Dear all, it seems there is a numerical error in creation of TGeoArb8 shapes of the tetrahedron form.
I can reproduce it by following script
void tet()
{
gSystem->Load("libGeom");
TGeoManager *geom = new TGeoManager("World","IES");
//--- define some materials
TGeoMaterial *matVac = new TGeoMaterial("Vacuum", 0,0,0);
//--- define some media
TGeoMedium *Vac = new TGeoMedium("Vacuum",0, matVac);
//--- make the top container volume
TGeoVolume *world = geom->MakeBox("World", Vac, 200., 200., 200.);
world->SetLineColor(kMagenta);
geom->SetTopVolume(world);
// make the Arb8
Double_t dz = 40.26756400448;
Double_t vertices[8][2];
vertices[0][0] = 37.84736541792;
vertices[0][1] =-71.19994408747;
vertices[1][0] = 18.87610664352;
vertices[1][1] =-78.54945010802;
vertices[2][0] =-6.436485069432;
vertices[2][1] = 67.18916461673;
vertices[3][0] = 37.84736541792;
vertices[3][1] =-71.19994408747;
vertices[4][0] =-50.28698699201;
vertices[4][1] = 82.56022957875;
vertices[5][0] =-50.28698699201;
vertices[5][1] = 82.56022957875;
vertices[6][0] =-50.28698699201;
vertices[6][1] = 82.56022957875;
vertices[7][0] =-50.28698699201;
vertices[7][1] = 82.56022957875;
TGeoShape *TetShape = new TGeoArb8(dz, (Double_t*) vertices);
TGeoVolume *tetVac = new TGeoVolume("tetrahedron", TetShape, Vac);
tetVac->SetLineColor(kBlue);
// assemble the geometry
world->AddNode(tetVac, 0);
//--- close the geometry
geom->CloseGeometry();
//--- draw the ROOT box.
//geom->SetTopVisible();
geom->SetVisLevel(4);
world->Draw("ogle");
geom->Export("Tetrahedron.root");
}The points on the top face are the same.
root output:
Processing tet.C…
Info in TGeoManager::TGeoManager: Geometry World, IES created
Info in TGeoManager::SetTopVolume: Top volume is World. Master volume is World
Info in TGeoNavigator::BuildCache: — Maximum geometry depth set to 100
Fatal in TGeoArb8::ComputeTwist: Shape TGeoArb8 type Arb8: Lower/upper faces defined with opposite clockwise
aborting
Thread 1 (process 22645):
#0 0x00007fff85ae36ac in wait4 ()
#1 0x00007fff8776203a in system ()
#2 0x00000001042fe30f in TUnixSystem::StackTrace ()
#3 0x000000010425e5a6 in DefaultErrorHandler ()
#4 0x000000010425ea62 in ErrorHandler ()
#5 0x000000010426e366 in TObject::Fatal ()
#6 0x000000010583324e in TGeoArb8::ComputeTwist ()
#7 0x0000000105832e6d in TGeoArb8::TGeoArb8 ()
#8 0x0000000105978fd2 in G__G__Geom1_236_0_4 ()
#9 0x0000000104a0f705 in Cint::G__ExceptionWrapper ()
#10 0x0000000104aa469f in G__execute_call ()
#11 0x0000000104aa4c6c in G__call_cppfunc ()
#12 0x0000000104a83d9b in G__interpret_func ()
#13 0x0000000104a6e58e in G__getfunction ()
#14 0x0000000104aa25d9 in G__new_operator ()
#15 0x0000000104a57761 in G__getexpr ()
#16 0x0000000104a4bdd1 in G__define_var ()
#17 0x0000000104ac95df in G__exec_statement ()
#18 0x0000000104a85dd8 in G__interpret_func ()
#19 0x0000000104a6ef1b in G__getfunction ()
#20 0x0000000104a63f5a in G__getitem ()
#21 0x0000000104a630b9 in G__getexpr ()
#22 0x0000000104a57020 in G__calc_internal ()
#23 0x0000000104ad4594 in G__process_cmd ()
#24 0x00000001042cd1de in TCint::ProcessLine ()
#25 0x00000001042cd643 in TCint::ProcessLineSynch ()
#26 0x000000010424a862 in TApplication::ExecuteFile ()
#27 0x000000010424a047 in TApplication::ProcessLine ()
#28 0x00000001051073ea in TRint::Run ()
#29 0x000000010423dabf in main ()
Adding small number ~ 1e-10 to any top vertex solves the problem
but it not pleasant. Later I am creating thousands of tetrahedrons and assemble them all together in one geometry.
I am using
-
* -
W E L C O M E to R O O T * -
* - Version 5.34/04 10 January 2013 *
-
* - You are welcome to visit our Web site *
-
[root.cern.ch](http://root.cern.ch) * -
*
ROOT 5.34/04 (tags/v5-34-04@48259, Jan 10 2013, 17:15:27 on macosx64)
CINT/ROOT C/C++ Interpreter version 5.18.00, July 2, 2010
Cheers, A.