#### 2.1.7.1. Geometrical Selection Rules

Figure : Definition of a Parallel Selection Rule

Parallel, Cylindrical, and Spherical Selection Rules are simple shapes which can be defined by a few parameters:

- Parallel: Defined by two parallel planes. The planes are defined by an origin, a normal vector and two distances (offsets of the planes from the origin along the normal vector).

- Cylindrical: The cylinder is defined by an origin and the vector of the axial direction and the radius. The cylinder has infinite height.

- Spherical: The sphere is defined by the center and the radius.

Figure : Example of a Parallel Selection Rule

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