What could root geometry offer ?

1. Andrei Gheata, LC Software Workshop CERN 28-29 May 2009 What could root geometry offer ?

2. A full-fledged geometry modeler Available in ROOT since 2001 – initiative of ALICE offline and ROOT teams The development mainly motivated by the need of a tool to unify the geometry description in relation with simulation transport engines, but not only. First presented at CHEP 2003 - Some of the bonuses were foreseen at the time …

3. Features • A CSG hierarchical model based on an extended set of solid body primitives (shapes) • 20 shape types supportingBooleanoperations & scaling • Navigation functionalityextensivelytuned for performance and reliability • Severalbuilt-in features to ease-up detector geometrydefinition (divisions, assemblies, geometrybuilder GUI) • Full navigation functionalitybenchmarked and optimized for a big (~30) set of geometriescomingfrom G3 • Integrated in Virtual Monte Carlo framework , implemented for mostpopular transportation engines (GEANT3, GEANT4 and FLUKA) via navigation interfaces • Parallel navigation available with minimal changes (already proved to work) – see CHEP’09 contribution #460 • API available for otherpotentialcustomers (reconstruction)

4. Otherfeatures • Dynamic activation of geometrydetails in navigation • One does not need 2 geometryrepresentations for coarse or detailedgeometry • Native support for dynamicmisalignment • Directlyused in simulation and reconstruction • High-performance geometrycheckingtools • Overlap checker, raytracing utilities • Built-in support for geometry rendering • Hi-quality OpenGL visualization, client for event displays (see talk of MatevzTadel) • Ray tracing for high-definition images • ROOT I/O (fast) + import/export for other formats • GDML reader/writer • Export as C++ code • Radionuclide support (elements composing materials and mixtures) • Evolution in time according Bateman equation • Complete GUI library for geometry editing

5. ROOT geometry and simulation • TGeo can act as navigator for G3, G4 and FLUKA via VMC framework • Navigation fully validated against native geometries – reported at CHEP • Ongoing physics comparisons and fine tunes (G4 physics lists) in ALICE • In production in ALICE • Used by many other experiments

6. ROOT geometry and simulation • TGeo can act as navigator for G3, G4 and FLUKA via VMC framework • Navigation fully validated against native geometries – reported at CHEP • Ongoing physics comparisons and fine tunes (G4 physics lists) in ALICE

7. ROOT geometry and reconstruction • Tracking is using the full geometry to compute material budget-related corrections • ALICE has 4.3 Mio volumes in the detailed geometry • Alignment data is loaded on top of the ideal geometry and used directly • To apply corrections at the level of digits (position) • As input by alignment procedures that produce corrections to alignment objects

8. Visualization & Event display • Native OGL rendering • Supporting clipping, transparency, projections, … • Very good interactivity even for large level of detail • Used as component by EVE (see talk of Matevz) • Very powerful and versatile event display

9. Visualization & Event display

10. Instead of conclusions • Geometry is obviously something needed by several HEP SW components • The ROOT geometry package provides the functionality, API and interfaces required by most of them • Embedding big efforts for tuning and flawless quality, the tool is in production as core component in ALICE software • Adopted also as geometry baseline by other experiments