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None Tesselated GDML-structures and transformations (overlaps) 

Forum: Persistency
Date: 28 May, 2010
From: Jonning Kennethson <Jonning Kennethson>

Hello, I've used fastrad to convert some cad->step files to GDML.

It works almost smoothly, producing a huge file that will with a a few fixes and minute overlap-corrections from the direct output of fastrad give me a beautiful tesselated structure into G4.

But here is what baffles me: if i apply a affine transformation, such as a rotation, to all my physical volumes, I would from basic linear algebra assume there will be no overlaps if there weren't any before.

But adding in any sort of little rotation will give me a bunch of huge overlaps.

A transformation seemed to go fine, but very little else.

My first thought was there is some bug in the gdml parser. But I wrote some python that parses through the gdml-file and applies the same transformation directly to the coordinates. And the same happens with this as well.

Anyone got any clue where I should look for the problem?

Also, the documentation does not even say which point it exactly is that a tesselated volumes "position" is.

Any input greatly appreciated.

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