Does TGeoManager::CheckOverlaps work in v4.04?

Dear experts,

I was trying to test the useful function TGeoManager::CheckOverlaps (or TGeoVolume::CheckOverlaps). I’m using ROOT version 4.04 – that is what our experiment group uses now. I made two Boxes, and deliberately put them in one TGeoVolume so that they are partially overlapped. Then I called TGeoManager::CheckOverlaps (as well as TGeoVolume::CheckOverlaps), but it returned with “0 overlaps”. Does it work in ROOT v4.04? Isn’t it designed to catch any mistakes in making a (e.g. detector) geometry system?

Thanks a lot,

Hi Fu,

The algorithm used for checking verifies if any of the mesh vertices of one shape is inside (or not) the other. If this is the case, it computes the safe distance from that vertex to the other shape surface. This algorithm fails to find the true overlap value if the overlap is such that the vertices of one candidate are exactly on the surface of the other. This is probably your case for 2 boxes.