# Contact Constraints

Contact-type constraints can be created between two directed surfaces. Directed means that an internal side and an external side can be defined from a geometrical element, a face of a pad for example. This definition excludes surface element and wireframe surface because they are not directed.
The common area between the two elements can be a plane (plane contact), a line (line contact), a point (point contact) or a circle (annular contact).
The following table shows the elements you can select for a contact constraint.

 Plane Cylinder Sphere Cone Circle Plane NA NA Cylinder (1) NA NA NA Sphere NA (2) (4) (4) Cone NA NA (3) (4) Circle NA NA (4) (4) NA

• NA: Not Applicable.
• Plane: a plane or a planar surface for example.
• : surface contact.
• : line or annular contact.
• : point contact.
• (1) A cylinder-cylinder surface contact is possible when their radius are equal only.
The contact constraint resulting is equivalent to a coincidence constraint, cylinders look like merged.
• (2) A sphere-sphere surface contact is possible when their radius are equal only.
The contact constraint resulting is equivalent to a coincidence constraint, spheres look like merged.
• (3 A cone-cone surface contact is possible when their angles are equal only.
The contact constraint resulting is equivalent to a coincidence constraint, cones look like merged.
• (4) annular contact.

Important: The contact constraint is resolved using the mathematical and unlimited definition of the selected geometries and not the selected geometries themselves. Due to this definition, the contact constraint is not necessarily positioned according to the selected geometries, and can be
positioned outside of their contact area in 3D.