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## Re: How to change threevector direction ?

Forum: Geometry
Re: 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 Re: How to change threevector direction ?   (Mustapha Assalmi - Mar 20, 15:37)
 to: "Re: How to change threevector direction ?"
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