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Current methods of geometry description Requirements Proposal Status. Generic Geometry in XML. Simulation Geometry Now.
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Current methods of geometry description Requirements Proposal Status Generic Geometry in XML Generic Geometry J. Bogart
Simulation Geometry Now • Glastsim (simulation using gismo) reads geometry parameters (dimensions, materials, etc.) from instrument.xml. Constants are separated from code;assumptions about structure, relation between volumes are not. • Nothing in instrument.xml addresses assignment of ids to readout volumes; this knowledge is embedded in Glastsim. • Geant4 balloon simulation currently has hard-coded geometry. Generic Geometry J. Bogart
Event Data Clients Now • The association between readout id and detector location is made available to Recon by Glastsim dumping detector objects to a 40k line XML file glast.prs • Minor detector design changes can be handled by writing a new version of glast.prs from Glastsim. • Changes in the information Recon needs (e.g., to interpret energy-accounting data) require mods to Glastsim and the glast.prs format as well as to Recon. Generic Geometry J. Bogart
Requirements • Support several configurations (e.g., flight instrument, balloon instrument), and variants. Get geometry assumptions, parameters out of the code. • Recon and other data clients need part of geometry info known to simulator. At least must reconstitute the association between readout ids and location. • Geometry description must be accessible to humansand to multiple programs (Geant4 simulation, gismo?, Recon,...). Generic Geometry J. Bogart
Geometry Information Flow Now To come parameters volumes, relations, id specification Simulator ids, nesting sensitivedetectors dump Simulator Recon Recon Generic Geometry J. Bogart
Proposal Use variant of the XML language being developed by the ATLAS experiment. Encodes structural information (relationships between volumes) as well as constants. Handles association of ids with volumes Natural mapping to Geant4 geometry description Generic parameter blocks if we need them Generic Geometry J. Bogart
How It Works • Describe logical (platonic) fundamental volumes, such as a diode, in terms of shape, dimensions, material. May make stacks or arbitrary composite logical volumes. • Make a physical copy of a logical volume by positioning it inside another volume. • Can associate an identifier with any positioned volume. Can associate an arbitrary parameter block with any logical volume. • Part of a tower description uses most of this. Generic Geometry J. Bogart
Status • Define description language (GGDD) About done; may need math expression addendum. • Use it. Flight instrument description is mostly done.Balloon would be straightforward. • Geant4 interface utilities. Not yet begun.But GDDD is G4-like. And ATLAS has a stand-alone tool (G4Builder) which may be cannibalized. • Gismo interface utilities.Not yet begun.Do we want it? Generic Geometry J. Bogart
Status (cont’d) • Use by Recon, etc. Not done and not obvious what the best approach is (use simulation input file or something derived from it?) • Schedule issues • This work is not needed for the balloon, but the flexibility it offers would be welcome as soon as possible • Total time is measured in months • Work naturally splits into several separate projects Generic Geometry J. Bogart