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## Re: How to get the normal vector of crossing boundary?

Forum: Event and Track Management
Re: How to get the normal vector of crossing boundary? (Yuto Minami)
Re: Re: How to get the normal vector of crossing boundary? (Michael H. Kelsey)
Date: 13 Dec, 2017
From: Yuto Minami <Yuto Minami>

 Hi Mike, Thank you for your reply. ```> 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). ``` I understand that the distance to the surface is calculated by DistanceToIn and the step length is the distance. Therefore, as you said, the exit normal should be the correct unit vector. ```> > 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. ``` It seems. I just wanted to know why such rare event happened and how I can get the information of crossing boundary. Anyway, as you said, if the point is on and edfe or corner, any method doesn't seem to work well. Thank you, Yuto

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1 Re: How to get the normal vector of crossing boundary?   (Mike Kelsey - 13 Dec, 2017)
 to: "Re: How to get the normal vector of crossing boundary?"
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