1. GDML “Geometry Description Markup Language” by Daniele Francesco Kruse University of Rome “Tor Vergata” European Organization for Nuclear Research

2. Outline Why is GDML so useful? What am I going to talk about? We need a standard detector geometry description language that we can use in our applications MotivationSummary of the presentation 1)What is GDML? 2)What is my job here at CERN? 3)Achievement 1: MODULARITY 4)Achievement 2: LOOPS & MATRICES 5)Achievement 3: IMPORTING CAD FILES

3. GDML A means to share Geometry Information among applications POWERFUL -Able to describe geometry in a clear and readable way -It’s easy to understand / edit / update GDML files -Flow-control and modularity INDEPENDENT -Architecture independent -Operating system independent -MOST IMPORTANT: Application independent EXTENSIBLE -Defined by XML Schema files (.xsd) -Possibility to extend it with new tags and structure changes -Easily interfaced with future applications  common I/O core

4. The Interface The Binding with User Applications Input GDML File The Interface -Common I/O core (multiple apps) -Specialized interface (1 per app) The Application -Applications that use Geometry Info -Geant4, ROOT, etc... Output GDML File

5. GDML A simple GDML document... Define Material s Define Solids Define Structure (you can then put this volume in a mother volume)

6. My job@CERN The Interface with ROOT and Geant4 The Geant4 – GDML Binding - Support for the exportation of new solids (tet, tess, etc...) - Multiple GDML files support (input & output) - Support for variable name scope - Support for the tag The ROOT – GDML Binding - Support for new complex solids (Xtru, Arb8, etc...) - I/O System refinement

7. Modularity Divide et Impera... BEFORE Atlas geometry (Tens of Millions of physical volumes) would be described using only 1 GDML file! (Tens of MB) -Huge -Very complicated ATLAS MODULARISATION Big GDML file Main file Mod. 1 Mod. 1.1 Mod. 1.2 Mod. 2 Mod. 2.2Mod. 2.1 2.1.12.1.22.1.3 AFTER Split the geometry into small modules ADVANTAGES: 1) Readability 2) Indipendency 3) Reusability Some Example Code Instead of writing: You should write:

8. Loop & Matrix Avoiding repetitions and using tables of values Suppose you want to create the following......normally you would have to write all this GDML code:......but using the & tags the GDML code will be much shorter: <matrix name=“m” coldim=“5” values=“0 2 3.5 3.9 4.15 5 4 3.2 2.56 2.048” />...

9. STEPGDML The GDML - STEP Binding ST - Viewer An interactive tool for viewing 3D CAD information STEP files ST – Viewer uses an internal file format (.geom &.tree) to store geometry info STEPGDML Library functions created to convert STEP files into GDML files GDML Output File Equivalent to the original STEP file Contains only tessellated solids Does not contain material info

10. Conclusions what was this all about? what have I done for CERN? GDML is more flexible now because you can: a) use many new kinds of solids in your geometry description b) split huge geometry info into smaller GDML modular files c) use the flow-control tag to avoid tedious repetitions of solids and volumes d) use the tag to store values in a table format e) import geometries constructed in classical CAD tools

11. That’s All Folks! Many Thanks to: Witold Pokorski (my supervisor) for his help and understanding during these 3 months My good Friends at CERN for the great times we had together and to All of You for your kind Attention...