Regions in Three Dimensions

The concept of a REGION in 3D domains retains the same character as for 2D domains. 

The REGION is a partition of the 2D projection of the figure, and is extruded into the third dimension according to the EXTRUSION specification.

A material compartment in 3D is uniquely defined by the REGION of the projection which bounds it, and the LAYER of the extrusion in which it resides.

For further discussion of the 3D extensions of the BOUNDARIES section, see the User Guide chapter Using FlexPDE in Three-Dimensional Problems.