#### 2.1.8.1. Reference Direction

The Reference Direction can be defined by Rosettes or from tabular values. A single Rosette is sufficient for the definition of the Reference Direction. Multiple Rosettes can be selected for one Oriented Selection Set to obtain complex Reference Direction definition. In this case, a Selection Method must be used to determine which Rosette is applicable to what part of the Element Set. The Selection Method offers several interpolation algorithms listed below:

- Ansys Classic: Coordinate system is projected on the elements as defined in ANSYS (see Coordinate Systems).

- Maximum Angle: Coordinate system in which the Z direction has the maximum angle with the element orientation defines the Reference Direction of the Oriented Selection Set.

- Maximum Angle Superposed: Same as Maximum Angle but all the chosen coordinate systems are considered and weighted by the maximum difference angle direction.

- Minimum Angle: Coordinate system in which the Z direction has the minimum angle with the element orientation defines the Reference Direction of the Oriented Selection Set. (default)

- Minimum Angle Superposed: Same as Minimum Angle but all the chosen coordinate systems are considered and weighted by the minimum difference angle direction.

- Minimum Distance: Nearest coordinate system of the element defines the Reference Direction of the Oriented Selection Set

- Minimum Distance Superposed: Same as Minimum Distance but all the chosen coordinate systems are considered and weighted by the distance to the element.

- Tabular Values: Interpolated from the values put in a Look-up Table. The table must include the location values and a direction column.

Note: If the determination of an element's Reference Direction fails, an alternate computation method is used and a warning is issued. In this case, it is recommended to verify the Reference Directions of the affected Oriented Selection Set.

The bonding laminates of the T-Joint example are a case where a Minimum Angle Selection Method is suitable.

Figure : Reference Direction of a Bonding Laminate Defined by Two Rosettes and a Minimum Angle Selection Method

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