GetOrigin after a translation

ROOT
1

Hey,

I try to get the coordinates of the center of a volume after a TGeoTranslation. But when I use the method GetOrigin it´s always return (0, 0, 0)… I think that GetOrigin return the origin of this volume but before the translation, I mean when it was created around the origin.

[code]
TGeoVolume *myBox = MakeBox(“myBox”, 0, 4, 4, 5 );
SetTopVolume(myBox);

myVolume= new TGeoVolume(“myvolume”, new TGeoBBox(2, 1, 0.5)); //volume is created around the origin

myBox->AddNode(myVolume, 1, new TGeoTranslation(1, 0, 1)); // this volume is translated

// I need the coordinates of the “center” of myBox after the translation

TGeoBBox panBox = (TGeoBBox)(myBox->GetShape());
Double_t OX=(panBox->GetOrigin()) [0];
Double_t OY=(panBox->GetOrigin()) [1];
Double_t OZ=(panBox->GetOrigin()) [2];
cout << " myBox origin " << OX << " " << OY << " " << OZ << endl;[/code]

Any help would be greatly appreciated

Thanks

2

Hi,

GetOrigin returns the origin coordinates of the local reference frame of the bounding box of any shape/volume. The transformation you use to position this volume just defines the position of the volume frame with respect to its parent. So the behavior you get is normal.

Cheers,

3

If what you want is to get the coordinates with respect to the mother volume origin, the following seems to work for me:

will show you the TGeoMatrix* used to place this node within its mother volume. Which gets you one level above where you were.

If you want coordinates with respect to the top volume origin, I think you want to get the TGeoHMatrix from the TGeoPhysicalNode. I think here you have to know the path from top to the final volume, e.g. something like “TOP/A_1/B_2”.

Joe