# struct.node.surface.xdir

Syntax

b := struct.node.surface.xdir(sn,v)

Set the orientation of the surface system of node sn such that the $$x$$-direction is aligned with the projection of the surface vector v onto the normal plane, which is defined by the $$z$$-direction. This operation can only be performed upon nodes that have a valid surface system (to ensure that the $$z$$-direction always corresponds with the average normal direction of at least one of the shell-type SELs using the node). A return value of true indicates success and false indicates failure.

Returns: b - boolean flag: true indicates success, and false indicates failure sn - structure node pointer v - vector