Joint mechanisms can be scoped to either flexible or rigid parts (see Stiffness Behavior).
If the parts are considered Rigid, the scope of the joint (reference and/or mobile) will merge with the Rigid Body that is created.
If the parts are considered Flexible, a Remote Point will be created for the scoped nodes.
Multiple joints scoped to the same geometry (essentially overlapping Remote Points) are allowed by the Explicit solver. The solver will merge the underlying nodes in the scope into a single rigid body.
In theory, the mesh of Rigid Bodies can be defined as dimensionally reduced. However it is important that the scope of the joints to these Rigid Bodies is passed on to the solver. This means the scope needs to be meshed with elements. This can be accomplished by defining contact surfaces on the scope.
Note that non interpenetrating meshes are needed to warrant frictionless behavior.
If a part is not meshed at all the following error will be given:
This can be resolved by meshing a part of the geometry with elements.
Joints can only be scoped to Lagrange bodies, not Eulerian/Particle bodies.