DD4hep-based simulation plugins, front-end, and related utilities
npsim (formerly NPDet) provides DD4hep/DDG4 simulation plugins (e.g. EIC-specific particle handling and interaction-vertex smearing) and the npsim front-end script for running Geant4 simulations against an EIC detector description such as epic. Built here against hep-forge's own dd4hep/root -- part of hep-forge's EIC Phase 1 simulation-chain build-out (geant -> g4hepem -> dd4hep -> epic -> npsim, plus acts).
