A rope joint enforces a maximum distance between two points on two bodies. It has no other effect. Warning: if you attempt to
change the maximum length during the simulation you will get some non-physical behavior. A model that would allow you to
dynamically modify the length would have some sponginess, so I chose not to implement it that way. See b2DistanceJoint if you
want to dynamically control length.
Fields inherited from class com.badlogic.gdx.physics.box2d.Joint