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<div class=Section1><pre><font size=2 face="Courier New"><span
style='font-size:10.0pt'>Thanks a lot Dave,<o:p></o:p></span></font></pre><pre><font
size=2 face="Courier New"><span style='font-size:10.0pt'>I actually already found the codepiece before but didn’t believe the function<o:p></o:p></span></font></pre><pre><font
size=2 face="Courier New"><span style='font-size:10.0pt'>EvaluateFunction would do the trick. Now it works but very slow of course. <o:p></o:p></span></font></pre><pre><font
size=2 face="Courier New"><span style='font-size:10.0pt'>Since I only work with pointdata (vtkImageData) I can’t really use your advice to speed up the process. Or am I wrong and should test cells?<o:p></o:p></span></font></pre><pre><font
size=2 face="Courier New"><span style='font-size:10.0pt'>First I’ll try to use vtkThreadedImageAlgorithm instead of vtkImageAlgorithm to use multicores.<o:p></o:p></span></font></pre><pre><font
size=2 face="Courier New"><span style='font-size:10.0pt'>Then I think I need something like octree to exclude a lot of points from calculation.<o:p></o:p></span></font></pre><pre><font
size=2 face="Courier New"><span style='font-size:10.0pt'>I’ve seen there already exist: vtkHyperOctree hope I can use it for the task.<o:p></o:p></span></font></pre><pre><font
size=2 face="Courier New"><span style='font-size:10.0pt'><o:p> </o:p></span></font></pre><pre><font
size=2 face="Courier New"><span style='font-size:10.0pt'>Btw: Why does posting to the forum always opens up a new thread? I click on the email-address of the last poster in the thread, it opens Office and should<o:p></o:p></span></font></pre><pre><font
size=2 face="Courier New"><span style='font-size:10.0pt'>Have gotten information “in-reply-to …” but still it doesn’t work.<o:p></o:p></span></font></pre><pre><font
size=2 face="Courier New"><span style='font-size:10.0pt'><o:p> </o:p></span></font></pre><pre><font
size=2 face="Courier New"><span style='font-size:10.0pt'>Regards and thanks again<o:p></o:p></span></font></pre><pre><font
size=2 face="Courier New"><span style='font-size:10.0pt'><o:p> </o:p></span></font></pre><pre><font
size=2 face="Courier New"><span style='font-size:10.0pt'>Michael<o:p></o:p></span></font></pre><pre><i><font
size=2 face="Courier New"><span style='font-size:10.0pt;font-style:italic'><o:p> </o:p></span></font></i></pre><pre><i><font
size=2 face="Courier New"><span style='font-size:10.0pt;font-style:italic'><o:p> </o:p></span></font></i></pre><pre><i><font
size=2 face="Courier New"><span style='font-size:10.0pt;font-style:italic'><o:p> </o:p></span></font></i></pre><pre><i><font
size=2 face="Courier New"><span style='font-size:10.0pt;font-style:italic'><o:p> </o:p></span></font></i></pre><pre><i><font
size=2 face="Courier New"><span style='font-size:10.0pt;font-style:italic'><o:p> </o:p></span></font></i></pre><pre><i><font
size=2 face="Courier New"><span style='font-size:10.0pt;font-style:italic'>To answer your original question: look at line 557. This tests a point<o:p></o:p></span></font></i></pre><pre><i><font
size=2 face="Courier New"><span style='font-size:10.0pt;font-style:italic'>against the plane equations that define the frustum (when this->ExactTest is<o:p></o:p></span></font></i></pre><pre><i><font
size=2 face="Courier New"><span style='font-size:10.0pt;font-style:italic'>off).<o:p></o:p></span></font></i></pre><pre><i><font
size=2 face="Courier New"><span style='font-size:10.0pt;font-style:italic'><o:p> </o:p></span></font></i></pre><pre><i><font
size=2 face="Courier New"><span style='font-size:10.0pt;font-style:italic'>If you decide to backport ExtractSelectedFrustum this explanation may help.<o:p></o:p></span></font></i></pre><pre><i><font
size=2 face="Courier New"><span style='font-size:10.0pt;font-style:italic'>The algorithm it uses (when this->ExactTest is on) comes from Ned Greene,<o:p></o:p></span></font></i></pre><pre><i><font
