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Forum: Geometry
Re: None Volumes overlapping (C Mos)
Date: 26 Nov, 2012
From: Michael H. Kelsey <Michael H. Kelsey>

On Tue, 27 Nov 2012 03:36:56 GMT, C Mos wrote:
> Hi I was just wondering how bad could a simulation result in the case,
> for example two objects, belonging to the same mother volume, overlap in
> space. Would we be talking about unpredictable results?

Yes, the results are unpredictable. You can think simplistically in terms of a track: when it hits the overlapping region, which volume is the track in? Which material is supposed to be used for interactions?

With the way the geometry is optimized before the run starts, the overlap is even more problematic, since it essentially breaks the uniqueness of the search tree (I've oversimplified the description, of course).

> On the same token, does geant4 offer a function to check containment of
> one volume by another, referring to the simple cases of CGS solids?

Yes. You can do this programmatically, by passing "true" as the final argument to G4PVPlacement (immediately after the copy number). You can also call the CheckOverlaps() function of G4PVPlacement after instantiation.

There are also run-time (macro based) geometry tests available, such as |/geometry/test/grid_test 1|. This method is not as comprehensive, and is not recommended any longer.

            -- Michael Kelsey

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