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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Hi Ashish,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Thanks for replying.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Let me explain my problem again. I have attached 3 pictures below. First, shows a Tetrahedral mesh of square duct. So, all surface elements are Triangle. Second,
shows normal vectors computed using cross product if Triangle vertices are saved in clockwise sense (in the picture). Third, shows normal vector computed if Triangle vertices are saved in anti-clockwise sense. So, second picture gives me outward normal which
I need.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">I found that all Triangles do not give me outward normals if I assume clockwise sense (in following picture). So, I wanted to know if GMSH has some other way
to provide me outward normal for each surface Triangle. <o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><img width="314" height="303" id="Picture_x0020_1" src="cid:image002.jpg@01CD2923.5C91B6E0"></span><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"> <img width="507" height="322" id="Picture_x0020_2" src="cid:image006.jpg@01CD2923.5C91B6E0"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Thanks,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Ashish<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
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<p class="MsoNormal"><b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">From:</span></b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif""> Ashish Garg [mailto:ashish.garg.iisc@gmail.com]
<br>
<b>Sent:</b> Wednesday, May 02, 2012 1:09 PM<br>
<b>To:</b> Negi, Ashish<br>
<b>Cc:</b> gmsh@geuz.org<br>
<b>Subject:</b> Re: [Gmsh] outward normal of surface triangles<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal" style="margin-bottom:12.0pt">Hi Ashish<br>
<br>
give the condition that the cross product should be greater than zero. I guess it will resolve the problem.<br>
<br>
Ashish Garg<o:p></o:p></p>
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<p class="MsoNormal">On Wed, May 2, 2012 at 12:38 PM, Negi, Ashish <<a href="mailto:ashish.negi@honeywell.com" target="_blank">ashish.negi@honeywell.com</a>> wrote:<o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">Hello Everyone,<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">I’ve been using GMSH library to open Nastran BDF file and extract mesh data for my software. I generally load a mesh consisting of only Tetrahedra. Hence, surface of model have
only Triangle elements. <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">I want to find outward normal at each Triangle. I get coordinates of each Triangle and then take cross product to get normal to the element. But, I’m not sure if it will always
be outward. Can someone suggest a solution to this problem?<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">Thanks,<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">Ashish<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
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