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Forum: Geometry
Re: Question How to change threevector direction ? (Mustapha Assalmi)
Date: Mar 17, 10:03
From: michel maire <michel maire>

On Wed, 13 Mar 2019 21:37:46 GMT, Mustapha Assalmi wrote:
> Hi all, I want to reverse the direction of the Y axis in the phantom.
> can anyone help me? that picture to clarify the question well
> 
>    Attachment:
>       http://hypernews.slac.stanford.edu/HyperNews/geant4/get/AUX/2019/03/13/14.36-63707-medlic.png

 Rotate phantom alone would not solve your problem because the tracking of particles is done in "absolute" coordinates system, e.g. in the world frame, which will be unchanged.

 You must rebuilt your geometry with all source volumes placed at -y instead of +y. And shoot particles in direction (0, 1, 0)

  Another solution :   - keep your geometry unchanged
                       - define a SuperWorld with dimensions equal or bigger than your actual World
                       - place World within SuperWorld with a rotation of 180 deg around ox

  Something like :

 G4RotationMatrix rotm = G4RotationMatrix();
 rotm.rotateX(180*deg);
 G4ThreeVector position = G4ThreeVector(0., 0., 0.);
 G4Transform3D transform = G4Transform3D(rotm, position);

 new G4PVPlacement (transform, logicalWorld, "World", physicalSuperWorld, boolean=false, copyNumber=0);

 See in examples/extended/geometry/transforms various ways to define rotation matrix.

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1 None: Re: How to change threevector direction ?   (Mustapha Assalmi - Mar 20, 15:37)
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