4. Divide the enclosing volumes into regions

Theregion command is used to divide the enclosing volume into regions. The directional operators lt, le, gt, ** ** and ge are applied to previously defined surfaces according to the following rules.

lt – if the surface following is a volume then lt means inside not including the surface of the volume. If the surface is a plane or a sheet lt means the space on the side of the plane or sheet opposite to the normal not including the plane or sheet itself.

le – if the surface following is a volume then le means inside including the surface of the volume. If the surface is a plane or a sheet le means the space on the side of the plane or sheet opposite to the normal including the plane or sheet itself.

gt – if the surface following is a volume then gt means outside not including the surface of the volume. If the surface is a plane or a sheet gt means the space on the same side of the plane or sheet as the normal not including the plane or sheet itself.

ge – if the surface following is a volume then ge means outside including the surface of the volume. If the surface is a plane or a sheet ge means the space on the same side of the plane or sheet as the normal including the plane or sheet itself.

In region comands, surface names must be preceeded by a directional operator. The logical operators or, and, and not mean union, intersection and complement respectively. Parentheses are operators and are used for nesting. Spaces are required as delimiters to separate operators and operands. To define the two regions created by the plane bisecting the unit cube:

region/top/ le cube and gt cutplane /

region/bottom / le cube and le cutplane ** **/

The region bottom contains the interface cutplane; top contains none of the interface. Interior interfaces must be included in one and only one region.

If a region touches an external boundary, include the surface that defines the enclosing volume in region and mregion commands. For example, the regions top and bottom are enclosed by the surface cube

“344” “239”