<div>In general the output of this type of operation has to be either vtkUnstructuredGrid or vtkPolyData because when you take an arbitrary subset out of a structured data set you loose the regularity. </div>
<div> </div>
<div>vtkExtractVOI pulls out aligned "slabs" out of structured datasets and because the slabs are aligned in ijk space it's output can stay structured. </div>
<div> </div>
<div>If you have to keep it structured your only option is to create an inside/outside data array. You can threshold on that later if you need to, but again that will produce an unstructured dataset. I think vtkProbeFilter and vtkSampleFunction both can be used to create the "insidedness" array. Others options likely exist too.</div>
<div><br clear="all">David E DeMarle<br>Kitware, Inc.<br>R&D Engineer<br>28 Corporate Drive<br>Clifton Park, NY 12065-8662<br>Phone: 518-371-3971 x109<br><br><br></div>
<div class="gmail_quote">On Sat, Sep 19, 2009 at 10:13 AM, Robin Zhao <span dir="ltr"><<a href="mailto:zhaoyoubing@gmail.com">zhaoyoubing@gmail.com</a>></span> wrote:<br>
<blockquote style="BORDER-LEFT: #ccc 1px solid; MARGIN: 0px 0px 0px 0.8ex; PADDING-LEFT: 1ex" class="gmail_quote">
<div>Hi, Dear vtk guys,</div>
<div> </div>
<div>I met some difficulties on selecting voxels inside a user defined implicit function.</div>
<div> </div>
<div>I have studied vtkExtractGeometry, but its output is unstructured grid.</div>
<div> </div>
<div>I also studied vtkSelection which seems not to support vtkImplicitFunction.</div>
<div> </div>
<div>Are there any possible methods to do it in the framework of vtk, </div>
<div>or do I need to do it by myself.</div>
<div> </div>
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