MREGION
Define a material region from a set of surfaces by logically combining the surface names and region names. A material region may be removed from the geometry by specifying the release keyword.

To define material rgion, the operator 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 regions or modified surfaces mean union, intersection and complement respectively. Parentheses are operators and are used for nesting. Spaces are required as delimiters to separate operators and operands; parentheses are operators and must be surrounded by spaces. Internal interfaces should be excluded when defining material regions. (i.e. use lt and gt ). External boundaries should be included when defining material regions. If a material regions consists of more than one region and the regions touch (i.e. share a region interface), then the region interface is not a material interface -- all the points on the region interface are interior to the material region. In this case use le or ge to include these region interface points in the material region as interior points.

Defining a material region will cause the information associated with this material region to be stored under the name of the geometry of the current mesh object.  Releasing the material region will remove this information.
 

 FORMAT:  mregion/material_region_name/region definition EXAMPLES: mregion/ material_region_name/release
mregion/mat1/ le box1 and ( lt sphere1 and ( lt plane1 or gt plane2 ) ) /
mregion/mat2/ regiona or regionb /