This is an inherent limitation in the algorithm. <br><br>The hardware selector, and it predecessor vtkVisibleCellSelector, render an image and determine what cell was drawn behind each pixel. I said cell not cells because there is no way to recover more than one cell from the color of any given pixel. The only workaround I know of is to increase the screen size as you are already doing.<br>
<br>There might be some sort of topological walk algorithm that would produce an exact result but I am not aware of one and suspect that it will be orders of magnitude slower than the rendering based algorithm we have now. A frustum selection will produce an exact result and do it fairly quickly, but it does not and can not determine which cells are visible and which are not.<br>
<br>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 class="gmail_quote">On Mon, Oct 18, 2010 at 9:10 AM, <span dir="ltr"><<a href="mailto:s61500@htw-dresden.de">s61500@htw-dresden.de</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;">
<div class="im">I think pictures will be the best illustration of the problem.<br>
<br>
</div><a href="http://www2.htw-dresden.de/%7Es61500/example_sphere.png" target="_blank">http://www2.htw-dresden.de/~s61500/example_sphere.png</a><br>
<div class="im"><br>
1. window --> viewport<br>
2. window --> result with RenderWindow size of [300, 300]<br>
3. window --> result with RenderWindow size of [1000, 1000]<br>
4. window --> result with RenderWindow size of [1000, 1000]<br>
<br>
</div><a href="http://www2.htw-dresden.de/%7Es61500/example_testobject.png" target="_blank">http://www2.htw-dresden.de/~s61500/example_testobject.png</a><br>
<div class="im"><br>
1. window --> viewport<br>
1. row --> result with RenderWindow size of [300, 300]<br>
2. row --> result with RenderWindow size of [1000, 1000]<br>
<br>
</div><a href="http://www2.htw-dresden.de/%7Es61500/example_testobject2.png" target="_blank">http://www2.htw-dresden.de/~s61500/example_testobject2.png</a><br>
<div><div></div><div class="h5"><br>
- detailed view of the problem<br>
<br>
I hope that the screenshots clarify the problem in the best way.<br>
<br>
Stefan<br>
<br>
> Can you clarify what you mean by the result isn't right?<br>
><br>
> 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>
> On Sun, Oct 17, 2010 at 1:12 PM, <<a href="mailto:s61500@htw-dresden.de">s61500@htw-dresden.de</a>> wrote:<br>
><br>
>> Hi,<br>
>><br>
>> upon finding the error in the example code I noted that the result<br>
isn't right.<br>
>><br>
>> The example code can you find here:<br>
>><br>
>> <a href="http://www.vtk.org/Wiki/VTK/Examples/Cxx/Broken/Filtering/ExtractVisibleCells" target="_blank">http://www.vtk.org/Wiki/VTK/Examples/Cxx/Broken/Filtering/ExtractVisibleCells</a><br>
>><br>
>> I find out that you get a better result when you set the size of the<br>
vtkRenderWindow higher.<br>
>> But with a size of [1000,1000] I don't get a perfect result by my test<br>
sphere object with 27.000 triangles. To set the window size high enough<br>
couldn't be the right way, because the program will work with nets of 1<br>
million triangles.<br>
>><br>
>> So my question, is there another way to get a better result without set<br>
the window size higher?<br>
>><br>
>> Stefan<br>
>><br>
>> _______________________________________________<br>
>> Powered by <a href="http://www.kitware.com" target="_blank">www.kitware.com</a><br>
>><br>
>> Visit other Kitware open-source projects at<br>
>> <a href="http://www.kitware.com/opensource/opensource.html" target="_blank">http://www.kitware.com/opensource/opensource.html</a><br>
>><br>
>> Please keep messages on-topic and check the VTK FAQ at:<br>
>> <a href="http://www.vtk.org/Wiki/VTK_FAQ" target="_blank">http://www.vtk.org/Wiki/VTK_FAQ</a><br>
>><br>
>> Follow this link to subscribe/unsubscribe:<br>
>> <a href="http://www.vtk.org/mailman/listinfo/vtkusers" target="_blank">http://www.vtk.org/mailman/listinfo/vtkusers</a><br>
>><br>
><br>
<br>
<br>
<br>
</div></div></blockquote></div><br>