ROOT Geometry PackageL 1

The New ROOTGeometry Package

ACAT2002Moscow 24 June

René Brun, Andrei & Mihaela Gheata

CERN

ACAT2002 ROOT Geometry Package 2

Simulation tools

Geant3created in 1981

Still used bythe majority

of experiments

FlukaState of the artfor hadronics

and neutron physics

Geant4A huge investment

Slow penetrationin experiments

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Detector Geometry (way 1)

Geant4geometry

Reconstructionprogram

Simulationprogram

Geant4-based

XMLfiles

C++classes

MySQL

Visualisation

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The Virtual MonteCarlo

DAQ

Online

TVirtualMC

Geant3

Fluka

Geant4Kinematics Geometry

Hits, Digits

This strategy facilitates

migration or comparisons

with a common input

and a common output

Geant3.tar.gz includesan upgraded Geant3

with a C++ interface

Geant4_mc.tar.gz includesthe TVirtualMC <-->Geant4

interface classes

For exampleAliRootin Alice

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Virtual MC example (with G3)

{ // Load basic libraries gSystem->Load("libPhysics"); gSystem->Load("libMC"); gSystem->Load("$(MCINSTALL)/lib/Linux-g++/libexample01");

// Load Geant3 libraries // … skipped

// MC application Ex01MCApplication* appl = new Ex01MCApplication("Example01", "The example01 MC

application");

appl->InitMC("g3Config.C"); appl->RunMC(1);

} void Config() g3Config.C{ cout << "Create geant3" << endl; new TGeant3("C++ Interface to Geant3");}

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Virtual MC example (with G4)

{ // Load basic libraries gSystem->Load("libPhysics"); gSystem->Load("libMC"); gSystem->Load("$(MCINSTALL)/lib/Linux-g++/libexample01");

// Load Geant4 libraries // … skipped

// MC application Ex01MCApplication* appl = new Ex01MCApplication("Example01", "The example01 MC

application");

appl->InitMC("g4Config.C"); appl->RunMC(1);}

void Config() { g4Config.C

// RunConfiguration for Geant4 TG4RunConfiguration* runConfiguration = new TG4RunConfiguration();

// TGeant4 new TGeant4("TGeant4", "The Geant4 Monte Carlo", runConfiguration);}

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Detector Geometry (way 2)

Geometrypackage

Reconstructionprogram

Simulationprogram

Geant3-basedGeant4-basedFluka-based

C++classes

MySQL

Visualisation

Modelling

Visualisation

Interactivity

Where am I?

Distance to boundary

Closest boundary

Persistency

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The new ROOT Geometry package

Was the request Nr 1 at ROOT FNAL workshop in June 2001

The package is being developed in collaboration with Alice (Andrei & Mihaela Gheata)

Alpha release in July faster than Geant3 Import from Geant3 (eg 4 LHC detectors) Interfaces to Geant3,4, Fluka in view Demos on request

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The TGeo classes in htmlhttp://pcbrun.cern.ch/geo/ClassIndex.html

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TGeoManager

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TGeoShape

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TGeoVolume

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TGeoNode

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Example

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Automatic conversion from Geant3

Zebra memoryData structure

JVOLUMJMATE,etc

Geant > RZ/File 21 mygeom.geom on

Zebra RZmygeom.geom

g2root mygeom.geom mygeom.C

void gexam1(){TGeoMaterial *mat;TGeoMixture *mix;

TGeoManager *gexam1 = new TGeoManager("gexam1","gexam1.C");

//-----------List of Materials and Mixtures--------------

mat = new TGeoMaterial("mat9","ALUMINIUM",26.98,13,2.7);mix = new TGeoMixture("mix10","IRON(COMPOUND)",3); mix->DefineElement(0,55.847,26,0.703964); mix->DefineElement(1,58.71,28,0.9900000E-01); mix->DefineElement(2,51.998,24,0.197);mat = new TGeoMaterial("mat11","COPPER",63.54,29,8.96);

Root > .x mygeom.C Mygeom.c

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Example : gexam1

void gexam1() {TGeoMaterial *mat;TGeoMixture *mix;

TGeoManager *gexam1;gexam1 = new TGeoManager("gexam1","gexam1.C");

//-----------List of Materials and Mixtures--------------

mat = new TGeoMaterial("mat9","ALUMINIUM",26.98,13,2.7);mix = new TGeoMixture("mix10","IRON(COMPOUND)",3); mix->DefineElement(0,55.847,26,0.703964); mix->DefineElement(1,58.71,28,0.9900000E-01); mix->DefineElement(2,51.998,24,0.197);mat = new TGeoMaterial("mat11","COPPER",63.54,29,8.96);mat = new TGeoMaterial("mat13","LEAD",207.19,82,11.35);mat = new TGeoMaterial("mat14","URANIUM",238.03,92,18.95);mat = new TGeoMaterial("mat15","AIR",14.61,7.3,0.1205E-02);mat = new TGeoMaterial("mat16","VACUUM",0,0,0);mix = new TGeoMixture("mix21","BGO(COMPOUND)",3); mix->DefineElement(0,208.98,83,0.6710563); mix->DefineElement(1,72.59,32,0.1748205); mix->DefineElement(2,15.999,8,0.1541233);mix = new TGeoMixture("mix22","LEAD GLASS",6); mix->DefineElement(0,207.19,82,0.65994); mix->DefineElement(1,39.102,19,0.7990000E-02); mix->DefineElement(2,28.088,14,0.126676); mix->DefineElement(3,22.99,11,0.4007300E-02); mix->DefineElement(4,15.999,8,0.199281); mix->DefineElement(5,74.922,33,0.2004850E-02);

