|Message: Problem with G4ExtrudedSolid||Not Logged In (login)|
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Hi everybody, I am trying to model a multi leaf collimator in a medical application and the G4ExtrudedSolid seems to be just the right solid for the individual leaves. However, for my geometry the class does not produce the solid that I would expect. I use the following polygon: // cross section of leaf in xy (polygon) std::vector<G4TwoVector> MLCLeaf_section; MLCLeaf_section.push_back( G4TwoVector(-2*mm, 1*mm) ); MLCLeaf_section.push_back( G4TwoVector(-2*mm, 25*mm) ); MLCLeaf_section.push_back( G4TwoVector( 1*mm, 25*mm) ); MLCLeaf_section.push_back( G4TwoVector( 1*mm, -1*mm) ); MLCLeaf_section.push_back( G4TwoVector( 2*mm, -1*mm) ); MLCLeaf_section.push_back( G4TwoVector( 2*mm, -25*mm) ); MLCLeaf_section.push_back( G4TwoVector(-1*mm, -25*mm) ); MLCLeaf_section.push_back( G4TwoVector(-1*mm, 1*mm) ); and would expect to get a point symmetric shape like this: http://web.physik.rwth-aachen.de/~lotze/geant4/crosssection.png However, what I get is http://web.physik.rwth-aachen.de/~lotze/geant4/vrml.jpg (the shape on the right, on the left there is an identically implemented G4ExtrudedSolid but using polygon data from the example in the application developers guide, which obviously works). On the right side of the collimator leaf the identation is visible in the wire frame, but the surface is somewhat larger and there are some non-perpendicular angles. First I thought it might be a visualisation problem, but RaytracerX gives me the same: http://web.physik.rwth-aachen.de/~lotze/geant4/g4RayTracer.viewer-0_0.jpeg (seen from the other side). I also tried changing the order of the points in the polygon but without success. Does anybody have an idea what I am doing wrong or what is going wrong otherwise? If you want to take a look at the code: http://web.physik.rwth-aachen.de/~lotze/geant4/ExtrudedSolidTest.tgz Thanks for your help! Sven Lotze
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