I have some problems using TGeoRotation. In the documentation it is stated that one gives the euler angles phi,theta,psi. This would correspond to, according to parts of the documentation, a rotation phi around z, a rotation theta around y’ and a rotation psi around z’’ (i.e. eurler angles). Other places in the documentation suggest that theta is around x’ axis, that is, not euler angles. I get results that suggest that the second rotation is around the first y-axis, i.e. y, not y’!!! Could anyone enlighten me on how the angles in TGeoRotation really are defined???
The Euler angles are used as in the “X-convention”. There are several conventions based on Euler’s theorem (see: http://mathworld.wolfram.com/EulerAngles.html).
The first angle is the rotation angle about Z, the second one is a rotation about the new X and the final a rotation about the new Z (as described in the Users Guide)
Thanks for the answer. Now I think things work.
The documentation of the constructor is still wrong. It says theta is about y’ axis, when it is in fact about x’ axis. Took me a while to figure this out. The comment in the constructor should be fixed.