A connection between two parts in different rigid bodies is called 3D contact, where the contact is between a single surface or vertex in the first rigid body and one or more spherical, cylindrical, or planar surfaces or verteces from the second rigid 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.