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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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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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