# Creation tools: references

## Reference

A reference entity provides some support to the construction of the geometry without being taken into consideration during the mesh and solving operations. These entities are of the « NO_EXIST » type.

There are several modes of creation of a « Reference » entity :

• Point of reference
• Line of reference defined between two points of reference (procedure of creation identical to a segment of a polyline)
Reference line Reference point

## Access / Cursor

The different accesses and the personalized cursor for this mode of creation are presented in the following table:

Type Access Cursor
Reference point By icon:
By menu: Construction → Reference → Reference point
Reference line By icon:
By menu: Construction → Reference → Reference line

## When do we use them?

The entities of reference can be used :

• During the construction of a symmetry in relation to a point of reference
• During the construction of a symmetry in relation to a line of reference
• During the construction of a circular repetition in relation to a point of reference
• During a rotation motion in relation to a reference point
• During a scaling in relation to a reference point
• Automatically, for the creation of an arc 2 points with centre point or a circle center + radius, the centre point is a reference point (if this is not an already existing point)

## Some rules

The entities of reference coexist with the standard entities « Point » and « Line ».

Certain coexistence rules have been set :

• The standard point has priority over the point of reference
• Upon the creation of a line of reference starting from a / or finishing on a standard point, the latter remains a standard point
• Upon the creation of a polyline/rectangle/arc/circle starting from a / or finishing on a point of reference, the latter is transformed into a standard point
• The line of reference can be created or displaced as a superposition to a line that is « standard » or « of reference » without operating the correction of superposition of the lines
• The point of reference can be created or disposed as a superimposition to a line that is « standard » or « of reference » without causing the fragmenting of the line
• The entities of reference are not affected by the actions of correction (intersection, superimposition)