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Dear David, As you see from the documentation we recommend that the geometry is free of overlaps. Since the geometry modeller is a complicated beast, if there is a way to avoid unnecessary overlaps, it could improve the robustness of the simulation. This concerns overlaps which involve a non-microscopic distance (e.g. an overlap of a few microns in a setup measuring 10 meters in diameter is tolerable, and likely will also occur due to imperfect floating point operations on rotation matrices. ) It is possible that creating non-overlapping versions of a few volumes will results in one or more solids (shapes) which are much more complicated. Then an argument can be made that it would be better (more robust) to live with a few small overlaps at a single level of the geometry. And when all volumes which overlap are filled with the same material (vacuum), it is reasonably likely that the simulation results would be unaffected by the overlap. If what you are asking though, is whether it is ok to introduce overlaps at several levels of the geometry (potentially for convenience or simplicity), then the answer is NO. The geometry modeller can become confused, and its answers cannot be guaranteed. And when you get navigation errors, then the geometry modeller (G4Navigator) will check whether your geometry has overlaps - and you will get error messages. We are not able to diagnose or help in case of problems caused by overlaps which the user has intentionally introduced into their geometry setup. I hope that this gives a measure of clarity. Best regards, John Apostolakis On 11/08/16 17:10, David Sarria wrote: > *** Discussion title: Geometry > > Hi all, > > I have a basic question about geometry. > > I want to place several copies of a detector unit. The parts of one > detector unit are daugther of a logical volume, that is a box slighly > larger than all the detector unit elements and filled with vacuum. > > When I place several times the detector units, some small parts of the > vacuum boxes overlap (but not the detector parts). Is it a problem ? > > And if some part of the vacuum box (not the detector parts) is > overlapping with some other physical surrounding elements ? > > Is there a way to place only the daughters but not the vaccum box ? > > Thanks in advance. > > David > > ------------------------------------------------------------- > Visit this GEANT4 at hypernews.slac.stanford.edu message (to reply or unsubscribe) at: > http://hypernews.slac.stanford.edu/HyperNews/geant4/get/geometry/1495.html
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