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| 3 | <!-- [History] --> |
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| 4 | <!-- Converted to DocBook: Katsuya Amako, Aug-2006 --> |
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| 5 | <!-- Changed by: Gabriele Cosmo, 18-Apr-2005 --> |
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| 7 | <!-- ******************************************************** --> |
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| 9 | |
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| 10 | <!-- ******************* Section (Level#2) ****************** --> |
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| 11 | <sect2 id="sect.Geom.Intro"> |
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| 12 | <title> |
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| 13 | Introduction |
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| 14 | </title> |
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| 15 | |
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| 16 | <para> |
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| 17 | The detector definition requires the representation of its |
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| 18 | geometrical elements, their materials and electronics properties, |
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| 19 | together with visualization attributes and user defined properties. |
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| 20 | The geometrical representation of detector elements focuses on the |
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| 21 | definition of solid models and their spatial position, as well as |
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| 22 | their logical relations to one another, such as in the case of |
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| 23 | containment. |
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| 24 | </para> |
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| 25 | |
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| 26 | <para> |
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| 27 | Geant4 uses the concept of "Logical Volume" to manage the |
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| 28 | representation of detector element properties. The concept of |
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| 29 | "Physical Volume" is used to manage the representation of the |
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| 30 | spatial positioning of detector elements and their logical |
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| 31 | relations. The concept of "Solid" is used to manage the |
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| 32 | representation of the detector element solid modeling. |
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| 33 | Volumes and solids must be dynamically allocated in the user |
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| 34 | program; objects allocated are automatically registered in |
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| 35 | dedicated stores which also take care to free the memory at |
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| 36 | the end of a job. |
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| 37 | </para> |
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| 38 | |
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| 39 | <para> |
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| 40 | The Geant4 solid modeler is STEP compliant. STEP is the ISO |
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| 41 | standard defining the protocol for exchanging geometrical data |
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| 42 | between CAD systems. This is achieved by standardizing the |
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| 43 | representation of solid models via the EXPRESS object definition |
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| 44 | language, which is part of the STEP ISO standard. |
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| 45 | </para> |
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| 46 | |
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| 47 | </sect2> |
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