Created attachment 467 [details] minimal example Using Geant4 10.3p1 (I did not try other versions) I cannot draw twisted solids with a negative twist angle. The attachment contains a minimal example trying to draw a G4TwistedBox with a negative twist angle. It can be compiled with the command: g++ test.cc -o test `geant4-config --cflags --libs` The example crashes with the message [...] Polyhedron::SetReferences: different edge visibility 1/1/56 and 1/0/-1541871320 Polyhedron::SetReferences: different edge visibility 1/3/56 and 1/2/-1541871320 Segmentation fault (core dumped) If in line 15 the twist angle is made positive, the example runs without an issue. I also could not draw G4TwistedTubs and G4TwistedTrap with a negative twist angle, in these cases the test just crashes without any message.
Thanks for reporting this. I can see the problem. We will look into it.
A fix has been found and will be part of the next release. The problem only affected visualisation. Tracking is and was OK (tested with RayTracer). It is a relatively small fix - see below - which you may apply yourself if you have the ability to rebuild Geant4. Index: src/G4TwistedTubs.cc =================================================================== --- src/G4TwistedTubs.cc (.../geom-specific-V10-03-12) (revision 105798) +++ src/G4TwistedTubs.cc (.../geom-specific-V10-03-13) (revision 105798) @@ -906,11 +906,12 @@ { // number of meshes // - G4double dA = std::max(fDPhi,fPhiTwist); + G4double absPhiTwist = std::abs(fPhiTwist); + G4double dA = std::max(fDPhi,absPhiTwist); const G4int k = G4int(G4Polyhedron::GetNumberOfRotationSteps() * dA / twopi) + 2; const G4int n = - G4int(G4Polyhedron::GetNumberOfRotationSteps() * fPhiTwist / twopi) + 2; + G4int(G4Polyhedron::GetNumberOfRotationSteps() * absPhiTwist / twopi) + 2; const G4int nnodes = 4*(k-1)*(n-2) + 2*k*k ; const G4int nfaces = 4*(k-1)*(n-1) + 2*(k-1)*(k-1) ; Index: src/G4VTwistedFaceted.cc =================================================================== --- src/G4VTwistedFaceted.cc (.../geom-specific-V10-03-12) (revision 105798) +++ src/G4VTwistedFaceted.cc (.../geom-specific-V10-03-13) (revision 105798) @@ -1152,7 +1152,8 @@ { // number of meshes const G4int k = - G4int(G4Polyhedron::GetNumberOfRotationSteps() * fPhiTwist / twopi) + 2; + G4int(G4Polyhedron::GetNumberOfRotationSteps() * + std::abs(fPhiTwist) / twopi) + 2; const G4int n = k; const G4int nnodes = 4*(k-1)*(n-2) + 2*k*k ;
