LaGriT/documentation/lagrit_manual/commands/region.txt

.. _region :

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> **_REGION_**

>

>> Define a geometric region from the set of surfaces by logically combining
the surface names.&nbsp_place_holder; A region may be removed from the
geometry by specifying the release keyword.

>>

>> To define a region, the 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.   
The operators or, and, and not applied to surfaces mean union, intersection
and complement respectively. The parentheses operators, (and ), are used for
nesting. Spaces are required as delimiters to separate all operators and
operands. Internal interfaces should be included in exactly one region. In the
event of conflicting region commands, the one occurring last in the input
stream takes precedence.

>>>

>>> Defining a&nbsp_place_holder; region will cause the information associated
with this material region to be stored under the name of the [geometry
](../geometries.html)of the current mesh object.&nbsp_place_holder; Releasing
the&nbsp_place_holder; region will remove this information.

>

> FORMAT:

>

>> **region/**region_name/region definition

**region/**region_name/**release**   
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>

> EXAMPLES:

>

>> **region**/reg1/**le** sphere1 **and** ( **lt** plane1 **or** **gt** plane2
)

**region**/reg2/**le** sphere1 **and** ( **ge** plane1 **and** **le** plane2 )   
**region**/reg1/**release**   
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