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4. Divide the enclosing volumes
into regions
The region 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
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