Performing Boolean Operations on Regions

Boolean operations can be performed between two or more intersecting, closed, manifold regions to create a single region made up of a single surface. The new surface is also closed and manifold and can be used as part of the meshing process or as the starting point for additional Boolean operations.

This capability is useful when you import several separate components as regions and you require to join them together without losing any definition (as would occur if you use the surface wrapper). This capability, however, should not be used as a substitute for CAD Boolean operations. If you have access to the CAD data or parts, it is strongly recommended that you perform the Boolean operations as part of the Parts-Based Meshing pipeline.

The quality of the input surfaces is not important as long as the individual regions are closed and manifold. However, non-manifold baffles are permitted, provided the baffle boundary has been converted to an interface. The tessellated surfaces generated during the import of neutral and native CAD data files are adequate starting points in this respect. The new boundary triangles that are added as part of the process are usually of relatively poor quality, so it is recommended that you use the surface remesher to improve the overall quality before performing the volume meshing step.

If the input surfaces are not intersecting (for example, a box within a box) then a Boolean operation should not be performed and an alternative approach is required to setup up the regions for meshing.

In situations where two closed surface volumes do not intersect but have co-planar boundaries, then the surface Boolean operations should not be used. If one or more of the surfaces are not closed then the boundary merge operation should be used instead, which allows unclosed surfaces to be intersected with one another.

To perform a Boolean operation on regions:

1. Multi-select the regions that you want to include in the Boolean operation.
2. Right-click on one of the selections and choose Boolean > [Boolean Operation].
   The following Boolean operations are supported with regions:

   • Unite Regions — joins together two or more intersecting closed volume surfaces into one closed, manifold surface.
     
     
   • Intersect Regions — extracts the common volume that is shared between two or more closed volume surfaces.
     
     
   • Subtract... — removes one or more intersecting closed volume surfaces from another closed volume surface. When two regions intersect one another, then either region 1 can be subtracted from region 2 or vice versa, which can lead to two different results. The choice of which body to subtract is provided during this process.
     • Region 2 subtracted from Region 1:
       
       
     • Region 1 subtracted from Region 2:
       
       

   The Boolean operation is performed on the input regions and feedback is provided in the Output window.

Each input region can contain one or more boundaries. However, depending on the Boolean type selected and the shape of the geometries, existing boundaries may be deleted in the resultant surface.