You are right, polydata is intended to describe 0D (vertices), 1D (lines) and 2D (polygons) cell. Tetrahedrons are the "simplest" 3D cells, such as triangles are the "simplest" 2D cells, but vtkPolyData cannot have 3D cells. However, a tetrahedron is composed of 4 vertices, 6 edges (lines) and 4 triangles (polygons) that you can *represents* thanks to a vtkPolyData. when you render a tetrahedral mesh through a polydata, you don't "see" the tetrahedrons, but their bounds.<br>
<br><br>Jerome<br><br><div class="gmail_quote">2009/12/11 Baliki B. <span dir="ltr"><<a href="mailto:balikivtk@gmail.com">balikivtk@gmail.com</a>></span><br><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
I tried vtkShrinkFilter and it worked. My question is why using vtkShrinkFilter and pressing w key shows tetrahedrons and without it(e.g. using the original unstructured grid) doesn't? Is it something with the fact you say it results in "polydata" ?<br>
<br>Why you give emphasis in "results in polydata" in both first two methods (vtkShrinkFilter and vtkExtractGeometry) ? Is something "wrong" the polydata we get?<br><br>Also, i read in the book that polydata is types(vertices, lines, polygons and triangle strips) which is limited and that's why we use unstructured grid to represent a tetrahedron. <br>
Am i missing something?<div><div></div><div class="h5"><br><br><div class="gmail_quote">2009/12/10 Dominik Szczerba <span dir="ltr"><<a href="mailto:dominik@itis.ethz.ch" target="_blank">dominik@itis.ethz.ch</a>></span><br>
<blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
Unfortunately, I will not have a possibility to write those examples this time. A few quick comments follow below.<div><br>
<br>
David Doria wrote:<br>
<blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
On Thu, Dec 10, 2009 at 8:52 AM, Baliki B. <<a href="mailto:balikivtk@gmail.com" target="_blank">balikivtk@gmail.com</a>> wrote:<br>
<blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
Could you explain (with some code) a little bit more?<br>
<br>
<br>
2009/12/10 Dominik Szczerba <<a href="mailto:dominik@itis.ethz.ch" target="_blank">dominik@itis.ethz.ch</a>><br>
<blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
You can see your tets in multiple ways:<br>
<br>
- extract cells by region<br>
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There is a filter (vtkExtractGeometry) to extract parts of a volume mesh NOT cutting the cells. Resulting is a polydata of course, but you see the inside cells otherwise hidden. Combined with an interactive widget (e.g. vtkBoxWidget) and edge visibility it gives a very good view.<br>
<br>
<blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;"><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
<blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
- cell shrinking<br>
</blockquote></blockquote></blockquote>
<br>
You can shrink all the cells by a factor (vtkShrinkFilter). This will result in a polydata again, but you will see the separate cells (by their 4 shrinked triangles).<div><br>
<br>
<blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;"><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
<blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
<br>
To see the associated data:<br>
- volume rendering<br>
</blockquote></blockquote></blockquote>
<br></div>
see vtkVolume<br>
<br>
<blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;"><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
<blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
- cut slices<br>
</blockquote></blockquote></blockquote>
<br>
see vtkCutter<br>
<br>
<blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;"><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
<blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
- clip<br>
</blockquote></blockquote></blockquote>
<br>
see vtkClipDataSet<br>
<br>
<blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;"><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
<blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
- contouring<br>
</blockquote></blockquote></blockquote>
<br>
see vtkContourFilter<br><font color="#888888">
<br>
Dominik</font><div><div></div><div><br>
<br>
<blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;"><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
<blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
<br>
Dominik<br>
<br>
</blockquote>
<br>
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</blockquote>
<br>
It's sounding like this may call for a couple of examples...<br>
<br>
Thanks,<br>
<br>
Captain Example<br>
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