With this option you can use a 2d beam in a 3d calculation.
With *first_direction* and *second_direction* you can set
the plane in which the beam will act;
set these to either **-x**, **-y** or **-z**;
set first the smaller one (so e.g. **-x** before **-y**).

Example of beam acting in x-z plane:

...

number_of_space_dimensions 3

materi_velocity

materi_velocity_integrated

materi_stress

end_initia

...

group_beam_inertia 0 ...

group_beam_plane 0 -x -z

...

end_data

Please realize that the beam mechanically still is a 2d beam (it does not model double bending or torsion); it just can act in a 2d plane in 3d space.

Any element output like **element_beam_direction** and
**element_beam_moment** is defined in the plane of the beam.

If this record is not specified for a beam in 3d,
then **-x** **-y** is assumed.
In 2d, this record cannot be specified (the beam is always in the x-y plane).

The *index* specifies the element_group, see **element_group**.