[vtkusers] vtkSmoothPolyDataFilter + unstructuredGrid

[Bill Chivas]

By saying, "on which cells", i mean on the produced polygons (hexahedrons
faces / triangles), or on the hexahedrons.



2009/12/14 Bill Chivas <noo134 at googlemail.com>

> I mean vtkDataSetSurfaceFilter (similar to vtkGeometryFilter).
> At step 3, if i replace it with vtkGeometryFilter, i get only the outer.
>
> vtkSmoothPolyDataFilter on which cells is applied? hexahedrons?
>
>
>
> 2009/12/11 David Gobbi <david.gobbi at gmail.com>
>
>> By "vtkDataSurfaceFilter" you mean "vtkGeometryFilter", right?
>>
>> And no, the interior hexahedrons are definitely not smoothed.  No way
>> no how.  And because of this, some of the inside points might end up
>> on the outside after smoothing, resulting in an invalid data set.
>>
>> You need a step 5 which smooths the interior points, based on the
>> connectivity information.  Such a filter does not exist in VTK, it
>> would have to be written.
>>
>>   David
>>
>>
>> On Fri, Dec 11, 2009 at 9:04 AM, Bill Chivas <noo134 at googlemail.com>
>> wrote:
>> > Thank you both.
>> > I'll try out your suggestions.
>> > By far, i tried the following pipeline:
>> > 1) UnstructuredGrid
>> > 2) vtkShrinkFilter (so i can see the hexahedrons)
>> > 3) vtkDataSetSurfaceFilter (!)
>> > 4) vtkSmoothPolyDataFilter
>> >
>> > I get what i want. I'm not really sure if ALL hexahedrons are smoothed
>> (and
>> > not only the outer ones).
>> > What do you think?
>> >
>> > Thanks,
>> > Bill
>> >
>> >
>> >
>> > 2009/12/11 David Gobbi <david.gobbi at gmail.com>
>> >>
>> >> Hmm... if GeometryFilter keeps all the points, then it's possible that
>> >> you could generate a new vtkDataSet that combines the points from the
>> >> smoothed polydata with the cells of your grid.  Something like this:
>> >>
>> >> smoothFilter->Update();
>> >> gridProducer->Update();
>> >> vtkDataSet *newdata = vtkDataSet::New();
>> >> newdata->DeepCopy(gridProducer->GetOutput());
>> >> newdata->SetPoints(smoothFilter->GetOutput()->GetPoints());
>> >>
>> >> Note that code like this can crash if the assumptions aren't correct.
>> >> Also, only the outer layer of points will be smoothed, so the
>> >> resulting data object might contain invalid cells.  But still, this
>> >> should give you ideas about how to find a proper solution.
>> >>
>> >>    David
>> >>
>> >>
>> >> On Fri, Dec 11, 2009 at 8:40 AM, Bill Chivas <noo134 at googlemail.com>
>> >> wrote:
>> >> > vtkGeometryFilter works fine. I wonder if i could get back to
>> >> > unstructuredGrid and hexahedrons by using the points.
>> >> > I noticed that the number of points are the same in unstructuredGrid
>> and
>> >> > vtkGeometryFilter (vtkPolyData).
>> >> > Could i "reproduce" the original hexahedron topology?
>> >> >
>> >> > Thanks,
>> >> > Bill
>> >> >
>> >> > 2009/12/11 David Gobbi <david.gobbi at gmail.com>
>> >> >>
>> >> >> On Fri, Dec 11, 2009 at 7:11 AM, Bill Chivas <noo134 at googlemail.com
>> >
>> >> >> wrote:
>> >> >> > Hello all,
>> >> >> >
>> >> >> > I would like to use vtkSmoothPolyDataFilter  on an
>> unstructuredGrid,
>> >> >> > but
>> >> >> > i
>> >> >> > read the particular filter applies only to vtkPolyData.
>> >> >> > My unstructuredGrid consists of hexahedrons.
>> >> >> > How could i use the filter?
>> >> >> > One idea i thought is to extract the surface iterately and apply
>> to
>> >> >> > these
>> >> >> > surfaces, but i don't know if it's ok.
>> >> >>
>> >> >> I've seen some people create a "skin" polydata with
>> vtkGeometryFilter,
>> >> >> apply the smoothing to the "skin" and then use a custom filter to
>> >> >> propagate the smoothing throughout the interior of their mesh.  The
>> >> >> vtkGeometryFilter is a basic anything-to-polydata filter, so it is
>> >> >> easy to use.  The final step of using the smoothed polydata to
>> create
>> >> >> a smoothed mesh is nontrivial, though.
>> >> >>
>> >> >>    David
>> >> >
>> >> >
>> >
>> >
>>
>
>
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