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Idea Re: Tesselated solid overlap issue leaktest. 

Forum: Geometry
Re: Question Tesselated solid overlap issue leaktest. (David Takacs)
Date: 22 Mar, 2017
From: Michael H. Kelsey <Michael H. Kelsey>

On Tue, 07 Mar 2017 12:56:03 GMT, David Takacs wrote:
> We have a geometry in SolidWorks which we would like to import to
> geant4. The way we do it is the following: 1. We export the files from
> SolidWorks in a .stl format 2. Import them to blender, and export them
> as a .raw format. Raw format builds up our geometry using triangles. 3.
> After importing the raw files to geant4 as G4TesselatedSolid's we get
> overlap errors when running it. We will attach photos of the overlap
> error and pictures of where the overlap actually is.
> 
> Attachment:
> As you can see in the attached pictures we have 2 concentric tubes and since the circles are polygons they overlap where the circles wouldn't overlap.
>       http://hypernews.slac.stanford.edu/HyperNews/geant4/get/AUX/2017/03/07/04.43-41820-slacsidemid.png
>       http://hypernews.slac.stanford.edu/HyperNews/geant4/get/AUX/2017/03/07/04.43-15477-slacerror.png

You may need to tune your SolidWorks export to require a (much!) smaller position and angular error when generating the STL files. This will increase the number of polygon sides on the cylinders, making them better approximations.

You shouldn't necessarily need to go from STL to RAW format. There are some solutions available for going from STL directly into G4 (see Section 4.1.2.3, p. 109, of the App Guide), though none of them are perfect.

How complicated is your overall geometry? I had a similar issue on a project, and I ended up replacing some of the cylindrical components with hand-built Geant4 geometry objects (G4Tubs). It's annoying, I admit, but if you really have nested cylinders it may be necessary.

One question -- in your SolidWorks model, does it report any volume overlaps in the original model?

  -- Mike Kelsey

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1 Feedback: Re: Tesselated solid overlap issue leaktest.   (David Takacs - 28 Mar, 2017)
(_ None: Re: Tesselated solid overlap issue leaktest.   (Mike Kelsey - 28 Mar, 2017)
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