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  1. ROOT
  2. ROOT-8844

Loss of precision in gGeoManager Export

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    Details

    • Type: Bug
    • Status: Closed (View Workflow)
    • Priority: Medium
    • Resolution: Fixed
    • Affects Version/s: 6.10/00
    • Fix Version/s: 6.14/00
    • Component/s: Geometry
    • Labels:
      None
    • Environment:

      macOS clang8

      Description

      The numerical precision of values exported is significantly less than double precision. This limits the tracking precision and creates gaps/overlaps between volumes for imported geometries
      (seen when importing gdml in Geant4 for long thin geometries in FCC studies).

      Example (tube position - same for other geometries)
      18.067141635485662 "true" value printed to 17 digits to avoid any loss in precision
      18.0671416355 GDML export
      18.067142 C export
      1.806714e+01 XML export

      To avoid any loss in precision by geometry export I, propose that values are written to 17 digits
      ( by changing "%.12g" to "%.17g" in case of TGDMLWrite.cxx )

      Cheers, Helmut Burkhardt

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            Assignee:
            agheata Andrei Gheata
            Reporter:
            hbu Helmut Burkhardt
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