|Message: Re: Direction of rotation - clockwise or counterclockwise||Not Logged In (login)|
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On Thu, 02 Apr 2015 13:18:16 GMT, Patrik Eschle wrote:
> Hello > > Now the confusion is complete. Two seemingly equivalent methods rotate > in different sense. > > But then Michel Maire points me to examples/extended/geometry/transforms.
Readme of the example does not explain enough the underlying motivations for the this exercise. Let me try to do it here.
1 - There are 2 constructors to place volumes : - G4PVPlacement ( G4Transform3D( rotmA, transl), ... - G4PVPlacement ( rotmB, transl, ... rotmA and rotmB must be mutually inverse. The question is : what is exactly the definition of rotmA (and therefore rotmB). This is what the first two methods try to explicit : rotmA is what I call direct matrix; rotmB is its inverse.
2- Operators AxialRotation. The function rotateY (or Z) build a direct matrix, e.g. rotmA Its inverse can be calculated as : rotmA_inv (theta) = rotmA(-theta) (Lie group ....)
This is what we wanted to illustrate in PlaceWithAxialRotations(). The first object is placed with rotmA, the second object with rotmB
3- Unfortunatly, constructor of rotation matrix with Euler angles choose the opposite convention (inconsistency in clhep) but I guess no one use Euler angles constructor.
Hope this can help. Michel
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