petsc-master 2020-10-26
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# DMPlexCreateBasisRotation

Create an internal transformation from the global basis, used to specify boundary conditions and global solutions, to a local basis, appropriate for discretization integrals and assembly.

### Synopsis

```#include "petscdmplex.h"
PetscErrorCode DMPlexCreateBasisRotation(DM dm, PetscReal alpha, PetscReal beta, PetscReal gamma)
```

### Input Parameters

 dm - The DM alpha - The first Euler angle, and in 2D the only one beta - The second Euler angle gamma - The third Euler angle

Note: Following https://en.wikipedia.org/wiki/Euler_angles, we will specify Euler angles by extrinsic rotations, meaning that

### we rotate with respect to a fixed initial coordinate system, the local basis (x-y-z). The global basis (X-Y-Z) is reached as follows

\$ The XYZ system rotates about the z axis by alpha. The X axis is now at angle alpha with respect to the x axis. \$ The XYZ system rotates again about the x axis by beta. The Z axis is now at angle beta with respect to the z axis. \$ The XYZ system rotates a third time about the z axis by gamma.