====== Defining contact elements ======

Defining contact element is done is the same way as volume elements. First, a contact material is defined (without friction, sticking, ...), then the material is included in an ''ElementProperties'' (''Contact2DElement'' ou ''Contact3DElement''), elements which are finally generated over the mesh with contact interactions (rigid-defo, defo-defo, ...).

===== Materials =====

First, a contact material:

  materialno = materialset.define (number, type)
  materialno = materialset(number)
  materialno.put(param, value)
  materialno.depend(param, fct, Key(Lock)))
  ...

|''number'' | contact material number (must be unique for all element in ''materialset'', not just for contact materials) |
|''type'' | type of contact material (for example ''FrictionlessContactMaterial'') - see [[doc:user:elements:contact:laws]] |
|''param'' | name of a contact parameter (for example ''PEN_NORMALE'') |
|''value'' | value of the corresponding parameter|
|''fct'' | function which characterizes the dependency of the property (optional: no ''fct'' if no dependency) |
|''Lock'' | [[doc:user:general:locks|Lock]] which defines the dependency variable of the property (compulsory if there is a dependency) |

All contact materials and corresponding parameters are found page [[doc:user:elements:contact:laws]].

===== Elements =====

Second, contact elements are defined with ''ElementProperties'', and the contact material is included.

  prp = ElementProperties(typeEl)
  prp.put(param1, value1)
  prp.depend(param1, fct1, Lock1)) #optional
  ...
    
where

|''typeEl'' | desired contact element (for example ''Contact[2|3]DElement'')|
|''param1''| name of the property associated to the element (for example ''MATERIAL'' to associate the desired material)|
|''value1''| value of the corresponding property |
|''fct1''| function which characterizes the dependency of the property (optional: no fct if no dependency) |
|''Lock1''| [[doc:user:general:locks|Lock]] which defines the dependency variable of the property (compulsory if there is a dependency) |

Contact elements and their parameters are found page [[doc:user:elements:contact:elements]].

===== Interactions =====

Finally, contact elements are generated using ''Interactions''. Several interactions exist, depending on the type of contact (rigid-defo, defo-defo, ...). These interactions are the code used to generate them are found page [[doc:user:elements:contact:interactions]].

For example, to generate rigid-defo contact, ''RdContactInteraction'' is used :

  ci = RdContactInteraction(number)
  ci.setTool(gObject1)
  ci.push(gObject2)
  ci.setSmoothNormals(bool)
  ci.addProperty(prp)
  interactionset.add(ci) 

where

| ''number'' | number of the ''Interaction''|
| ''gObject1'' | Reference of a geometric object (facetised contact), meshed or not|
| ''gObject2'' | Reference of a meshed geometric object|
| ''prp'' | [[doc:user:elements:general:def_element_properties|Properties]] of [[doc:user:elements:contact:elements|contact elements]] to generate |
| ''setTool'' | Rigid tools |
| ''setSmoothNormals(bool)'' | Facetised tool\\ = True (default) : continuous normal - projection on a ''[[doc:user:geometry:user:contours#remarques|MultiProjWire]]'' or ''[[doc:user:geometry:user:peaux#remarques|MultiprojSkin]]''\\ = False : discontinuous normal -  projection on ''[[doc:user:geometry:user:contours|Wire]]'' or  ''[[doc:user:geometry:user:peaux|Skin]]''|