This data item defines a spherical segment in space.
Other data items can check if nodes are located on this geometry.
The coordinate of the center is *x_c y_c z_c*.
If *side_x* is set to a positive value, say +1.,
then only x-values larger then *x_c* are considered
to be part of the geometry.
If *side_x* is set to a negative value, say -1.,
then only x-values smaller then *x_c* are considered
to be part of the geometry.
If *side_x* is set to 0 ,
then all x-values are considered
to be part of the geometry.
Likewise remarks hold for y- and z-values.

All **node** within a distance *tolerance* of *radius*
are considered to be part of the spherical segment.

tochnog 2001-09-02