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Question Using Boolean Solids with Tessellated Solids 

Forum: Geometry
Date: 11 Aug, 2010
From: Daniel O'Brien <Daniel O'Brien>

Hi everyone,

I was wondering if anyone could help me. I'm attempted to generate a particular shape (a leaf from a multi-leaf collimator on a medical linac) which has a curved surface on one side and a flat jagged surface on the sides perpendicular to it.

The most straightforward way of doing this was to create the jagged surface with a G4TessellatedSolid and the curved surface with a G4Tubs and use G4IntersectionSolid to combine them into the correct shape.

This seemed to have the desired effect (although I cannot visualise the shape in OGLIX or HepRep, I determined if the shape was correct by writing a Geant4 simulation that essentially took an x-ray image of the shape), however during the course of the run I get the following warning repeatedly:

    Solid name       = MLC Leaf Steps
    Geometry Type    = G4TessellatedSolid
    Number of facets = 14
    Position:

    p.x() = -13.05233040123778 mm
    p.y() = 55.5358564711038 mm
    p.z() = -3.5 mm

    *** G4Exception : UnknownInsideOutside
          issued by : G4TessellatedSolid::Inside()
    Cannot determine whether point is inside or outside volume!
    *** This is just a warning message.

Does anyone know why this is happening? It happens if I use the G4UnionSolid aswell. I'm completely confident that I have defined both components (the G4Tubs and the G4TessellatedSolid) correctly and using them individually produces no warnings or errors whatsoever.

Perhaps more importantly is, should I be concerned about this? It says it's just a warning and the photon transport through the solid appears to be behaving as expected (as evidenced by my simple x-ray imaging program).

I'd appreciate any help you can provide.

Thanks in advance,

Daniel

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1 None: Re: Using Boolean Solids with Tessellated Solids   (John Allison - 11 Aug, 2010)
(_ None: Re: Using Boolean Solids with Tessellated Solids   (Daniel O'Brien - 16 Aug, 2010)
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