other parts of the model tree. If the Keep selection check box is selected, you can also determine if the selection should appear in applicable settings for physics, materials, and other parts of the model tree outside of the geometry using the Show in physics list (or Show in instances if the selection is in a geometry part; Show in 3D in a plane geometry under a work plane in a 3D component). If the geometric entity level is not set to Object (and of Domain, Boundary, Edge, or Point), choose On (the default) or Off to show the selection in physics and other settings or not. If the geometric entity level is Object, choose one of All levels (that is, all entity levels), Object selection (in geometry parts only), Domain selection, Boundary selection, Edge selection (3D only), Point selection, or Off. For Show in physics, All levels is the default; for Show in instances, Object selection is the default.