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Forum: Processes Involving Optical Photons
Re: None Optically conected volumes (Robert Penny)
Re: None RE: Optically conected volumes (Robert Penny)
Date: 25 Mar, 2010
From: Gumplinger Peter <Gumplinger Peter>

> I'd still like a clarification if possible.

> 1. Are surfaces between daughter volumes in the same parent volume just

> defined by their placements being such that two of their surfaces =

> overlap to within a certain geometric tolerance?

Two daughters of the same mother volume must NOT overlap! What you should do is calculate their position such that the flush surface you want exactly touches (within the precision of the computer calculation). The concept of 'touching' is of course within a computational tolerance; for details you need to consult documentation about G4's navigation and global/management/include/G4GeometryTolerance.hh - in general though, the user need not worry about these details, except for the requirement I stated above.

> 2.  Does this cause a geometry problem with possible overlap of bounding =
> surfaces when tracking other particles?

You dont' want overlaps in your geometry, irrespective of what particles you want to track.

3. Does the definition of a G4LogicalBorderSurface help the geometry or tracking manager solve this problem?

The G4LogicalBorderSurface is assigned to a ORDERED pair of physical volumes. The G4OpBoundaryProcess decides which BorderSurface to fetch from the two pointers it has to the physical volumes on either side of the boundary. Actually, you do not require a BorderSurface if all you want to take into account is Snell's Law between two dielectric media.

To summarize, the G4 navigator is capable of moving between two daughter volumes, and without jumping 'into a void' between them finding itself in the mother, so long as you have calculated the surface to coincide.

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