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      <title>Auto normal generation</title>
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      <div class="title_topic3" id="xps10_pagetitle">Auto normal generation</div>
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               <p class="para_td"><a class="links" href="javascript:void(0)" onclick="top.openFile('rapidprototyping/introduction.html');return(false);">Overview</a></p>
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               <p class="para_td"><a class="links" href="javascript:void(0)" onclick="top.openFile('rapidprototyping/pro_prototyping.html');return(false);">How To</a></p>
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               <p class="para_td">Options</p>
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               <p class="para_td"><a class="links" href="javascript:void(0)" onclick="top.openFile('rapidprototyping/error_mess.html');return(false);">Related Topics</a></p>
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      </table><br><p class="para_topic">The system uses surface normals to calculate the normals for the triangulation processing. If you know that a surface has a correctly oriented normal, this option allows you to use that normal to determine the normals for all other connected surfaces you want to process. You select a surface as the base surface and determine the correct normal for that surface. The system then determines and stores in the database the normals for any surfaces connected, directly or indirectly, to this base surface. This option switches between on and off. The default is on.</p>
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                  <p class="para_note_body"><b class="uiTerm">Auto Normal Generation</b> does not affect the processing of solids.
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      <div class="title_division">ON</div>
      <p class="para_division">If you set <b class="uiTerm">Auto Normal Generation</b> to on, later on the system will prompt you to select the base surface and displays the normal for that surface. The system then allows you to either reverse the direction for that normal to orient it correctly (by selecting Yes), or to accept the normal as displayed (by selecting <b class="uiTerm">No</b>). <b class="uiTerm">Re&ndash;display Normal</b> allows you to re&ndash;display the normal as currently set. Select <b class="uiTerm">Back</b> to return to the <b class="uiTerm">Class Selection</b> dialog box. This allows you to continue to select a surface until you find one with a desirable normal. Once the normal is set correctly, select <b class="uiTerm">OK</b>. The system then generates and stores the normals for all selected surfaces by virtue of adjacencies using this correct normal. After running the <b class="uiTerm">Auto Normal Generation</b> option, the system correctly sets all normals in the database.
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      <p class="para_division">Choose <b class="uiTerm">Refresh</b> to remove the displayed normals.
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      <p class="para_division">The system does not prompt you with these <b class="uiTerm">Auto Normal Generation</b> menus immediately after setting the option on from the main <b class="uiTerm">Rapid Prototyping</b> menu. These menus will automatically display after you use the <b class="uiTerm">Class Selection</b> dialog box to indicate which surfaces you want to process.
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                  <p class="para_note_body"><b class="uiTerm">Auto Normal Generation</b> will only work on a single body of surfaces (a group of surfaces that are all attached to each other). If you select a second body of surfaces, the known normal is not attached to one of the bodies by the necessary adjacencies. Therefore, the system cannot automatically calculate the normals for this second set of surfaces and displays an error message.
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      <div class="title_division">Off</div>
      <p class="para_division">When <b class="uiTerm">Auto Normal Generation</b> is turned off, the system assumes the existing normals to be correct and uses them to determine the normals of the triangles created during surface processing.
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            <td valign="top" align="left"><img align="left" src="../graphics/warning.gif" alt="Warning" title="Warning"></td>
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                  <p class="para_warning_body"> In general, turning <b class="uiTerm">Auto Normal Generation</b> to off is not a safe thing to do. Turn the option off only if you have some specific reason for manually setting the normals.
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