A connection between two parts in different bodies is called 3D contact, where the contact is between a single surface or vertex in the first body and one or more spherical, cylindrical, or planar surfaces or verteces from the second body. You can define 3D contact between sphere-sphere, sphere-plane (or plane-sphere), cylinder-cylinder (or plane-cylinder), or cylinder-plane pairs as shown below. However, you cannot define 3D contact between a plane-plane or sphere-cylinder pair.

When you select a vertex as a 3D contact surface, a sphere is displayed around it. The vertex is handled as if it were a sphere:

Although 3D contacts are not genuine connections, they share many similar properties with other connection types. They are visible in the Model Tree under Connections and can be used as a connection when defining measures, snapshots and analysis constraints.

You can use the 3D contact measure to define pressure angles, contact areas, and slip velocity properties. During a kinematic drag, collision detection is enabled between 3D contact parts. 3D contacts are also visible as features in the Assembly Model Tree.