<div dir="ltr"><div><div><div>Surprisingly I have not been able to reproduce the issue with ParaView 5.2rc2/OpenGL2.<br></div>For the Slice filter, the "Triangulate the slice" option is turned ON by default.<br></div>Then ParaView polygonal data representation has a "Triangulate" advanced option that is turned OFF by default but you could need if data is not triangulated.<br><br></div>J.<br></div><div class="gmail_extra"><br clear="all"><div><div class="gmail_signature" data-smartmail="gmail_signature"><div dir="ltr"><div><div dir="ltr"><div><div dir="ltr"><div><div dir="ltr"><b>Joachim Pouderoux</b><font size="2">, <font size="1">PhD</font></font><br><blockquote style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><font size="1"><i>Technical Expert - Scientific Computing Team</i></font><br><b><font size="1"><a href="http://www.kitware.fr" target="_blank">Kitware SAS</a></font></b><br></blockquote>
</div></div></div></div></div></div></div></div></div>
<br><div class="gmail_quote">2016-10-26 9:23 GMT-04:00 Ken Martin <span dir="ltr"><<a href="mailto:ken.martin@kitware.com" target="_blank">ken.martin@kitware.com</a>></span>:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr">Basically it is OpenGL, in that OpenGL doesn't automatically tessellate concave polygons. Making VTK always examine every polygon to determine if it is  concave would be a performance hit for everyone, so we leave it up to developers to use a triangle filter if they need it. <div><br></div><div>Thanks</div><span class="HOEnZb"><font color="#888888"><div>Ken</div></font></span></div><div class="HOEnZb"><div class="h5"><div class="gmail_extra"><br><div class="gmail_quote">On Tue, Oct 18, 2016 at 9:11 AM, Stefan Melber <span dir="ltr"><<a href="mailto:Stefan.Melber@dlr.de" target="_blank">Stefan.Melber@dlr.de</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
  
    
  
  <div bgcolor="#FFFFFF" text="#000000">
    <div class="m_-7708904367628123768m_-7630672803956935750moz-cite-prefix">Hi Martin,<br>
      <br>
      i tried the triangle filter in all cases - and yes - i works in
      all three cases. <br>
      <br>
      So is this "problem" of concave polygons inside VTK or in OpenGL?
      <br>
      <br>
      Best regards,<br>
      <br>
            Stefan<br>
    </div>
    <blockquote type="cite">
      
      <div dir="ltr">I'm not sure if this is your issue, but you might
        try using a triangle filter on your data. For OpenGL we do not
        guarantee correct rendering of concave polygons. The triangle
        filter will convert a concave polygon into convex triangles
        which should render correctly.</div>
      <div class="gmail_extra"><br>
        <div class="gmail_quote">On Tue, Oct 18, 2016 at 2:20 AM, Stefan
          Melber <span dir="ltr"><<a href="mailto:Stefan.Melber@dlr.de" target="_blank">Stefan.Melber@dlr.de</a>></span>
          wrote:<br>
          <blockquote class="gmail_quote">
            <div> Hi,<br>
              <br>
              i found a rendering problem with cuts through polyhedral
              cells depending on which rendering backend is used. For
              example in PV 5.1.2 compiled with<br>
              <br>
              VTK_RENDERING_BACKEND = OpenGL<br>
              <br>
              a cut looks like error.opengl.v5_1_2.png - there is a
              wrong shading and some facets coming from the wrong
              starting point.<br>
              <br>
              Switching to OpenGL2 everything is fine
              (error.opengl2.v5_1_2.png). This problem is the same with
              ParaView 5.2.0RC1 and OpenGL or OpenGL2 - however there
              seems to be an additional (smaller) problem using OpenGL2:
              there are some lines drawn outside of the shell - see
              error.opengl2.v5_2_0rc1.png (cutted on a different
              position).<br>
              <br>
              The example cell is for testing is attached as "error.vtk"
              - cut e.g. in x-direction on different positions to get
              the described effects.<br>
              <br>
              Best regards,<br>
              <br>
                     Stefan<br>
              <br>
              <br>
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        <br><span class="m_-7708904367628123768HOEnZb"><font color="#888888">
        <div><br>
        </div>
        -- <br>
        <div class="m_-7708904367628123768m_-7630672803956935750gmail_signature" data-smartmail="gmail_signature">Ken
          Martin PhD
          <div>Chairman & CFO<br>
            Kitware Inc.<br>
            28 Corporate Drive<br>
            Clifton Park NY 12065<br>
            <a href="tel:518%20371%203971" value="+15183713971" target="_blank">518 371 3971</a>
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</blockquote></div><br><br clear="all"><div><br></div>-- <br><div class="m_-7708904367628123768gmail_signature" data-smartmail="gmail_signature">Ken Martin PhD<div>Chairman & CFO<br>Kitware Inc.<br>28 Corporate Drive<br>Clifton Park NY 12065<br>518 371 3971<div><br></div><div><span style="font-size:10pt;font-family:Tahoma,sans-serif">This communication,
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