|Message: Re: How to get the normal vector of crossing boundary?||Not Logged In (login)|
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On Wed, 13 Dec 2017 09:58:51 GMT, Yuto Minami wrote:
> In optical photon, UCN simulation, and phonon simulation, a unit vector > is got from the nearest surface to the post-step point at the > reflection. > > However, this would be wrong when the post-step point is not near to the > crossing boundary. Are there any way to get the normal vector of > crossing boundary?
Hi, Yuto. At a boundary-limited step (postStepPoint->GetStepStatus() == fGeomBoundary), the post-step position "must" always be on the boundary surface, and therefore getting the unit vector is almost perfectly well-defined (with the exception of a post-step point exactly on an edge or corner, where the tangent surface is undefined).
The problem, as we have discussed, is that in your application we are encountering rare situations in which the G4 tracking maybe doesn't "see" the boundary properly, and oversteps the track into the neighboring volume. In this case, the post-step position is not where it is "supposed to be" for a boundary-limited step, and of course the assumptions related to that will fail.
-- Mike Kelsey
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