Resolve the TRD chamber by name when chamber assemblies have no volume id - #15873
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…e id This fixes the TRD initialisation abort under native Geant4 navigation (G4.navmode=kG4). - The VGM conversion collapses the chamber assemblies UT00-UT29, which then have no Geant4 volume id, and buildVolumeIdTables aborted with "TRD volume UT00 has no usable volume id". - In that case the chamber is read from the assembly name that CurrentVolOffName still reports. - TGeo and VecGeom keep the integer lookup; their TRD hits are bit-identical. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
bazinski
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Sep 30, 2026
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This fixes an abort at TRD initialisation when o2-sim runs with native Geant4 navigation (
G4.navmode=kG4), which serves as the independent reference when validating the TGeo and VecGeom navigation modes.The integer volume-id lookup introduced for the TRD hits used the ids of the chamber assemblies
UT00–UT29. The VGM conversion to Geant4 collapses assemblies, so they have no volume id and initialisation stopped withTRD volume UT00 has no usable volume id. In that case the chamber is now read from the assembly name, which geant4_vmc still reports. TGeo and VecGeom keep the integer lookup, and their TRD hits are bit-identical.With native Geant4, 500 pp events give the TGeo TRD hit count (ratio 1.001) and hit the same 521 chambers.
Assisted by Claude Code.