GhostNodeElement

GhostNodeElement(ndof: int = 3, **kwargs)

Bases: Element

Virtual element that owns mesh nodes without creating OpenSees elements.

GhostNodeElement keeps nodes in the Femora mesh and Tcl export pipeline without emitting a structural element command. It is commonly used for center-of-mass nodes, control or reference nodes, and mass application points that should not participate in element stiffness.

Note

Each instance receives a unique sentinel ndf value so mesh merging does not combine ghost nodes with structural nodes or with one another. At export, the sentinel is mapped back to the real DOF count through resolve_ndf.
to_tcl returns a Tcl comment rather than an OpenSees element command; the owning nodes are still written by the export loop.

Example

from femora.core.model import Model

model = Model()
ghost = model.element.special.ghost_node(ndof=6)
print(ghost.real_ndof)

Create a GhostNodeElement with merge-protected sentinel DOF metadata.

Parameters:

Name	Type	Description	Default
`ndof`	`int`	Real number of DOFs per node written during Tcl export. Must be 3 or 6.	`3`
`**kwargs`		Additional keyword arguments forwarded to the base element constructor.	`{}`

Raises:

Type	Description
`ValueError`	If `ndof` is not 3 or 6.

Attributes

real_ndof `property`

real_ndof: int

Return the real DOF count written to the Tcl node command.

Methods:

resolve_ndf `classmethod`

resolve_ndf(ndf_value: int) -> int

Map a mesh ndf value to the real DOF count for Tcl export.

If ndf_value is a ghost sentinel, it is resolved through the internal map. Otherwise the input is returned unchanged.

Parameters:

Name	Type	Description	Default
`ndf_value`	`int`	Raw `ndf` value from mesh `point_data["ndf"]`.	required

Returns:

Type	Description
`int`	The real DOF count to write into the Tcl `node` command.

is_ghost_ndf `classmethod`

is_ghost_ndf(ndf_value: int) -> bool

Check whether an ndf value is a ghost-node sentinel.

Parameters:

Name	Type	Description	Default
`ndf_value`	`int`	The `ndf` value to inspect.	required

Returns:

Type	Description
`bool`	`True` if the value is a ghost-node sentinel.

GhostNodeElement