Hello, while trying to use TGeom (TNode,...) in AliRoot, I noticed a pb which can be seen in this basic macro: { gROOT->LoadMacro("loadlibs.C"); loadlibs(); TFile *file = new TFile("galice.root"); if (!gAlice) { gAlice = (AliRun*)file->Get("gAlice"); if (gAlice) printf("AliRun object found on file\n"); if (!gAlice) gAlice = new AliRun("gAlice","Alice test program"); } char namech[10]; char name[10]; sprintf(name,"SLAT_N%d",slatnum); // Converting local -> master Float_t local[3],local2[3], master[3]; local[0] = x1; local[1] = y1; local[2] = 0; TNode *node = gAlice->GetGeometry()->GetNode(name); node->UpdateMatrix(); node->Local2Master(local,master); cout<<"local "<<local[0]<<" "<<local[1]<<" "<<local[2] << endl; cout<<" master "<<master[0]<<" "<<master[1]<<" "<<master[2]<<endl; node->UpdateMatrix(); node->Master2Local(master,local2); cout<<"local2 "<<local2[0]<<" "<<local2[1]<<" "<<local2[2] << endl; } which give this outpout (this is not normal since we have to found the same starting and ending values...): local 10 3 0 master 75.7508 68.2644 986 local2 9.73511 3.77195 1.63918e-15 (int)1085958144 Maybe the same problem was describe in this ROOT Talk, but this question had no answear: From: Volker Hejny (V.Hejny@fz-juelich.de) Date: Tue Aug 28 2001 - 08:30:19 MEST Next message: Christian Holm Christensen: "Re: [ROOT] add histogram" Previous message: Rene Brun: "Re: [ROOT] add histogram" Messages sorted by: [ date ] [ thread ] [ subject ] [ author ] Hi all, I tried to use TGeometry and played with the transformation function Master2Local and Local2Master. While the latter worked properly, the other did not what I assumed. On closer look I found, that the same matrix is used as in Local2Master. Instead the transposed should be used. Best regards, Volker -- Dr. Volker Hejny Tel: 02461/616853 ** Institut f. Kernphysik Fax: 02461/613930 ** ---------------------------------------------------------------- ** ** --- Forschungszentrum Juelich GmbH, D-52425 Juelich ** Thanks a lot in advance, Eric
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