//-----------List of Volumes--------------

TGeoVolume *ECAL ;ECAL = gexam1-> MakeTube("ECAL","mat15",0,5.898013,12.35774);LEAK = gexam1->MakeTube("LEAK","mat15",0,5.898013,0.5617155);LATR = gexam1->MakeTube("LATR","mat15",5.617156,5.813,11.23);BLOC = gexam1->MakeTube("BLOC","mix21",0,5.617156,11.23431);

//-----------List of Nodes--------------

gexam1->SetTopVolume(ECAL); ECAL->AddNode(LEAK,1,new TGeoTranslation(0,0,-11.79603)); ECAL->AddNode(LEAK,2,new TGeoTranslation(0,0,11.79603)); ECAL->AddNode(LATR,1,gGeoIdentity); ECAL->AddNode(BLOC,1,gGeoIdentity); TGeoVolume *RTUB = BLOC->Divide("RTUB",1,20,0,0.2808578); TGeoVolume *RING = RTUB->Divide("RING",3,20,-11.31,1.131); gexam1->CloseGeometry();}

gexam1.C codegenerated automatically

by g2root

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Brahms2649 nodes

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CMS

1.3 million nodes

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Atlas 29 million nodes

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Atlas

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Atlas

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Alice

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Alice 3 million nodes

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TGeo performance vs Geant3

Number gtmedi Root Geant3/ gtmedi Root Geant3/ nodes physics physics Root random random RootGexam1 425 3.08 1.84 1.67 6.60 4.39 1.50Gexam3 86 2.87 2.15 1.33 3.47 2.50 1.38Gexam4 12781 2.51 2.20 1.14 12.09 11.18 1.08Brahms 2649 5.82 3.04 1.91 4.17 1.93 2.16Tesla 15370 6.56 5.58 1.17 12.95 7.15 1.81CDF 24422 14.81 4.31 3.43 20.94 5.85 3.57Minos_near 30988 30.93 20.99 1.47 21.57 13.70 1.57BTeVEcal 52 1.57 1.08 1.45 1.78 0.73 2.43BTeV 295310 45.27 25.88 1.75 197.06 26.83 7.34CMSEcal 251713 5.60 1.81 3.09 5.69 1.74 3.27CMS 1166310 33.57 8.76 3.83 39.09 24.98 1.56LHCb 1533488 7.98 6.75 1.18 12.58 2.89 4.35Alice 3080198 11.50 8.63 1.33 11.45 7.28 1.57Atlas 29046966 8.90 9.94 0.89 32.48 23.39 1.38

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BteV

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Validation Procedure

Use one million points generated by Geant3.

Compare G3 path vs TGeo found path (pictures for a CDF event)

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Validation Procedure Using points generated by Geant3 applications

grecord.f --> mygeom.geom, mygeom.hbook

Play-back these points in Geant3 using only the Geant3 geometry package. Compute g3path, snext, safety in myresults.hbook

h2root myresults.hbook myresults.root Same operation with TGeo classes. Compare

g3path with tgeopath, same for snext, safety Some discrepancies with Geant3 (see next)

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Validation ProcedureDifferences Geant3 TGeo

Due to precision problems in Geant3, points recorded at the volume boundaries may be found on the other side by TGeo.

When volumes declared MANY in Geant3 overlap and have sub-volumes also MANY, Geant3 is not always reporting the right answer. In general it does not matter, sometimes it does.

In this exercise, we also found original errors in the detector description, eg wrong parameters.

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Status of the implementation - test of gtnext

• Visualization - best tool for checking the algorithms

• The "width" of the boundaries due to floating point limitations was determined for some shapes

• This diffusion effect is crucial for fixing stepping actions in order to trigger expected inside/ouside response of the modeler

• The diffusion was defined as the distance between extrapolated point from step and closest point that changes this in/out response.

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Status of the implementation

Geant3 geometries - almost fully mapped (still not supporting multiple positioning for volumes having shapes with negative parameters which then are divided - quite seldom topology)

"Where am I ?" - fully implemented Tested on a dozen of geometries, including all 4 LHC

experiments Performance w.r.t GEANT3 - OK. The average gain factor

~1.5-2.0 , increasing for flat-like geometries Consistency vs. GEANT3 response reasonable : still few

% differences, but fully understood Still scope for increasing speed, specially for cylindrical

symmetries, where the current voxelization algorithm is not efficient enough.

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Status of the implementation - gtnext

"Which is the next crossed boundary ?" - about 80% implemented, still a couple of weeks to work on it.

Algorithms per shape improved w.r.t G3 for some shapes New functionalities added : normals to surfaces at

crossing points, accurate distance to closest node, direction vector to closest point

Features for stepping added : flags for entering and exiting

SHAPE BOX PARA TUBE TUBS CONE CONS SPHEREFROM INFROM OUT

SHAPE TRD1 TRD2 TRAP GTRA CTUB PCON PGONFROM INFROM OUT

ALGO. GLOBAL VOXELS DIVISIONS"MANY"

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Summary

The new Geometry Package looks very promising.

We have been able to model all existing large detectors.

Performance is better than Geant3. We are planing to interface it via

TVirtualMC to Geant3, Geant4 and Fluka. Alpha release with ROOT version 3.03/07