## Transformation matrix

**This issue was created automatically from an original Mantis Issue. Further discussion may take place here.**

Request from one of my users:

The transformation matrix is a 3x3 matrix of the direction cosines that is used to transform nodal fields like displacement to a rotated coordinate system. Thus, the analyst may want to have the displacement or acceleration in another frame. A common case for structural dynamics is transformation of a modal test where an accelerometer may be reporting the acceleration in the direction of it's orientation (e.g. it may by glued to a wing of a wind turbine). Element variables (such as strain gauge output) may also be so transformed.

For cartesian coordinate systems, the transformation matrix is just the 3x3 matrix of direction cosines. The coordinate frame information in the exodus file has an origin and the direction cosines of the Z and X directions. The Y direction is obtained by the right hand rule.

Curvilinear coordinates such as the cylindrical and spherical frame actually have a transformation matrix that depends on the point of evaluation. Thus, the direction cosines of a cylinder change as you evaluate points around the cylinder. I'm not sure of the best way to generate a user interface for this. Essentially the analyst needs to provide the coordinate frame and the location for evaluation. Again, the 3x3 matrix of direction cosines is the output.

Also, the customer would not mind consulting with the implementer.