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Question Re: cylinder overlapping : similar problem! 

Keywords: Overlapping G4Tubs sections
Forum: Geometry
Re: Question cylinder overlapping (cognet marie-anne)
Date: 30 Nov, 2005
From: Zach Hartwig <>

Hi all,
   I am currently having very similar problem to Marie-Anne.  For example
I am attempting to build a cylinder with inner radius 5 m, outer radius 
7.25 m, height 0.2 m; however, I would like to build it out of 12, 
30-degree G4Tubs sections placed immediately next to each other along 
an azimuthal line to construct the full 360-degree cylinder.  I have 
tried two different methods.  

1) Build the 12 G4Tubs sections by passing 0-degree and 30-degree in the
constructor for Sphi and Dphi, and then rotating the section by 30, 60, 
90 degrees etc to place the object appropriately

2) Build the 12 G4Tubs sections by passing (0*degree,30*degree) for 
section 1, (30*degree,60*degree), for section 2, etc so that I auto-
matically build the sections into place.

Both the GEANT4 "geometry/test/cylinder_test" method and DAVID 
visualization report that ALL 12 sections overlap, despite the fact that
one G4Tubs section should end *exactly* where another begins.  Also, 
GEANT4 reports all sorts of navigation errors during run-time.

Changing the Dsphi argument from "30*degree" to "29.99*degree" causes 
only 2 sections to overlap using DAVID.  Changing to "29*degree" causes
4 sections to overlap even though they do not touch any other objects!! 
I do not understand why.

Can anyone provide any insight into this apparently basic geometry
problem?  I could post source code if needed.

Thanks very much!

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1 Note: Re: cylinder overlapping   (Adrian Vogel - 05 Dec, 2005)
(_ Agree: Re: cylinder overlapping   (Zach Hartwig - 05 Dec, 2005)
(_ More: Re: cylinder overlapping   (Vladimir Grichine - 07 Dec, 2005)
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