[vtkusers] vtkClipClosedSurface problem

[Bill Lorensen]

Randy,

You might also look at the new class
vtkBooleanOperationPolyDataFilter. I don't know if it is applicable
for your application.

Here is an example:
http://www.vtk.org/Wiki/VTK/Examples/Cxx/PolyData/BooleanOperationPolyDataFilter

Bill

On Fri, Mar 30, 2012 at 1:32 PM, David Gobbi <david.gobbi at gmail.com> wrote:
> Hi Randy,
>
> It's not tricky, its picky, as in picky about its input.  Use
> vtkFeatureEdges as I mentioned in my earlier email to test your data
> to verify that it will work.  You might find some interesting things
> about your data if you do so.
>
> The vtkClipClosedSurface code uses a different clipping algorithm as
> compared to vtkClipPolyData.  The latter uses a vtkPointLocator to
> generate its output... this is a bit sloppy, because the point locator
> can sometimes merges points that shouldn't be merged, but it is
> forgiving, and doesn't require anything special about its input.  On
> the other hand, vtkClipClosedSurface does not use a vtkPointLocator,
> instead it uses an algorithm that will never accidentally merge points
> and therefore won't accidentally modify the topology of the data.  In
> other words, given a manifold surface as input, it will give a
> manifold surface as output, which is something that vtkClipPolyData
> cannot guarantee.
>
>  - David
>
>
>
> On Fri, Mar 30, 2012 at 2:11 PM, Randy Heiland <heiland at indiana.edu> wrote:
>> Sadly, the vtkCleanPolyData seems to only fix the problem some of the time.  I updated that web page to show another test case.  In addition to cleaning the output of the superquadsource, I also tried cleaning the output of the glyphs themselves, but it didn't seem to help.  The ClipClosedSurface seems to be one tricky filter.
>>
>> -Randy
>>
>> On Mar 29, 2012, at 10:36 PM, David Gobbi wrote:
>>
>>> Hi Randy,
>>>
>>> I tried it with vtkSphereSource and it worked perfectly.  Evidently
>>> vtkSuperquadricSource does not generate a closed surface.  You can
>>> test whether a surface is closed by using the vtkFeatureEdges filter
>>> to display free edges, i.e. edges that belong to only one polygon.
>>> In a closed surface, each edge belongs to exactly two polygons.
>>>
>>> feature = vtk.vtkFeatureEdges()
>>> feature.SetInputConnection(glyphs.GetOutputPort())
>>> feature.FeatureEdgesOff()
>>> feature.BoundaryEdgesOn()
>>> feature.NonManifoldEdgesOn()
>>>
>>> Try vtkCleanPolyData to clean the output of vtkSuperquadricSource.
>>> It isn't guaranteed to work, but it's worth a shot.
>>>
>>> - David
>>>
>>>
>>> On Thu, Mar 29, 2012 at 6:27 PM, Randy Heiland <heiland at indiana.edu> wrote:
>>>> Hi,
>>>>
>>>> I'm having a problem with this filter and would welcome any advice.  I've got a self-contained example here:
>>>>
>>>> http://old.compucell3d.org/mediawiki1.7/index.php/Vtk_clip_cap_glyphs
>>>>
>>>> thanks, Randy
>>
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