1. A CAD/Geant4 Front-end Interface
Fan Lei
Space Department, Defence Evaluation & Research Agency,
Farnborough, UK
Rodolfo Gurriaran
Department of Physics & Astronomy, University of Southampton
Southampton, UK
(Some images and data in this presentation courtesy of PDES Inc.)

2. Introduction
A front-end user interface to allow space engineers to import CAD model into the Geant4 based space radiation shielding calculation tools.
The development process has been divided into two phases
Phase I: Investigate compliance of major CAD tools with STEP protocol or future trends in this direction. Define a set of user requirements for a CAD front-end interface for the space radiation effects community. Assess their possible application as a front-end for geometry/material definition for G4 based tools.
Phase II: The design and development of the front-end interface. The final esign is a combination of a CAD system and a Material Generation & Association tool. The later is adapted from GGE.
The work has been carried out by University of Southampton

5. Some Comments AP203 ISO standard since 1994
The compliance of CAD systems is evolving fast
Many CAD system claim to be compliant, but in reality only partial
some “old” STEP files forget the “management” information (class1)
AutoCAD R15 partially implement class1, not class 3 nor 5.
CATIA the first to be certified conformant with the STEP international standard (AP203)
PDES generated a “Recommended Practices for AP203” in 1998:
class 1 is required.
For this work, class 1 “management information” must be present (“PRODUCT” field)

6. Evaluation of CAD status
CAD Product: Suitability for G4 based application:
ProEngineer (Parametric) yes
Euclid (Matra Datavision) yes (with translator)
Catia (IBM Dassault) yes
MicroStation (Bentley) translator released ?
AutoCAD (AutoDesk) yes (R )
I-deas (SDRC) yes
It is not possible to use a CAD system to define and manage the material information as required in Geant4

7. G4 STEP reader Based on a free tool from NIST
Instantiate geometry in STEP file as G4LogicalVolumes
limitations :
accesses only geometry information, does not access the “management” information, i.e. the class 1 data.
How to associate material to each volume ?
To enhance the reader to read the class 1 information
temporary solution: use the sequential coincidence between volumes in step file and mga file.

8. Front-end User Interface
The Interface consists of
An off-the-shelf CAD system: for geometry modeling. The design is outputted in a STEP file.
The Material Generation & Association (MGA) tool: allow user to define the materials and associate them with volumes in the STEP file. The results are outputted in a MGA file.
The STEP and MGA files will be used to define the geometry in a G4 application automatically.

9. G4 Application Using STEP & MGA Files
Requirement on STEP file format:
AP 203
Volumes are named
A description of material is
desired.
MGA file format:
See the document: UoS-rep-05

10. MGA Design of the MGA tool is based largely on GGE: the G4 geometry
editor.

11. Future Work Enhance the G4 STEP reader: compliance to AP203 class 1.
More tests with variuous types of STEP files from ESA, created by different CAD tools.
Integration of MGA/GGE?
Commit the proper G4mgareader to the G4 repository.
Documentation.

12. Relevant Documents G3 and CAD systems (UoS-rep-01)
GEANT4 and CAD systems (UoS-rep-02)
Following documents can be found in DERA web pages:
URD CAD-Tool Front-End to GEANT4/SPARSET (UoS-rep-03)
Discussion Document on the General Design of the CAD Front End Tool (UoS-rep-04)
Development of GGE to perform materials and visualisation attribute definition in the CAD tool front end (UoS-rep-05)
SSD CAD Front End Tool for GEANT4/SPARSET (UoS-rep-06)