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Agree Re: Solids whose surface is described by a set of coordinates 

Forum: Geometry
Re: Question Solids whose surface is described by a set of coordinates (Maura E.M.)
Date: 27 Apr, 2016
From: Michael H. Kelsey <Michael H. Kelsey>

On Wed, 27 Apr 2016 00:55:22 GMT, Maura E.M. wrote:
> Dear GEANT4 geometry experts, I got my first my first modeling
> challenge. I was given the drawings describing accurately a Linac
> Flattening Filter that is usually loosely modelled as a cone sitting on
> a small cylinder. I am requested to model it as from the drawings where
> the external surface profile is defined by an ordered set of (x,y)
> coordinates (plase, see attachment).

I agree with John Apostolakis here, G4Polycone is exactly the class to implement what you describe. You provide a list of ordered (r,z) points, which are exactly the (x,y) points from your drawing, including (0,0) and (0, z-max) at the ends to make it a closed volume. This surface between points will not be interpolated, but will consist of flat (conical) sections.

The computational effort, in particular the calculation of boundary crossings during tracking, scales with the number of control points. If the precise shape does not affect the outcome of your simulation, you make consider dropping some of the points between (2) and (17) to speed up the code.

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