I.4.6.7 “modifyRefCoordSys”

“modifyRefCoordSys” is used to modify the reference coordinate system wrt which the components of a vectorial or a tensorial Result are applied. If the Result is vectorial it can represent any vectorial quantities except the coordinates. For coordinate vectorial Result, the method “modifyPositionRefCoordSys” must be used. This method has no effect on scalar Results.

The methods returns nil (no new Result object is created) and takes two, three or five arguments:

1.

A DataBase object.

2.

An object corresponding to the definition of the coordinate system to which one switches. This object may have different types:

(a)

A String object with one of the following values: “elemCS”, “nodeCS”, “matCS”, “plyCS”, “elemIJK”, “lamCS”. All those coordinate systems are local to an element or to a node.

More information about the peculiarities of “matCS”, “plyCS” and “lamCS” coordinate system transformations is given in section X.B.5.

(b)

The argument may by a CoordSys object. Then it must be defined wrt a coordinate system defined in the DataBase argument.

(c)

The argument may by a Results object. This should then be a FieldCS Result. (See I.4.1.5.)

(d)

The argument may also be an integer larger than or equal to 0. Then the coordinate system must be defined in the DataBase.

3.

The third argument is the direction vector used to build the projected coordinate system on surfacic elements. The vector is given by an Array of three real objects, and is expressed wrt to the coordinate system given in second argument. If one does not wish to transform into a projected coordinate system, then the third argument must be omitted or nil. (However if arguments 4 and 5 are provided, the third argument cannot be omitted.)

4.

An object corresponding to the definition of the coordinate system from which one switches. This object may have the same values as the second argument.

5.

The last argument is a direction vector used to build the projected coordinate system on surfacic elements. The vector is given by an Array of three real objects, and is expressed wrt to the coordinate system given in second argument. If one does not wish to transform into a projected coordinate system, then the third argument must be nil.

The reason why a DataBase object is given as argument is that for curvilinear coordinate systems, much information about the location of Result value is necessary to perform a correct transformation of the components. Also, all coordinate systems are stored in the DataBase object. Therefore, it is very important that the programmer keeps in mind that all Results are related to a DataBase.

Note that some transformation vectorial or tensorial coordinate systems cannot be reversed. For example, once a Result is expressed in a projected coordinate system. Also, if a conversion has been done in a coordinate system that is not defined in the DataBase, the conversion is impossible. After transformation, the coordinate system referenced in Result values is altered (section I.4.1.2).

If arguments 4 and 5 are provided, the method assumes that the values are expressed in that coordinate system definition. This means that the CsId found in each pair “key-values” pair of the Result object is totally disregarded. The use of arguments 4 and 5 may allow the modification of Results expressed in a user or projected coordinate system.

More information on the transformation of coordinate systems is given in section X.B.4.

This method can be used with Real Results as well as with Complex Results and returns the modified “Result” object.