size=2 face="Courier New"><span style='font-size:10.0pt;font-style:italic'>Graphics Gems IV, 1994, p 74-82. What it does is, instead of testing each<o:p></o:p></span></font></i></pre><pre><i><font
size=2 face="Courier New"><span style='font-size:10.0pt;font-style:italic'>vertex of a cell against all six plane equations that define the frustum,<o:p></o:p></span></font></i></pre><pre><i><font
size=2 face="Courier New"><span style='font-size:10.0pt;font-style:italic'>you can determine which vertex is nearest and farthest to each of the<o:p></o:p></span></font></i></pre><pre><i><font
size=2 face="Courier New"><span style='font-size:10.0pt;font-style:italic'>planes. By testing just those two vertices against the plane equations you<o:p></o:p></span></font></i></pre><pre><i><font
size=2 face="Courier New"><span style='font-size:10.0pt;font-style:italic'>can quickly reject the cells that are completely outside of the frustum and<o:p></o:p></span></font></i></pre><pre><i><font
size=2 face="Courier New"><span style='font-size:10.0pt;font-style:italic'>quickly accept the cells that are completely inside the frustum. The cells<o:p></o:p></span></font></i></pre><pre><i><font
size=2 face="Courier New"><span style='font-size:10.0pt;font-style:italic'>that are neither completely in or out are then clipped to determine if they<o:p></o:p></span></font></i></pre><pre><i><font
size=2 face="Courier New"><span style='font-size:10.0pt;font-style:italic'>really do intersect.<o:p></o:p></span></font></i></pre><pre><i><font
size=2 face="Courier New"><span style='font-size:10.0pt;font-style:italic'><o:p> </o:p></span></font></i></pre><pre><i><font
size=2 face="Courier New"><span style='font-size:10.0pt;font-style:italic'>In either case when the PassThrough flag is on, it runs through each cell,<o:p></o:p></span></font></i></pre><pre><i><font
size=2 face="Courier New"><span style='font-size:10.0pt;font-style:italic'>uses one of the above options to determine if it is in or not and then puts<o:p></o:p></span></font></i></pre><pre><i><font
size=2 face="Courier New"><span style='font-size:10.0pt;font-style:italic'>that result into the vtkInsidedness array.<o:p></o:p></span></font></i></pre><pre><i><font
size=2 face="Courier New"><span style='font-size:10.0pt;font-style:italic'><o:p> </o:p></span></font></i></pre><pre><i><font
size=2 face="Courier New"><span style='font-size:10.0pt;font-style:italic'>To test if a dataset has that array just do:<o:p></o:p></span></font></i></pre><pre><i><font
size=2 face="Courier New"><span style='font-size:10.0pt;font-style:italic'> vtkDataArray *insidedness = ds->GetCellData()->GetArray("vtkInsidedNess);<o:p></o:p></span></font></i></pre><pre><i><font
size=2 face="Courier New"><span style='font-size:10.0pt;font-style:italic'>//or GetPointData as the case may be<o:p></o:p></span></font></i></pre><pre><i><font
size=2 face="Courier New"><span style='font-size:10.0pt;font-style:italic'> if (insidedness == NULL)<o:p></o:p></span></font></i></pre><pre><i><font
size=2 face="Courier New"><span style='font-size:10.0pt;font-style:italic'> {<o:p></o:p></span></font></i></pre><pre><i><font
size=2 face="Courier New"><span style='font-size:10.0pt;font-style:italic'> cerr << "It doesn't have it."<o:p></o:p></span></font></i></pre><pre><i><font
size=2 face="Courier New"><span style='font-size:10.0pt;font-style:italic'> }<o:p></o:p></span></font></i></pre><pre><i><font
size=2 face="Courier New"><span style='font-size:10.0pt;font-style:italic'><o:p> </o:p></span></font></i></pre><pre><i><font
size=2 face="Courier New"><span style='font-size:10.0pt;font-style:italic'>cheers,<o:p></o:p></span></font></i></pre><pre><i><font
size=2 face="Courier New"><span style='font-size:10.0pt;font-style:italic'>Dave DeMarle<o:p></o:p></span></font></i></pre>
<p class=MsoNormal><i><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial;font-style:italic'><o:p> </o:p></span></font></i></p>
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